Focus Problem - 350XT - 50/1.8 II

[RAitch]

So, I know there have been other posts, but here's my example.

I'm having some unexpected results with my 50mm1.8. I've been taking a bunch of pictures of my son and were dissapointed in how many were soft and out of focus. At first I figured it had something to do with camera shake and baby motion.

I tried a second time with a tripod and he was on the change table. I was shooting down on him so distance wasn't changing. Everything looked nice and sharp in the viewfinder.
When I reviewed the pictures, most of them were out of focus. (with or without on-cam flash)

Trying to figure this out, I did some experimentation. Here's a sample pic (50% crop). I was focussing on the eye in the red square. (don't comment on composition etc. It's just a test shot of crap on the table).
As you can see, that is not the focus point. Items closer to the camera seem to be in focus (like the yellow finger puppet).

I had my tripod about 3 feet away using natural light. Av mode at 1.8.

I like the lens, but I'm finding I can't get any close shots in focus.
Is anybody else finding the same results? Is this to be expected?

[mr.photoguy]

I learned this the hard way.
At 1.8 the DOF is really shallow.
I found it better to MF on the area that you want in focus, and then take the photo. When you MF with the camera, you will see the Area Of Focus moving. Then take the photo, and zoom in on the LCD to check for sharpness.
I actually like to shoot at 2.8 or 3.2, or so. I rarely shoot at 1.8 to be honest.

Try to manual focus, and then post your results. you should notice the differrence then.

[RAitch]

No difference! I tried that at the same time and got the same results. I know it's narrow, but I find myself using 1.8 FOR the narrow depth of field. Sometimes it fits.

I actually took most of the pictures of my son in manual... and that's why I started experimenting.

After locking in on auto focus, I switched to manual and went back and forth. Yup, auto looked locked in to me.
Also, I tried in manual mode holding the * button for focus lock (CF4) and took a picture when the focus lock lit up.
Same results there too.

[Jackal]

I've borrowed my friend's 50mm 1.8 and it's a SUPER NICE lens. I had no problems like this at all.

Maybe you have the camera set to pick whichever focus point it deems more important? It looks like the camera picked whichever focus point is on that yellow puppet?

I always have my camera set to the middle focus point.

[Meg C]

I haven't had any issues with mine, and find that it focuses beautifully on the focus point. Are you saying that the red focus light was actually flashing and focused on the eye in your pic, and looked clear when you took the shot? When in auto mode, my focus point did flip flop around when trying out this lens. Did you manually select the point?

[RAitch]

I have the focus point locked on the center dot (my wife doesn't like the roaming mode).
In this shot, I had the center dot (active) centered where the red square in the pic is. The red box was centered in the pic... when I cropped to post, it ended up in the corner.

I tried all of these options. With the center point locked on the eye, I tried the AF mode. Got a lock and it looked sharp in focus. Took the pic.

I also tried manual focus. I focussed in and out until the eye looked sharp. Took the shot.

Last, I tried in manual mode holding the focus (*) button down. When the focus point lit up, I took the shot.

In all 3 cases, the picture turned out like this.

[RAitch]

Here's a screen capture from the ZoomBrowser. The red square isn't obviously that big, but it just the ZoomBrowser showing which focus point was in focus.

The center point was perfectly centered on the right eye and was lit up.
As you can see, the focus zone doesn't appear to be in the right area.

[Bob_A]

Wow, at first I thought you may have shot this hand-held, but I see you mention that you used a tripod. Was this shot using only the center focus point?

edit:

You posted the entire pic as I was wiritng this:D . Sure looks like you have a real issue. Also, at 3 ft the DOF for reasonable sharpness is about .4" in front of the focus point and .5" behind the focus point ... so it doesn't have to be off by much.

Bob

[mr.photoguy]

No difference! I tried that at the same time and got the same results. I know it's narrow, but I find myself using 1.8 FOR the narrow depth of field. Sometimes it fits.

I actually took most of the pictures of my son in manual... and that's why I started experimenting.

After locking in on auto focus, I switched to manual and went back and forth. Yup, auto looked locked in to me.
Also, I tried in manual mode holding the * button for focus lock (CF4) and took a picture when the focus lock lit up.
Same results there too.edit :

Just read the rest of your post.

Use manual focus until you see the eye come in focus, not until you see the Red dot highlighted.

[RAitch]

I sure did use a tripod, but didn't use my homemade shutter release (as you can see in the bottom right).

I've had the same results without touching the camera (using the release). I was really careful to not shake the camera while pressing the button. But there are points in the picture that are in focus, so I don't think shake is the issue.

[RAitch]

Don't rely on the focus lamp to light up. Look at the eye of the image, and see when its in focus, and then take the photo quickly. also watch your shutter speed to make sure it's over 1/50th .. use higher than 1/50th.

As I mentioned, I tried it 3 different ways... one was without using auto or the focus assist.

I think this pic was 1/80.

[mr.photoguy]

As I mentioned, I tried it 3 different ways... one was without using auto or the focus assist.

I think this pic was 1/80.
sorry, I edited the post.

[jimsolt]

It looks to me as though the eye in the red square is NOT in focus. The lower right of the picture appears to be sharper. Depth of field would be measured in inches at f1.8.
I was shooting an orchid yesterday with the same lens and the same camera at f1.8 and parts of the bloom were in focus and parts out of focus. I had to stop down to get the whole flower in focus.
I also found that manual focus gave me more accurate focusing on the part of the shot I wanted in focus.
Jim

[GyRob]

If your focusing on the eye in the square dof has nothing to do with how sharp it is , It should be Sharp at that Point regardles of dof. as thats your point of focus. looks like a fault to me.
Rob.

[RAitch]

I know Jim, I like the manual focus too because it's flexible. I'm purposely leaving at 1.8 for these tests because I noticed there was a problem.

Here's another *extreme* shot. (they're not all this bad, but generally have an area in frame that's sharp). Yes, I was using a tripod for this too, so it's not camera shake or changing distance. (Changing distance = focussing then moving closer/farther without realizing)

His eyes were in focus in the viewfinder... but after the shot, they weren't.

[mr.photoguy]

I will do a ruler shot in a few minutes, if I can find my dang tape measure.

--

[RAitch]

I was also playing with the diopter adjuster... but couldn't see how that would affect the focus of the image. I have good eyes that can focus on the image through 80% of the range. It didn't seem to matter where I had that set.

[RAitch]

Funny thing about the ruler shot. I did several of them the other day and had good results. One however was shifted to the foreground an inch.

It's not necessarily ALL shots. Sometimes I get lucky or something.

[Bob_A]

Focus can be off a bit (but not this much) and still be considered to be acceptable by Canon for consumer bodies (i.e., focus has to be within the DOF). For your case the focus is outside the DOF, so you will need to send the camera to Canon for calibration.

The problem is likely with the camera body and not the lens.


Bob

Bob

[Bob_A]

Funny thing about the ruler shot. I did several of them the other day and had good results. One however was shifted to the foreground an inch.

It's not necessarily ALL shots. Sometimes I get lucky or something.


Hmmm ... that now makes me think that it is the lens. To me, if the camera is off ... it's off all the time (just an adjustment). I wonder if the focus mechanism in the lens is jumping a bit after focus lock has been achieved? Someone else with a 24-70L was complaining about this on this forum a few days ago.

[RAitch]

Hmmm... I didn't notice any problems with the kit lens or the 70-200. I know they're not as fast, but I figured I'd see something.

I've been impressed with the sharpness and clarity so far, but havn't really been outside in daylight to do some testing.

[RAitch]

Hmmm ... that now makes me think that it is the lens. To me, if the camera is off ... it's off all the time (just an adjustment). I wonder if the focus mechanism in the lens is jumping a bit after focus lock has been achieved? Someone else with a 24-70L was complaining about this on this forum a few days ago.

That makes me feel better... but that wouldn't explain why it still is out when I'm using Av on MF and bypass any auto focussing.

I'm not sure what's wrong, but I appreciate everybody's help.

I'll do some more testing I guess.
Any recommendations for tests? I can do some more ruler shots. Should I try with and without the on camera flash?

[Bob_A]

Try this site:

http://www.photo.net/learn/focustest/

I wonder what would happen if you tried the following:

1. Focus behind the subject in manual, then use autofocus and shoot
2. Focus in front of the subject in manual, then use autofocus and shoot

It would be interesting if the focus problem depends on what direction the focus mechanism needs to move (i.e., something sticks or jumps in one direction). However your comment about not even getting consistent results in MF puzzles me.

Bob

[avdh20]

So, I know there have been other posts, but here's my example.

I'm having some unexpected results with my 50mm1.8. I've been taking a bunch of pictures of my son and were dissapointed in how many were soft and out of focus. At first I figured it had something to do with camera shake and baby motion.

I tried a second time with a tripod and he was on the change table. I was shooting down on him so distance wasn't changing. Everything looked nice and sharp in the viewfinder.
When I reviewed the pictures, most of them were out of focus. (with or without on-cam flash)

Trying to figure this out, I did some experimentation. Here's a sample pic (50% crop). I was focussing on the eye in the red square. (don't comment on composition etc. It's just a test shot of crap on the table).
As you can see, that is not the focus point. Items closer to the camera seem to be in focus (like the yellow finger puppet).

I had my tripod about 3 feet away using natural light. Av mode at 1.8.

I like the lens, but I'm finding I can't get any close shots in focus.
Is anybody else finding the same results? Is this to be expected?

Man I thought I was the only one. I just got my 50 1.8 too, and i cant get it to focus for the life of me. When it does focus, it focuses about an inch to the right of where i have it focused (when all the way open). I seems though when I move it to f/4 its fine. I really dont have an explanation for what the problem is as 1.8. I wish i knew. I dont know why they would make a lense that fast if it doesnt perform. Why do people buy the 50 f/1.4? I just feel clueless just like you. :rolleyes: Well good luck and if you come up with any solutions let me know.

~aj

[Dante King]

I may be way off base here. Are you taking your finer off the shutter button momentarily before releasing the sutter? Might explain losing AF. This wont be possible in P or Auto mode as you cant snap w/o focus lock. Hummm..... I can say my 50mm is painfully sharp and spot on.

[funpix]

It is maybe my inexperience but it if your lens is really not right can you not return it to where you purchased for an exchange?

[RAitch]

Bob A: I'll have a look at that site in a bit. I'll also try your idea out tomorrow when the natural light returns. I'll manually focus at the object, then adjust behind and use auto focus to see what happens... then the same thing just forwards. I'll post the results.
(like you said, that doesn't explain full manual problems... but I'd still like to see the results of your theory)

AVDH20: There's somebody else? OK, maybe we're just doing something wrong or there's an option that's screwed up somewhere. Maybe now with all this attention we can get to the bottom of this. It's making me feel better that you're having the same problem on a different body. That makes me feel like it's lens related.
Do you only have problems when you're as tight and close as possible? Maybe it has problems if it's so close... maybe the light rays reflect differently for this lens and show an in focus image in the viewfinder (through mirrors) but actually has a different focal range for the sensor or something silly.

Dante King: I wasn't removing my finger from the button to lose AF. Since I was aiming the center sensor on the eye and had the camera locked in on the tripod, I half pressed for the beep (got a lock), waiting a split second, then continued to press the button in for the shot.
Also, that should have nothing to do with MF... since autofocus is never engaged.
Any other ideas??? Seriously, keep them coming!!

Funpix: I could return it (maybe since it was a "special order" -- "nobody orders these lenses any more" the guy tells me) but I want to make sure that there is a problem with the lens before I do that. I don't want to go through return hassles if I don't have to... especially if I just end up with a lens that does the same thing.


Like I said, I'll do some more tests tomorrow when it's light out again. I want to test with natural light again.

For those who have a pin sharp 1.8, please post some shots at f1.8 so we can see how our should look. If you can use Manual focus on Av without flash (not sure if that will change things) that would be sweet!!! Ruler test... or whatever.

(THANKS EVERYBODY... Keep the ideas and info coming.)

[Dante King]

here is a link to a unPSCSed 50mm1.8
http://photography-on-the.net/forum/showthread.php?t=62767

[Skip Souza]

Funpix: I could return it (maybe since it was a "special order" -- "nobody orders these lenses any more" the guy tells me) ....................


(THANKS EVERYBODY... Keep the ideas and info coming.)

I guess I am just another nobody. How rude!
I have not had any problems with mine but I haven't put it through it's paces like you have. I hope you get it sorted out. Good luck and I'll keep reading this thread.

[RAitch]

Yeah, after reading this forum (and thousands of reviews) I was shocked when he 'claimed' that nobody orders the 50s. It seemed like EVERYBODY had one.

I think it was just a store thing... they usually stock the Optex cheap stuff and most people are happy with that. I had to special order some Hoya filters before.

With the exception of most people here, I think if the average person drops over $1500CAD for a camera, they won't spend more money on glass. Me... I bought the camera with the kit lens and added the 70-200 and 50/1.8 at the same time. The 70-200 came with the camera 2 days later, but the 50 took another 2 weeks.

[RAitch]

Here's my first test shot. The quality kinda sucks due to JPEG compression and Fotopic upload. Somehow, it looks worse after uploading to Fotopic.
http://images.fotopic.net/?iid=y8fjmh&outx=600&noresize=1&original=1&nostamp=1

Results with ISO 800 and faster shutter speeds (1/250 @ F1.8) produced identical results.

Camera set-up 16 inches from focus point, slightly elevated.
Shot at 45 degrees to ruler.
Indirect natural light (10am-ish) from West coming through window. (No flash)
Middle focus dot centered around 30" mark (don't ask why the ruler is up side down).
Lens in MF mode and manually adjusted focus using view finder.
Shot in Av mode using a shutter release and tripod.

[RAitch]

Upon further review, I noticed something interesting.
At F3.2, everything looks balanced. (compare 29 with 31, 28 with 32, and 27 with 33)
At F2.8, the DOF seems to slip a bit forward.
This shift remains (or is amplified) as you get down to 1.8.
http://images.fotopic.net/?iid=y8fl89&outx=600&noresize=1&original=1&nostamp=1

Now, for those that are going to suggest that either the camera moved or the focus changed, check out the ISO 800 images that were taken IMMEDIATELY after (from 3.2 down to 1.8 )
http://images.fotopic.net/?iid=y8fl8d&outx=600&noresize=1&original=1&nostamp=1

Interesting eh? After the ISO 100 shots, I started at 3.2 and it seems to be centered again... but then as I got down to 1.8, it shifts back.

[RAitch]

OK, More shots.
http://images.fotopic.net/?iid=y8fna5&outx=600&noresize=1&original=1&nostamp=1
I manually focussed on the clown's face and took the first shot. Then I manually focussed in front of the clown and took an AF shot. Then I manually focussed behind the clown and took an AF shot.
I think I need to double-check if I focussed in front first... I'm starting to doubt myself.

Here's another example. Focus is centered on the eye to the left.
http://images.fotopic.net/?iid=y8fnaf&outx=600&noresize=1&original=1&nostamp=1

As you can see, my manuall focussing (main images) is suffering for some reason.

[Bob_A]

Middle focus dot centered around 30" mark (don't ask why the ruler is up side down).


Think ya meant "centimeter" mark not "inches" :D

Bob

[RAitch]

Umm.. ya! What was I smokin'?

[Bob_A]

RAitch,

Does it look to you that for all of the ruler shots that the 30cm mark is within the DOF? If that is the case, this would indicate that the lens is performing within Canon tolerances.

Just curious why your ruler shots all seem to be pretty much in focus (i.e., within DOF), but your clown shot in MF wasn't within the DOF. It also looks like the camera on AF is getting it right, with some small differences. The one you labeled AF from back looks tack sharp.

For the moose picture, again the AF pics look reasonable, with "AF from back" being the winner. MF is ... well ... "off".

I can't explain why your MF pics are so far off. Technique problem? How could this be unless you have shakey hands and are consistently moving the focus ring each time before taking the shot? So strange ...

One thing, for the MF shots are you basing the focus on what you see in the viewfinder or on when the AF point lights up?

Bob

[avdh20]

Hey there, well I have problems with being close and further away, but like you say it seems to get better when your not as open. But then whats the use of 1.8? Right. I'll keep reading on and if I find anything, Ill let you know. I honestly think its my camera though, I also have problem with just focusing in general, on other lenses too.

[RAitch]

RAitch,

I can't explain why your MF pics are so far off. Technique problem? How could this be unless you have shakey hands and are consistently moving the focus ring each time before taking the shot? So strange ...

One thing, for the MF shots are you basing the focus on what you see in the viewfinder or on when the AF point lights up?

Bob

Well, for all of these shots (ruler/clown/moose) I set the tripod up, and for manual focus, I manually set it, took my hands away, then used a shutter release to take the shot. I focussed, then hands-off double-checked through the viewfinder. In this case, it can't be the shaky hand thing (although I agree my hands are a touch shaky).

For the MF shots, I was basing everything off of what I was seeing, not the focus lock lights. (or at least for the ruler/clown/moose pics). I did some tests earlier where I tried everything.

Could it be my diopter thingy not being set right?

[Skip Souza]

Yes it could be the diopter adjustment. If that is not properly adjusted then you will never see the correct focus and you will use the lens focus to correct the the out-of-focus condition caused by diopter adjustment. Think if it as putting the wrong prescription glasses the trying to get the right focus. It will look good through the view finder but not be in focus at the sensor.

[Skip Souza]

P.S.
The diopter adjustment is not affected by nor does it affect the auto focus.

[RAitch]

Yes it could be the diopter adjustment. If that is not properly adjusted then you will never see the correct focus and you will use the lens focus to correct the the out-of-focus condition caused by diopter adjustment. Think if it as putting the wrong prescription glasses the trying to get the right focus. It will look good through the view finder but not be in focus at the sensor.

The weird thing is my eyes adjust almost no matter where the diopter is set. If I auto focus then check the viewfinder, it looks in focus.

On a side note, I don't have problems with focus with the 70-200. This might not be a great example, but it's an unaltered image I had at the ready. No sharp mask... only resized... straight from camera.

[Marshy]

This pic of my daughter and her friend was taken last night with 300D , 50mm 1.8 , F2.2, 1/60 . Focus should of been on my daughter , the girl on the left , but as you can see it is her friend on the right who is focussed . Breezebrowser shows the focus points and this confirms focus was on girl on left , very strange !

[Skip Souza]

The problem would be exacerbated when shooting up close and wide open. These conditions create an extremely narrow dof and any problem in seeing the focus will be worse. Sorry man but it appears that under certain conditions the camera is better looking (sees :-) ) better than you.

[Skip Souza]

If you were shooting with multiple active focus points in auto focus then the camers focused on the near girl. If you were in manual focus then your eyes got it wrong.
Are you going to trust your camera or your lying eyes????
Gotta go to a soccer game, good luck. Still watching.

[Marshy]

If you were shooting with multiple active focus points in auto focus then the camers focused on the near girl. If you were in manual focus then your eyes got it wrong.
Are you going to trust your camera or your lying eyes????
Gotta go to a soccer game, good luck. Still watching.
I would probably agree with the bad eyes theory if it wasn,t for the fact that BB shows were i think the focus should be shame because pics are nice and sharp before touching up .

[RAitch]

Marshy, that's exactly what I'm talking about. It all started with pictures of my son. When he was excited, he'd wave his hand around in front of his face and when I look at the pictures, the hands are usually in focus, not his face (which is what I was manually focussing on).

Seems to be a common problem.
I see a lot of people saying that the lens is *tack sharp* but I'm beginning to wonder if that's just a fluke. I can't get a constant result from this lens in practical use. I've come to the realization that we got what we paid for. Sure it's a great lens for the price, but what good is a lens if it won't take a picture as seen in the viewfinder?
The first time I used this lens, I took a series of about 50 shots and I think around 5 looked like they were crisp.. and that's being generous.

[RAitch]

So here's another test.
http://images.fotopic.net/?iid=y8ftkc&outx=600&noresize=1&original=1&nostamp=1

I backed the camera back to about 6 feet. I took a manual shot, then switched to AF and manually focussed close. Then used auto focus, got a lock, and took a shot. Then I manually focussed to the rear, used auto focus to get a lock and took a shot.

What's weird you ask? My manual focus shot is crisp and the auto focus shots are crap. Explain to me how this can happen?

[mr.photoguy]

It's what I have been saying from the get go..

at 1.8 the DOF, and Area Of Focus is so shallow, it is way better to just Manual Focus.

although at 2.8 here is an example.
http://www.pbase.com/brucescott/image/40106377.jpg

[Marshy]

Marshy, that's exactly what I'm talking about. It all started with pictures of my son. When he was excited, he'd wave his hand around in front of his face and when I look at the pictures, the hands are usually in focus, not his face (which is what I was manually focussing on).

Seems to be a common problem.
I see a lot of people saying that the lens is *tack sharp* but I'm beginning to wonder if that's just a fluke. I can't get a constant result from this lens in practical use. I've come to the realization that we got what we paid for. Sure it's a great lens for the price, but what good is a lens if it won't take a picture as seen in the viewfinder?
The first time I used this lens, I took a series of about 50 shots and I think around 5 looked like they were crisp.. and that's being generous.
I sort of agree with you regarding the focussing issue , but i have to say that the majority of shots i took yesterday were very sharp were ever it decided to focus , my problem was underexposing even in auto mode which i turned too because of bad exposing in other modes .

[mr.photoguy]

I sort of agree with you regarding the focussing issue , but i have to say that the majority of shots i took yesterday were very sharp were ever it decided to focus , my problem was underexposing even in auto mode which i turned too because of bad exposing in other modes .
Don't be scared to use your exposure compensation. I learned this yesterday, when in manhattan after reviewing the images, and reshooting with an extra stop of compensation added.
Then when I get home, I make shadow/highlight a part of my post processing..(learned that two days ago..) ..

All of this is learned as a result of doing the Photo A Day on Pbase, which lead to me meeting someone who taught me this.

[RAitch]

It's what I have been saying from the get go..

at 1.8 the DOF, and Area Of Focus is so shallow, it is way better to just Manual Focus.


Did you not read the rest of the thread? Yes, in THIS case manual focus worked better. However, in my previous samples, Manual focus turned out to be WAY worse then AF.

There just doesn't seem to be any consistency... and it doesn't seem like you can learn all the 'rules' of this lens in order to get a crisp focus wherever you want it. The results truly seem random.

[mr.photoguy]

yeah I would say shoot with it a bit more.
I don't shoot at 1.8 though... Rarely ever.
Mostly 2.8, and above, because that's when the lens starts to get sharp.

[RAitch]

yeah I would say shoot with it a bit more.
I don't shoot at 1.8 though... Rarely ever.
Mostly 2.8, and above, because that's when the lens starts to get sharp.

... and from my ruler experiment, it seems that's the threshold where the focus point is still inside the DOF... or at least you seem to get what you're looking at with MF.

I'll be shooting more, that's for sure.

[Dante King]

This pic of my daughter and her friend was taken last night with 300D , 50mm 1.8 , F2.2, 1/60 . Focus should of been on my daughter , the girl on the left , ....

Looks to me like the AF poit hit the ballon string. Looks as well as if that string is in the same focal plane as the other girl.

I would wager that the AF targeted that String as the Focus Point and ala the results posted.

RAitch,
You might want to go to a camera store with a fifty in stock and snap a few pics and then take them home and compare. If it is different, you probably got a "bad" lens. Maybe not a perfect solution, but it would be a decient test.

[Skip Souza]

Looks to me like the AF poit hit the ballon string. Looks as well as if that string is in the same focal plane as the other girl.

I would wager that the AF targeted that String as the Focus Point and ala the results posted.



By Jove, Dante, I think you've got it!!!!
The machine cannot lie, however, if not properly asked it will frequently misunderstand the question.

[RAitch]

I'll have to go out of town for a store that has a stock 50. Mine was a "special order" that took a couple weeks to get in.
Unless there's somebody else in the Sarnia Ontario area that has a 50 and is willing to experiment.

On ANOTHER side note, I took some outside pictures with the 50 from a distance and it had some nice results. I don't know if they were great, but not terrible. Of course, the apature probably wasn't 1.8... and I wasn't shooting from 3 feet away... or in a dimly lit place.

[RAitch]

Latest experiment... inconclusive.
I set my tripod up and twisted the diopter adjuster all the way counter clockwise (-).
From there, I tried to manually focus the image (about 2 or 3 feet away) on a stuffed animal's eyes.
The first 5 positions were difficult (image did not appear to be focussed) but the rest seemed to be easy to set.

So, I tried to manually focus the shot the best I could changing the focus from shallow to deep and back again... over and over again. Then I took the shot with a remote trigger. Spin the diopter 1 click to the positive (clockwise) and start over.

The results I got didn't seem to trend. I was expecting to see an area where the focussing was best but the results seem random (9 and 11 are sharp but 10 is blurry).
http://images.fotopic.net/?iid=y8syxl&outx=340&quality=70&original=1&noresize=1&nostamp=1

I understand that the DOF is extremely narrow... and now fully admit that while the 50mm lens is nice (because it's cheap), it is near impossible to get any clear images at 1.8 up close... and still hard from back a bit. Results definitely appear to be random. Normal portrait shots seem to have closer to normal results... but it's still difficult to pull it off consistently.

For those who recommend this lens for indoor photography because it has 1.8 and a flash is not required... I'd ask to rethink that. Get the lens because it's cheap... but anything under f3 is touchy... EVEN with a tripod. You'll still need some descent light to get nice results.

So far I'm happy with normal portraits from farther back (over 5 feet) and outdoor shots. I've given up trying to use this thing for closeups to fill the frame with a subject (baby's head).

[tim]

I'm going to confirm RAitch's findings: AF on the 50mm F1.8 doesn't work as expected at large apertures. If something looks in focus in my viewfinder, the photo that comes out is different. I've just had my lens calibrated by Canon, so I know that's not the issue. I think using focus points other than the centre point makes things worse.

Has anyone done this test using the 50mm F1.4? Or does anyone have both lenses who can do these tests? My other lenses don't have this problem (see list below).

My thread is here (http://photography-on-the.net/forum/showthread.php?p=518294), but maybe we should just stay on this thread for discussion of this problem.

[RAitch]

What I can't believe is that NOBODY has found this problem before I did. Everybody has been raving about the lens to the point where I went out and bought one.

Sure, the lens is cheap (SWEET!!) and it can get some sharp, in focus images. That's not what I'm complaining about (not really complaining... just trying to resolve). I've found that I can't take a consistant picture at 1.8 up close... that's all.

I find it hard to believe that with all the recommendations to use this lens because it's "good in low light" and all the recommendations to get the 1.4 (just because it can open wider - not because of USM) that nobody tried to shoot up close at 1.8. I say this because I haven't found a post anywhere that mentions this problem. If they did shoot up close at 1.8, why the heck hasn't somebody reported this issue or mentioned it? ("great lens for the price. Get one. Just be careful wide open up close.")
It seems that people are just parroting what they've read elsewhere. That's a dissapointment.

Now, at the same time, I've read a lot of replies to these problems that say "I have no problem getting a sharp image... look." While their posts are in fact in focus and sharp... I have a hard time believing that EVERY image they take with this lens will be sharp and in focus. At first I was just blaming myself for all the mis-focussed shots... but then came to realize that it couldn't be me. Also, it seems to perform better when used farther from the subject. Maybe the people that don't "have" this issue are just not getting as close as I require. I like to get in close and personal... especially when I'm trying to fill a frame with my son's face.

Tim, I'm thankful that someone else is actually admitting that there COULD be a problem here. If it turns out to be something else, then I apologise for my rant.

[cfcRebel]

I apologize ahead if you already covered/answered the following idea in your earlier posts.

I think at this point, I will go for Dante's suggestion, i.e. try another 50mm f1.8 on your XT(either borrow one from a friend or a store. i know, they have to special order).
Keep in mind, the minimum distance between your camera and the subject is 1.5ft(0.45m) as written on the 50mm lens. Good luck on your attempts.

[laatikko]

What was available light like when you did the tests?

My 50mm/1.8 shots were frequently off-focus when shooting in bad lightining conditions. Back in the January I took several hundred pictures of my kids and many had focusing problems. Now, with available daylight, I have no focusing problems with the 50mm/1.8, and I use apertures 2.0, 2.2, 2.5 and 2.8. Around two hundred photos of my kids, and all in focus (but kids moving...)

[O/confusion]

I'm going to confirm RAitch's findings: AF on the 50mm F1.8 doesn't work as expected at large apertures. If something looks in focus in my viewfinder, the photo that comes out is different. I've just had my lens calibrated by Canon, so I know that's not the issue. I think using focus points other than the centre point makes things worse.

Has anyone done this test using the 50mm F1.4? Or does anyone have both lenses who can do these tests? My other lenses don't have this problem (see list below).


Started to get nervous after reading this, so I just tried a casual test of my 50 f1.4, shooting a steel ruler at an angle on my dining table using light from a standard 60W tungsten bulb in an overhead pendant lamp in an otherwise dimly-lit room. Took some shots at 400 ISO, f1.4, 1/125s, manual exposure, one shot autofocus mode, evaluative metering, hand held at something close to the minimum focussing distance for the lens. Set lens switch to AF position, autofocussed using the centre point on the 6" mark--and the shot came out perfectly crisp and clear with about 1/2" of DOF in front, and a little less to the rear. Breathed large sigh of relief.

Sorry you're having such a hard time, RAitch. I don't recall if you posted the focus mode you've been using--has it made any difference as you shift between settings? (Apologies if you've already covered this.)

regards,
Terry

[RAitch]

I have covered that... but 4 pages is a lot to go through.
I tried all modes. I had some interesting results with AF on some stuffed animals. After focussing at infinity and using AF, I got different results than initially forward focussing and even after only using MF. I also got different results after moving back to about 6 feet (compared to 3 feet). In one test, AF was the favourite while the other test showed MF being the winner.

I've had poor results with both AF and MF. My MAIN concern is with MF. Using a tripod, release cable, and a stationary object... I MF on a particular point which looks crystal clear in the display. For example, using a stuffed animal, the eyes will be in perfect clarity while the ears are noticable blurry as well as the nose. Because I can see this clearly in the viewfinder, I would expect similar results in the final image. Results vary. Sometimes the nose is in focus, sometimes the ears (when I say "in focus" I probably mean crisp, in the DOF and in focus), and sometimes I can't make out what's in focus.

For almost all of my tests, I was using indirect sunlight through a bow window. At ISO 100, my shutter speeds were somewhere around 1/60 (remember, using a tripod, release, and stationary object). I even repeated some tests using ISO 800 to help boost the speed (thinking that might be a problem).

I just bought a 500W work light last night. Perhaps I should repeat some tests and post the results in a WELL lit environment. (by no means am I implying my original tests were in poor light).

I originally asked the question about light (without a real response from what I can remember) but can't see how that can be the issue when using a tripod, release, and stationary object. I would expect my DOF and focal point not to change even if my exposure time was over 1s.

[tim]

Tim, I'm thankful that someone else is actually admitting that there COULD be a problem here. If it turns out to be something else, then I apologise for my rant.

It's not just you and me, someone else said they'd had it too. Maybe it's an isolated issue, maybe it's a design issue.

What was available light like when you did the tests?

It's not that - my Tamron F2.8 worked perfectly, and the 1.8 should be better because of its wider maximum aperture.

[raylks]

Seems that the resulting focusing point is so different from what we see in the viewfinder. I suggest testing it by shooting on a scale with a tripod. And don't reframe your subject after you have half press the shutter release.

[tim]

I suggest testing it by shooting on a scale with a tripod. And don't reframe your subject after you have half press the shutter release.

It's pretty hard to reframe once you've put the camera on a tripod, but yes, that's a good tip for newbies.

[RAitch]

Seems that the resulting focusing point is so different from what we see in the viewfinder. I suggest testing it by shooting on a scale with a tripod. And don't reframe your subject after you have half press the shutter release.

That was the case in all of my tests. In fact, for most of them I enabled CF4-1 so half shutter didn't impact focus.... and even had the lens on MF.

Very good tip though as reframing would be devistating at such small DOF settings. That's why it's best to MF instead, so you don't have to recompose... but that's not working well.

I was tied up (not literally) last night. I'll do some more tests and post them ASAP.

Thanks guys!!

[RAitch]

I did some more tests as the sun was setting last night. It took me until about half way through to realize that the page was slightly off center. I didn't think to use the AF points to center the page (duh).

Anyway, when I started the sun was bright from the left. It gradually got darker and brought my shutter speed from 1/1600 down to 1/60. After that, all my auto focus tests were at 1/60.
As you should see, from the brief test, it appears that available light doesn't have a strong influence on MF. I would guess it would impact AF... but if it can function faster than 1/60 I wouldn't expect a problem.

Again, I used a tripod and a release cable. The test page (thanks Tim) was on a flat coffee table and the camera was pointed at roughly (eyeballed) 45deg down.

For the Autofocus test, I disabled custom function 4 so my release cable could trigger AF. Then I either pre focussed manually to the front or to the back... engaged auto focus then took the shot.

MF - http://images.fotopic.net/?iid=y8jhjw&noresize=1
AF - http://images.fotopic.net/?iid=y8jhjv&noresize=1

All of my MF shots were considerably front focussing. It seemed that AF worked best when starting back focussed (manually setting close to infinity). That's probably so when it gets an "approximate" lock, it'll be on the far side of the tollerance... which would be "closer" to correct.
It's hard to come to a definitive conclusion based on these results though. All I know is ALL of the shots are off. I didn't have ONE in crisp focus at the right point.

Oh, my focus point in the image was just to the left of "Focus here" and that's what I was trying to get in crisp focus. Silly me had the page off center for the first shots... but as you can see, it's WAY off anyway.

[300Dplus]

........ it is near impossible to get any clear images at 1.8 up close... and still hard from back a bit.......but anything under f3 is touchy...

It happens the same with my nifty. I did some tests - not as many as you did - and the results, as you can see in the pics, show the same problem.

Pic 1 is at f1.8 - 1/60 and pic 2 is at f2.8 - 1/160. Both in AF and taken with a tripod and using the 10 sec delay. MF gave me worst results. Used different light conditions and had same results.

I haven't check for inconsitency, but the fact is (with my lens) that anything under f2.8 is not sharp.

Thanks for bringing this up...

Tom

[RAitch]

Well the 1.8 isn't very sharp but the "Focus here" text looks pretty good.
At least yours is focussing at the approximate correct location. I'd take your results over mine. The second shot is extremely sharp.

It looks like your AF is right on. Either that, or the 50 doesn't work well with the Rebel XT and is fine with the other cameras.

To be honest, I'd be happy with a little unsharp images at 1.8. The truth is, mine are farely sharp... just not at the right focal point.

Keep the test shots coming.

[pradeep1]

I had a similar problem to this on my dRebel XT. I could not get crisp focus with my 50 f/1.8 using the ruler test, etc. I turned my camera into Canon and they recalibrated the focus and I got it back. I then tried various tests with multiple lenses and all of them were tack sharp, even on the slanted ruler, and newspaper tests, but the 50 1.8 was not sharp. Using a tripod, set at f/1.8 and shooting newspaper that was taped to a wall flat and shot in bright sunlight, the lens could not focus on the paper. I called Canon and the tech service rep said that most likely my 50 1.8 has a problem, since the body was recalibrated and I was not having a problem with any other lens. So do consider this....it may be the 50 f/1.8 that is at fault. You can't expect perfection for a $80 lens, right? ;)

[RAitch]

True, and I'm in the same boat... what do you expect for such a cheap lens.
What I'm kind of confused or ticked about is that NOBODY has reported this OBVIOUS problem. Because of all the good reviews (and lack of bad ones) I just wasted $150CAD. I'm not happy with the nifty fifty at all.

So my question now is (realizing that this lens is substandard) why does everybody rave about this lens when there are such problems with it? Are 'we' just regurgitating what we heard and trust that it's a great lens? For what I want to use it for, it's totally useless. Is it just a problem with the Rebel XT? I can't see how it can be user error like most people claim. For the people that claim the lens is "tack sharp" and post sample pictures, were those samples 1 picture from 100 blurry or out of focus pictures? If so, how can you claim the lens is tack sharp when it's a crap shoot to get the picture? The only way I get sharp close-up pictures is if I guess right and manually focus to a different area... which seems to change based on distance. Sure, it seems to work well for distant portraits outside in sunlight, but everything else is crap. Explain to me why if it's not just a fault of being a "cheap" lens.

For sanity sake I posted this thread to get confirmation from other people hoping that all these other people that reviewed the lens never tried up close photography at 1.8. It seemed until I brought it up that nobody had ANY issues with this lens (past the cosmetic plastic and non USM).

Sorry for the rant... as you can tell I'm frustrated with this thing.