Canon 40D - Autofocus Problem

[FM1]

Hi guys. Im having some problems with my 40D - there seems to be an issue with my autofocus (I think). For some reason it does not focus on the central point in the 'red eye' but rather around it. Only on a very few occassions it will actually focus on the central point. So now all the photos I have taken on my holidays have turned out extremely soft.

I have a suspicion that it is when I shoot in manual mode as the only two photos that shot in auto turned out to be perfectly in focus. I thought it may have been shutter speed (1/500) but I increased to 1/800 but even then I have the same issues. The unusual thing is that when Im looking through the viewfinder and using autofocus, the subject looks perfectly in focus. Something goes wrong when I take the photo.

Im using a Tamron 17-50mm f/2.8 lens. I have some example photos below. The second photo was taken within minutes of the first. Both in full manual. Just cheking the exif data on the photo, there is no mention of the focal length or exposure bias on the soft image.

Soft

Sharp

Any help is greatly appreciated. Thanks.

 

[Deleted member 3428]

The first shot is shot at f2.8 and the 2nd at f7, not knowing the lens but going by most others you might find the lens is always slightly soft at f2.8 and needs a stop or 2 down too get the best out of it.

 

[Badger UK]

Why are you using manual? Do you mean manual focus or camera settings?

 

[paleblue]

It's your lens. At f2.8 it will be softer than a smaller aperture. I found the same problem on my sigma 17-70 at f2.8

 

[DizMatt]

I would check out the f2.8
I have exactly the same kit
the 17-50 focuses very close so that's not the problem.

take your lens, focus it across the street, try different Av numbers and check out the sharpess of some writing across the road.
there is quite a difference in the images.

 

[POAH]

probably just the light and miss focusing. your DOF is not going to be big at f2.8 and you are in shadow there. AF works on contrast so your camera will be struggling to get good AF on the guys face

 

[andrewc]

are you selecting the focus point or is it guessing which one to use?

 

[FM1]

The first shot is shot at f2.8 and the 2nd at f7, not knowing the lens but going by most others you might find the lens is always slightly soft at f2.8 and needs a stop or 2 down too get the best out of it.

It's your lens. At f2.8 it will be softer than a smaller aperture. I found the same problem on my sigma 17-70 at f2.8

I would check out the f2.8
I have exactly the same kit
the 17-50 focuses very close so that's not the problem.

take your lens, focus it across the street, try different Av numbers and check out the sharpess of some writing across the road.
there is quite a difference in the images.

So is this an inherent flaw with the Tamron lens or is that the case with all lenses (even Canon L series ones)? For me its just really annoying to pay for an f/2.8 lens and not be able to use it at max aperture because the image turns out soft.

Is there a way to remedy that or is it just something I have to live with?

Why are you using manual? Do you mean manual focus or camera settings?

Manual camera settings and full auto focus.

probably just the light and miss focusing. your DOF is not going to be big at f2.8 and you are in shadow there. AF works on contrast so your camera will be struggling to get good AF on the guys face

Its the same issue when I shoot in full daylight too.

In a situation like that (shadowy environment and shooting at f/2.8) is manual focus recommended?

are you selecting the focus point or is it guessing which one to use?

Its guessing which one to use. Im assuming the central point in the red eye.

Is there a way to actually configure or calibrate that?

 

[packham]

If you let the camera choose focus points for you it may not land on the area you want to be in focus. To manually choose and fix a focus point, consult your camera's manual (if you're using Canon, press one the buttons near your thumb).

Edit: Now that I see you are using Canon 40D from the Exif. In that case, press rightmost button (next to *). You can also custom funtioned it so that focus point can be conveniently chosen using the joystick near your thumb. I did this on my camera, very convenient

 

[paleblue]

I may be wrong, but there is no way to remedy the softness at f2.8 other than adjusting the sharpness level in camera and/or in photoshop. If you really want a good sharp fast lens for low light, i'd recommend a prime; the cheap and cheerful 50mm 1.8 may be a good addition to your camera bag

 

[Cobra]

By keeping all the "red focus points" selected the camera will "choose" which
one to use
top right button ( rear) to select focus points and turn the wheel
this will scroll through each point in turn stop when you reach the desired
one ( in your case centre)

edit EXIF says 50mm and 0 bias

 

[andrewc]

I think you need to read the manual on how to select different focus points.

I have mine set up with the joystick - push in to select central, joystick to select others, top right hand button to select all and put it back into auto mode.

The camera tries hard but it can't always know which part of the image to focus for, and DOF at f2.8 close up will be thin.

 

[Cobra]

I have mine set up with the joystick - push in to select central, joystick to select others, top right hand button to select all and put it back into auto mode.

I left mine "as is" as above ( default) and find it easier thats the trouble when there
are too many options


Oh and a quick edit does bring out the subject "better"
( shadows / highlights and a tad USM )

 

[HoppyUK]

The first photo is just out of focus. Sharp focus is around the ears, in line with the chest, and there's not enough depth of field at f/2.8 to pull it all sharp.

Just sharpen up your technique

 

[FM1]

If you let the camera choose focus points for you it may not land on the area you want to be in focus. To manually choose and fix a focus point, consult your camera's manual (if you're using Canon, press one the buttons near your thumb).

Edit: Now that I see you are using Canon 40D from the Exif. In that case, press rightmost button (next to *). You can also custom funtioned it so that focus point can be conveniently chosen using the joystick near your thumb. I did this on my camera, very convenient

Thanks for that. Ill give that a shot and see if that remedies the situation.

I may be wrong, but there is no way to remedy the softness at f2.8 other than adjusting the sharpness level in camera and/or in photoshop. If you really want a good sharp fast lens for low light, i'd recommend a prime; the cheap and cheerful 50mm 1.8 may be a good addition to your camera bag

I have the nifty fifty but its just such a hassle to swap lenses over I just usually carry the 17-50 f/2.8 on holidays.

By keeping all the "red focus points" selected the camera will "choose" which
one to use
top right button ( rear) to select focus points and turn the wheel
this will scroll through each point in turn stop when you reach the desired
one ( in your case centre)

edit EXIF says 50mm and 0 bias

Thanks for the tip. I will re-adjust the focus settings and see how I go.

So is it an issue if its shot at 50mm and 0 bias? I have been told that shooting at an increased focal length can cause the image to soften but I havent seen any backing evidence.

I think you need to read the manual on how to select different focus points.

I have mine set up with the joystick - push in to select central, joystick to select others, top right hand button to select all and put it back into auto mode.

The camera tries hard but it can't always know which part of the image to focus for, and DOF at f2.8 close up will be thin.

Yep, the camera auto focus setting adjustments definitely sounds like the right way to go.

 

[FM1]

The first photo is just out of focus. Sharp focus is around the ears, in line with the chest, and there's not enough depth of field at f/2.8 to pull it all sharp.

Just sharpen up your technique

I had a feeling my technique may have been it. Any suggestions on improving it?

 

[packham]

I had a feeling my technique may have been it. Any suggestions on improving it?

Sometimes when you confirm focus, release the finger and confirm focus again, the focus ring may move a bit. That means the first (or second) focus may not be exact. To make sure the focus confirmation is exact and stable I always confirm focus a few times until the focus ring stays fixed even after reconfirmation. That should (hopefully) give me a perfectly in-focus picture. Just my little personal technique

 

[Cobra]

So is it an issue if its shot at 50mm and 0 bias? I have been told that shooting at an increased focal length can cause the image to soften but I havent seen any backing evidence.

The soft focus at the "long end" tends to be a "problem"
with longer lenses than that.
My 24-105 for example I don't notice
any difference
the 70-200 with a 2x tc tends to get soft at around 350mm
I don't however have any experience with tamron 17-50
maybe someone else will be able to answer that better than I

 

[tdodd]

How sharp is the guy's hair - the fringe in particular? It is tough to tell with the small image you posted. I'm thinking the camera did focus correctly but the shaded face means there is so little contrast that it looks to be soft/OOF as there are simply no well defined edges in the face.

A 100% crop of the hairline and a 100% crop of the eyes and teeth would help, or if you can post the original unedited file somewhere, with all EXIF intact, then it might be possible to provide more answers. At the moment I am not sure there is anything wrong with the kit, just the expectations.

 

[HoppyUK]

I had a feeling my technique may have been it. Any suggestions on improving it?

I'm as reasonably certain as I can be that this is a focus problem. This is usually caused by using the lock focus-compose-shoot method, which I always use myself, but there is always the danger that either you or the subject moves between the first half-press of the shutter which locks the focus and final release.

For me, it's still the best method, but with subjects like this I am constantly focusing and refocusing, because people move slightly all the time. It is clear from the image that there is only an inch or two of depth of field, and that aspect works well, but you have to nail the focus and I guess a certain failure rate is inevitable if you shoot at f/2.8.

Looking at the image again, it looks like the fringe is sharp, and the emblem on the shirt is too, but the eyes and the nose have drifted out. You just have take more care, and double-check focus frequently.

The image is also not helped by being very low contrast, and I'm sure a bit of tweaking in post processing would help quite a bit. The other thing that might have worked well is to give it a tiny burst of fill-in flash - not so much that he looks like a cardboard cut-out, but just a tad to lift the shadows and put a sparkle in the eye.

Try it sometime - it's real easy with the camera on Av, which automatically balances the flash with the background. If the flash is too bright, which it often is, turn it down with minus flash compensation. Of course, you have to keep the shutter speed within the x-sync range and that's not always easy if you want to shoot at f/2.8 in bright sun, but it's an option worth considering.