new 70-200 backfocus @70mm, ok @200mm?

[summerwind4]

i just got the 70-200f/4L, and the lens backfocuses at 70mm, but seems to be ok at 200mm but with a hint of inaccuracy when AF'csing.
has this been a problem with the 70-200 f/4L's?

my first 70-200 i had and sold didn't do this as i recall on my D60.
the new one is being used on a 20D

[accord]

I just find that mine got the same problem.
I have shoot over 300 photos using this lens, never find a sharp one. I have tested the lens using focus chart, it works fine. Today, I test with real subjects, it was back focus on most of the shoots on my son and his toys.
I'll send the lens for fixing on the coming Monday. It is my first L!

[blue_max]

I find it works better if you ONLY select the centre focus point. When you have so many points on the 20d, the focus point can tend to grab the point of highest contrast if there is not much contrast in the centre.

You also need quite a high shutter speed and steady hand with such a relatively large lens. The depth of field is quite shallow at f4 if you are quite close to your subject (more likely at the 70mm end).

It may be just worth doing some controlled experiments with these issues in mind, before you send the lens away. It's a pain and if it is fine, you will feel very frustrated.

Try setting just the centre focus and see if it helps at all.

Fingers crossed.

Graham

[accord]

I have long in using center focus point, trying different shutter speeds.
There is no one single occasion sharp image!

[accord]

I got sharp images when shooting newspapers. In real shooting, I just cannot get one single sharp image from f/4 to f/8.

[summerwind4]

thx blue,
i know when i got into digital some 3 years back, i use to test my D60 with whatever lens i bought by shooting actual photos of stuff (no charts, rulers, newspapers.....lol) and could tell from the results if all was well.
well since then i've learned that yes, the center point is the only thing to use when first trying out a lens, and definately test by shooting in good light. second, i shot targets with high contrast.
at the long end, this lens is sharp, at the wide end it is sharp too, but it is focused at 1.5 feet behing the target.
to verify this i set the 17-85 back on the cam and shot the same targets, and every shot was focused on the target.
trust me, i tried various targets and apertures, and after going through 3 copies of the 24-70 did i learn just what FF or BF is all about.
now this morning i will go to the shop and try the other 70-200 they have.
i also had in this last week tried the 70-200f/2.8 IS, and it focused perfectly at both ends, but i don't need the speed or the weight.
i'll follow up for you all, but i am hearing more that the f/4 version on a 20D seems to have this problem..............of which if it's the same with the second copy, i'll send it in like accord said.

[blue_max]

Apologies for any incorrect assumptions. You are both experienced shooters. I have the 10d and doesn't suffer from the problems you describe.

Hope you find a resolution.

Graham

[summerwind4]

Apologies for any incorrect assumptions. You are both experienced shooters. I have the 10d and doesn't suffer from the problems you describe.

Hope you find a resolution.

Graham

you never need apologize to me.....i got a hide thick as a hog:lol: :lol:

the one thing i love about this site is the courteous way people answer others here with suggestions on what the problem may be.
other sites would have indicated a need for exchanging first, or "yes the 70-200 is a dog" type posts.

your input is what i prefer to see as it may uncover something i may be overlooking.
i have only myself to blame at this time because i once had a perfect working copy of this lens and sold it a while back to buy some new golf gear. shortly after that, Zoey came into my life..............

http://www.pbase.com/summerwind4/image/39541926

and i have found the need for a longer lens again.

[blue_max]

you never need apologize to me.....i got a hide thick as a hog:lol: :lol:

the one thing i love about this site is the corteous way people answer others here with suggestions on what the problem may be.
other sites would have indicated a need for exchanging first, or "yes the 70-200 is a dog" type posts.

your input is what i prefer to see as it may uncover something i may be overlooking.
i have only myself to blame at this time because i once had a perfect working copy of this lens and sold it a while back to buy some new gold gear. shortly after that, Zoey came into my life..............

http://www.pbase.com/summerwind4/image/39541926

and i have found the need for a longer lens again.

Ahhh! I think you might need the 70mm end most!

I wonder if it has something to do with the 20d then (it seemed to work for you with the d60 and on my 10d).

Nothing else springs to mind unfortunately apart from the close focus/less close focus switch. That couldn't have any bearing could it? – I know it shouldn't, but you never know.

Graham

[accord]

Oh yes, thanks for all your input.
I have just managed to get sharp picture out of indoor flash with the 20D+70-200 f/4L. I can't be happier. There is only one out of six got back focus.
I find this lens is the most difficult lens to use among 17-85, 27-75 2.8 Xi and 50 1.4.
So what is wrong with all my previous shoots?
Is the angle of light to the object matter?
How about use a hood? I'll try next time.
This lens is a keeper anyway, the sharpest among my lenses collection.

[summerwind4]

hey folks, i got the exchange this morning and the new one is dead on.........the serial numbers are only 500 apart so i thought for sure on the way home that the results would be the same. this one focuses exactly where it's pointed. looks to be a tad better than my very first 70-200 i sold a while back.
this sure made my weekend

[93octane]

what were your old serial and your new serial numbers??? Just wondering I'm getting mine in this Tuesday but I had to send in my 300D for repair because the hot shoe wasn't working properly so I'm not going to have a camera to test it out until the Rebel comes back. Just want to know if mine is going to close to the serial that yours had a problem with or close to the good copy.

[blue_max]

hey folks, i got the exchange this morning and the new one is dead on.........the serial numbers are only 500 apart so i thought for sure on the way home that the results would be the same. this one focuses exactly where it's pointed. looks to be a tad better than my very first 70-200 i sold a while back.
this sure made my weekend

You must be really pleased. When the lens is good, it is very, very good.

There are so many reports of 'bad' lenses, that you don't know what to believe. The trouble is, we want to believe it is operator error, or we all have a chance of picking a bad one. It really annoys me that there should be any such thing.

Enjoy it now.

Graham

[summerwind4]

You must be really pleased. When the lens is good, it is very, very good.

There are so many reports of 'bad' lenses, that you don't know what to believe. The trouble is, we want to believe it is operator error, or we all have a chance of picking a bad one. It really annoys me that there should be any such thing.

Enjoy it now.

Graham

bad reports are a given lately, especially since we pixel peep eh?
only other lens i had trouble with was the 24-70 and it really was a focusing error.
Canon needs to set one bench tolerance for all it's current bodies (as if that's possible) and then keep lens tolerances tighter.
hard to believe a lens just 500 numbers away could be calibrated better than the other................or do we chalk it up to Sake?:lol:

[summerwind4]

what were your old serial and your new serial numbers??? Just wondering I'm getting mine in this Tuesday but I had to send in my 300D for repair because the hot shoe wasn't working properly so I'm not going to have a camera to test it out until the Rebel comes back. Just want to know if mine is going to close to the serial that yours had a problem with or close to the good copy.

1st lens was #2100257443
2nd lens is #2100257946

[93octane]

Thanks for the serials... I'll have to wait till Tuesday to get the lens and then wait till my camera comes back. Kinda of disapointed its true it shouldn't be I HOPE I get a good copy. It should be that all or at least 95% of all lenses should be good and a bad here and there. I bought this lens because its 1. Canon 2. L glass 3. everyone raves about it. I figured because of 1 and 2 all of these lenses were good copies. Now I'm hoping I don't get a bad copy. Same thing with the Tamron 28-75 I need to order one but it goes to the same thing I HOPE I get a good copy. I don't have any local store here I can go try and return if its bad. I need to order online.

[Bob_A]

Oh yes, thanks for all your input.
I have just managed to get sharp picture out of indoor flash with the 20D+70-200 f/4L. I can't be happier. There is only one out of six got back focus.
I find this lens is the most difficult lens to use among 17-85, 27-75 2.8 Xi and 50 1.4.
So what is wrong with all my previous shoots?
Is the angle of light to the object matter?
How about use a hood? I'll try next time.
This lens is a keeper anyway, the sharpest among my lenses collection.

Do you get the back-focus problem at all f-stops or just at f-8? The focus for my copy of the 70-200 f4L is bang on at f4 for 70 and 200mm, but it has a some back-focus at f8 (at both 70 and 200mm). At f8 the focus is nipping the edge of the DOF.

At 70mm the AF for my 24-70 2.8L is perfectly in the center of the DOF at both f2.8 and f8.

[ed rader]

you better get a macro for that one too, eh :lol: ?

what a cutie!

ed rader

[accord]

Bob_A:
The focus of my 70-200 f/L is intermittent. Several shoots of the same object, focusing each time can have different outcomes.
That is why I want to find a way to make it consistence.

[Bob_A]

Bob_A:
The focus of my 70-200 f/L is intermittent. Several shoots of the same object, focusing each time can have different outcomes.
That is why I want to find a way to make it consistence.

Is the focus always inside the DOF, or is it sometimes waaaay off? Also, do you get the same result with the AF distance switch in either position?

Maybe something is causing the lens to jump a bit when AF is locked. I seem to recall reading threads a few months ago from someone on the forum having a similar issue.

[willg]

when you guys say you are having focus troubles....is it all the time or just on select shots...my 70-200 f4 is dead on sometimes but a lot of times its just slightly out of focus (high shutter speeds of course)

[accord]

Willg,
My 70-200 f/4 is similiar, it is dead on when shoot newspaper, the famous focus chart. When dealing with real life photos, I cannot find one which can be identified as dead on. They all appear slightly soft.
This is one example of 100% crop:

[accord]

Here is the original picture, 200 mm, f/4 and 1/500s:

[Johnny V]

I had same backfocus problem with my 70-200f4 L, Sent to Canon and now it front focuses at 70mm with auto-focus. At 200mm it's dead on with auto-focus.

With camera on a tripod ...at 70mm I manually focus on an object at 30 feet and it is dead sharp. But if I turn on the auto-focus button and touch shutter button I can see the lens refocus about 6 inches foward.

Will have to send lens back to Canon.

[tim]

Accord - that pic of the guy on the bike has poor contrast, did you use the hood? It looks a little back-focused to me.

I haven't taken many photos with my 2.8 IS yet, but every photo's been very sharp, so long as I haven't done anything stupid (move too much, shutter speed too slow, etc).

[Bob_A]

Unless this guy has incredible balance, I assume he was moving on that bike :) I realize that you took the image at 1/500s, but at f4 the depth of field isn't great ... so if he were 50 ft away and moved only 1.5 feet closer to you after gaining focus you would get this result.

Were you using A1 Servo AF?

[accord]

Oh, you have very critical minds.
I had not used a hood on this picture. Next time, I will for better contast, thank tim.
I had not use A1 Servo AF for this shoot. Let me assume he was moving at a speed of 5 km/hr (1.3 m/s), he was moving slowly. I had triggered the shoot just after focus with the "*" button". Let me assumed it had 0.1 s delay. Yes, it might have 0.13 m (about 0.5 feet) error. Thank you Bob.

[Bob_A]

Oh, you have very critical minds.
I had not used a hood on this picture. Next time, I will for better contast, thank tim.
I had not use A1 Servo AF for this shoot. Let me assume he was moving at a speed of 5 km/hr (1.3 m/s), he was moving slowly. I had triggered the shoot just after focus with the "*" button". Let me assumed it had 0.1 s delay. Yes, it might have 0.13 m (about 0.5 feet) error. Thank you Bob.

He's gotta eat his Wheaties so he can get that bike moving faster! :lol:

[blue_max]

Thinking laterally about this back focussing issue. Couldn't you just focus and take a step backwards – perfect! :lol:

Graham

[accord]

Thinking laterally about this back focussing issue. Couldn't you just focus and take a step backwards – perfect!
Yes, I'll try next time. Practice is the king! Otherwise I may get shaky image instead of backfocus.<img>

[blue_max]

Dang, knew that lateral thinking thing was too clever for me, you obviously need to take a step forward. Sorry to all those that have been out practising the 'steppin' sheep' technique.

[accord]

For those moving object, there are lot of technique I can and will learn.

How about this one, f/8, 1/4000 sec. Everything stand still!
Head and full.

[Bob_A]

Here is a bee shot that I took yesterday messing around with my 70-200 f4L @ 200mm, 1/1000s and f5.6 (ISO 800). I used Neat Image to get rid of some of the noise and applied some USM.

I wouldn't classify the 70-200 as a replacement for a macro lens, but I was curious to see if I could get an acceptable image. Considering the bees were zipping around all over the place I was surprised that this came out as well as it did. Also, even though the 4L isn't all that big, it is a bit more of a challenge to keep steady than a standard zoom, so I can see I need a lot more practice.

[Wavy C]

I was trying out a 70-200mm today (on a 20D) and found this exact same problem!

Backfocus at 70mm, not every time but about one out of five shots. Really annoying! Seems to focus correctly from about 100mm upwards. I was mostly using single off-center focus points, and some with the centre. The f-stop was 5.6. When it's sharp this lens seems very sharp, when it's out of focus.... useless!

The backfocus thing really took me by surprise on some shots where I had spent ages making sure the focus point was in the exact right place, with plenty of contrast etc.

Has anyone else noticed this behaviour?

[Keiffer]

Oh geez you guys are scaring me. I'm in the process of buying a 70-200 F4 from a fellow forum member. He didn't mention anything about a focus problem and I'm sure if it did have a focus problem he would tell me. But do these lenses get out of focus over time or is this an isolated incedent? I hope so for my sake LOL

[summerwind4]

Oh geez you guys are scaring me. I'm in the process of buying a 70-200 F4 from a fellow forum member. He didn't mention anything about a focus problem and I'm sure if it did have a focus problem he would tell me. But do these lenses get out of focus over time or is this an isolated incedent? I hope so for my sake LOL

don't worry about it..........it's not a big deal if you have the problem and most all of them don't.
after finally verifying that mine did have a problem i simply sent it in and it was rectified and now is the best thing since the invention of the DSLR.

[JMAS]

It's true.
It backfocuses. :rolleyes::rolleyes:


http://images.fotopic.net/?iid=y8hw95&outx=0&quality=70&noresize=1

:p:p
J/k It's a great lens all the way. No issues here.
http://images.fotopic.net/?iid=y8hfbc&outx=0&quality=70&noresize=1

[Keiffer]

Thanks I needed to hear that and also just got mine today and it looks good, No prob here, I think LOL I will run the gamut with it tommorrow though.
And Bob...You slay me LOL quote: unless he has great balance he must be moving on the bike LOL
After I take some shots tommorrow I'll post them.. Hopefully in the right forum compared to the mistake today by accidently posting my Joining the "L" lens group in Marketplace LOLdon't worry about it..........it's not a big deal if you have the problem and most all of them don't.
after finally verifying that mine did have a problem i simply sent it in and it was rectified and now is the best thing since the invention of the DSLR.

[eggrollboy]

Can't wait to open mine next Monday. Apparently it was shipped to my work address and I'm home on the weekend!

[Keiffer]

Are you crazy man! Go to work and get it! LOL I look forward to seeing some shots.Can't wait to open mine next Monday. Apparently it was shipped to my work address and I'm home on the weekend!

[eggrollboy]

Hmmm, I don't post much at all and I finally realized why...

I posted this in 2005 and I'm just replying to it now!

Well, better late than never!

My fave shot using this lens:
http://farm1.static.flickr.com/77/170120433_85fe8fcaf0.jpg

http://farm1.static.flickr.com/61/170120236_65cfcefa1f.jpg

Cesar Millan!
http://farm1.static.flickr.com/65/170089727_8a5710db44.jpg