camera or lens problem (DRebel or 50mm 1.8)?

[shooter76]

Hey all....my first post!! Got a ? I just bought the 50 1.8 since I have heard such good reviews for the cost of this thing. This is the problem. When I shoot up close and with the aperture set to 1.8 my images are out of focus. It is focusing in front of the subject by about 5mm. Now this doesnt sound like alot but when your dof is this small it doesnt take much to throw it out. 3/4 of the shots turn out this way with this lens and the settings I described (very close & 1.8-2.8). So hoping it was the lens I went and bought another 50 1.8......same problem. I have 3 other lenses that I have tested and they seem to focus fine with my focal point right in the middle of my dof. 18-55 kit, 28-105 3.5, 80-200. I was using a test I found on this site where center af on a vertical surface is used with a ruler running semi horizontally (40degrees going up) next to the vertical surface to see the affects of the dof vs. where the vertical and horizontal planes meet. Sorry for long post. Someone help please. What is wrong here? Thanks in advance.

[RichardtheSane]

How close to the subject are you?

What does it do on manual focus :)

[drisley]

The minimum focusing distance for that lens is 1.5 feet.
Perhaps you are getting too close to the subject?

EDIT. Oh, now I read that you said it is focusing in front of the subject, so that should rule out the above.

I might have to do some testing myself.

PS. How close is "close" exactly?

[shooter76]

I am getting within an inch of as close as I can get and still lock focus. I did not try manual focus. Even if i move back a few inches it still will focus right to the outside edge of the dof. Actually I would say past the outside of the dof since it is focusing where it is not sharp. My kit lense can get in very close and focuses perfectly.....but then again my aperture on the kit lense is only 5.6 at 50mm and not 1.8. The reason why I even looked into this to begin with was because my shots were not very sharp with my 50 1.8 when shooting normal distances at large apertures.

[drisley]

So, is the 50F1.8 focusing BEYOND the subject?
Or is it focusing before the subject? If it's beyond, then you may be too close. The minimum focusing distance is 18 inches, while the kit lens has a minimum of only 11.8 inches.
That means you can get over 50% closer with the kit lens.

The 50F1.8, like most lenses, is softer wide open (but still much sharper than the kit lens even at it's widest F5.6 at 50mm), and begins to get nice and sharp at about F2.8. Then it REALLY gets sharp at F4.0.
Also, the DOF is so razor thin at F1.8, so when you take a picture of someome at normal distance, it's not unexpected to get say the eyes in focus, but the rest of the body blurry (depending on angle, etc).

18-55mm Kit Lens
http://www.mts.net/~lftbrain/rebel/18-55mm.jpg

50mm F1.8 II
http://www.mts.net/~lftbrain/rebel/50mm.jpg

[Yeager]

You posted your pics while I was typing this.

[shooter76]

It is not focusing beyond the subject....it is focusing before. My subject falls to the backside of the dof where it begins to get blurry. My 50 @ 1.8 is much blurrier than my kit lens at 5.6. It seems almost all of my pics taken with the 50mm are soft.....even with the second 50 lens I bought. I am beginning to think that my camera needs to be calibrated or something.

[cmM]

I haven't heard many people complaining about this lens... I have it and I never had any issues with it (or at least noticeable issues). It's sharp, even at f/1.8 There was a thread a little while ago about this lens not being very sharp at all at 1.8, but the conclusion was that there is nothing to be blamed except the very small DOF at this aperture.

But if it's really bad, you might wanna have your camera / lens checked.

[shooter76]

I did a little more testing......I moved back a little more and now it is all over the place. About 7 out of 10 are in the depth of field and about 2 out of those 7 are really sharp. The other 3 are unusable. I was taking shots from a tripod at about 3ft. I tried both lenses and they did the exact same thing. Max range of focal movement between exact shots was about 2 inches with average staying within 3/8 of an inch. One lens had 7 out of 10 usable shots the other had 6 out of 10. Is this acceptable and normal or should I be concerned. :(

[sssanti]

I have exactly the same problem described by shooter76 with the 50mm 1.8 using a rebel XT. When using the 50mm 1.8, the camera always focuses closer than where the focus point is. This problem is very clear at 1.8 at close range. Flat subjets like a newspaper parallel to the sensor are always out of focus. If the newspaper is at an angle, a portion of the page is focused, but the focused portion is clearly closer to the camera than the area under the focus point. This occurs at about 2 ft and also at 6-8 ft. When using the kit lense (18-55) the camera focuses precisely the area covered by the focus point. Due to the smaller aperture and greater DOF, the kit lense can only be easily tested at close distances.
Has anybody found a resolution to this problem?

[Mr. Clean]

Huh.......I shot a couple pics this weekend and they looked front focused with the 1.8, so I shot a couple lens boxes and the words looked front focused too. I shrugged it off as user error though....

[RuggerJoe]

Something to keep in mind is the auto focus sensor can extend out side of the box in the veiw screen. If there is something with greater contrast "in view" of the sensor, it will focus on that rather than what your are intending it to. Also at that depth of field moving ever so slightly can through it off, but that shouldn't be a problem if you were using a tripod.

[gcogger]

How good is the light where you are testing? I have seen numerous complaints (including my own ;) ) of erratic focus using this lens in poor light. Perhaps try some tests in bright sunlight?
In the end, that is why I got rid of mine. A fast lens that could not focus properly in low light is of little use to me :(

[shooter76]

nope....never fixed it.....as long as i dont shoot with a wide aperture it seems to be much better....not perfect but better. i dont take it much below 4.

[JunkieXL]

Hi,

I have the same problem with my 50 f1.8 II, it's front focusing 10mm. I also have to use a smaller aperture (4 or 5.6) to increase DOF and reduce out of focus effect.
I did the same test with my 28-135 and the focus is perfect. You can send your lens for calibration or live with this limitation :-(

Regards,

Diego

[sssanti]

Thanks for the input. I tested the EF 50mm II 1.8 indoors with different light conditions and it does not seem to make any difference. I also used the flash to assist with focusing and again it did not make any difference. I also tried using different focus points. The results are the same. The lens is pretty sharp even at 1.8 but not for the area I want in focus. It is front focusing very consistently. When focusing at close range the lens barrel has what I think is a significant play. Is some play normal for this lens?
Since the body works fine with the 18-55 I assume the lens is defective. I am trying to get a replacement. I'll report what I find with the second copy when I get it.

[marctwo]

I have the same problem. At first I thought it was an issue with my new 30D, then I realised it was the lens. Wide open this is apparently quite common. I have the Mk 1 version of the 50mm, I don't know if this makes any difference. Even at f2.8 I had rather inconsistant results (2 out of 10 shots well focussed). I guess I shall try shooting at f4 in better light instead or consider the f1.4 USM version instead.

[Mr. Clean]

huh - very interesting. I would set up a focus test, but what if I find it's front focusing? It's not worth the money to send it in, it's only 70 bucks! Plus, upping the aperture seems to defeat the use of the lens.

[sssanti]

I got a replacement EF 50 mm 1.8 lens. The replacement had the same front focusing problem as my original lense. I decided to send the body (Rebel XT) and the lens to Canon for repair. I got it back and the problem is still there. Focus is probably less reliable after the camera was adjusted to factory standards, however, the tendency to front focus at 1.8 is still there. This happens for all light conditions, as long as it is at full aperture. It can be seen with a focus chart and also taking actual photographs. Since the focus seems ok in the viewfinder, it is imposible to try to focus manually (I miss my old film camera in this regard).
I have read about this problem in this an other forums. It seems to affect many people. Some people discount it as operator error or blame it on the small DOF. Others recommend using the lens at 4 or higher.
By now I wonder if there is a single person being able to use this lense at 1.8 with a Rebel XT without focusing issues.
I decided to send the camera and lens again to Canon and I am waiting to get it back. If they are not able to fix it this time I think they should start giving refunds.

[theJingster]

i also have the 1.8 but never really noticed a problem with missed focus until recently. i was shooting in "ok" lighting so i upped the ISO to 400 and was getting shutter speeds of 1/1000 or faster but many of the shots came back slightly out of focus. i chalked it up to a slow shutter speed and moving subjects (people candids). now i'm thinking maybe it's missing focus, except that i never had a problem with it before last week...