Canon 50mm 1.4 focus issues

I have a 50mm 1.4 for more than a year, but some focus issues have been happening more and more recently.

I have read a lot about focus issues on this lens in particular, but I wonder if this is something about the lens or about what I'm doing.

Any tips? I feel do frustrated when this sort of thing happens and it has been quite frequent lately.

Thank you!

Focusing at f/1.4 can be a real challenge.

The question is, HOW do you focus now? What procedure do you use? The more details you provide, the better we can deduce what your problem is (or if it is an equipment problem).

- What camera body do you use?

- What mode do you shoot in?

- What AF mode do you use?

- Do you select a focus point, or do you let the camera choose for you?

- Do you put the focus point on a high-contrast edge? Or do you just point the camera in the general direction of what you are trying to photograph?

- Do you focus first, then shoot?  Or do you just press the button?

Sorry if these questions seem basic, but I have no idea what you know or don't know about focusing.

Here is a three-part tutorial that is worth watching (several times, if necessary): http://www.youtube.com/watch?v=iAx86nblZ2g&feature=relmfu

Do you understand cropping and DOF (or the lack of it)?

ClaudiaC wrote:

Hello Bill! Thank you for all those questions, I do understand the need of those and I am sorry for not providing more information. So my answers are the following:

- What camera body do you use? Canon 5D MKII

- What mode do you shoot in? AV

- What AF mode do you use? Auto-Focus

- Do you select a focus point, or do you let the camera choose for you? I always shoot with the central focus point and recompose with the use of the AF-ON back button.

- Do you put the focus point on a high-contrast edge? Or do you just point the camera in the general direction of what you are trying to photograph? I'm not sure I understand this topic here... Can you be more specific?

- Do you focus first, then shoot? Or do you just press the button? I use the halfway shutter to focus, sometimes what I actually want in focus is in the middle, so I don't recompose using the back-button, sometimes I do, so I use the back-button to lock focus and recompose.

And I think that is all, let me know if I need to answer something else other than this, please!

Thank you!

Thanks, that is good info. You use back-button AF, so you are not a complete novice.

Are you using one-shot AF? I assume so, but just checking.

When you focus using the center point, is it always just the center point that lights up when you achieve focus, or do other focus points sometimes turn red? In other words, do you have AF point selection set to "Automatic selection" or is it set to "Manual Selection", and you have selected the center point?

Turn on the option to display the AF point. This will put a red cross where the AF point is, so you can review in the camera if you are focusing where you think you are. The red cross doesn't actually end up on your final image, so don't worry about that. Make sure the red cross is always in the center, and not some other random point. The camera will not know that you recomposed, so it won't leave the red dot on what you actually focused on, though.

There is a geometry problem with the focus-recompose method. When you focus on something, and then move the camera to recompose, you are tilting the focus plane, and the object you want to focus on can move out of focus. This is more of a problem with wide apertures and short distances. If the subject is sufficiently far away, and you shoot stopped down enough, the focus-recompose trick works fine. But shooting close objects with wide-apertures (and thus thin depth of field) can be a problem if you focus-recompose.

Also, if you are shooting one-shot focus-recompose, there is a time lag between when you focus and when you release the shutter. Things can move in that time period - the subject, yourself, and you obviously just moved the camera. That time lag can allow things to drift out of focus, especially with thin DOF.

If you watched the video I referenced, you saw that the AF sensors are looking for high-contrast edges to focus on. If you put the focus point on something with little contrast, you will often have focus problems. Make sure you are always putting the focus point on a high contrast edge, preferably, or part of the subject that has good texture and contrast.

Here is a good article on focusing with wide aperture lenses: http://www.lensrentals.com/blog/2010/10/how-to-shoot-with-wide-aperture-lenses.  Although the picture you show is at f/4, not f/1.4, that is still pretty shallow DOF with a full frame camera at that distance.  One suggestion I like from that article is to shoot using the center point, but don't recompose.  Just shoot with enough extra room around the subject so that you can compose it by cropping in post.  With 20 MP, you have a lot of flexibility to crop with the 5D2, and you will never notice unless you print huge.

Check how well your camera/lens combo is focusing by taking as many variables out of the equation as possible.  Put the camera on a tripod, use a remote release, point the camera at something with a high contrast edge and take a picture.  Then zoom in with 10X mag to check the focus (or shoot tethered to a computer and check focus there).  You might try shooting at a row of batteries angled so some are at various distances.  You can then see if the camera is front-focusing or back-focusing.  If you see a consistent pattern at various subject distances, you may need to use the MFA feature of your camera.

ClaudiaC wrote:

Hello Bill! Thank you for all those questions, I do understand the need of those and I am sorry for not providing more information. So my answers are the following:

- What camera body do you use? Canon 5D MKII

- What mode do you shoot in? AV

- What AF mode do you use? Auto-Focus

- Do you select a focus point, or do you let the camera choose for you? I always shoot with the central focus point and recompose with the use of the AF-ON back button.

As the other poster pointed out, this can be an inaccurate method. With f1.4 you have shallow depth, so be turning/rotating your main subject is easily out of focus. I do notice that your sample seems to be shot at f4, so it should be less of an issue. However, 1/60 shutter speed with a 50mm lens is close to hand-held limit. If you are not careful, you easily can have a little camera shake.

It is perhaps best to make sure that your lens does perform correctly by putting it on a tripod and shooting something like a newpaper on the wall in good light. There is also a battery test you can perform to see if you have front or back focus (which can be corrected with your body).

- Do you put the focus point on a high-contrast edge? Or do you just point the camera in the general direction of what you are trying to photograph? I'm not sure I understand this topic here... Can you be more specific?

- Do you focus first, then shoot? Or do you just press the button? I use the halfway shutter to focus, sometimes what I actually want in focus is in the middle, so I don't recompose using the back-button, sometimes I do, so I use the back-button to lock focus and recompose.

And I think that is all, let me know if I need to answer something else other than this, please!

Thank you!

Ah! So you use AI servo.  The story becomes more interesting.

AI servo is not great on the 5D2, but can work OK with the center point, especially if you are not trying to track something moving extremely fast, and you have good light.

Back-button AF on the 5D2 is a little different than with the 5D3 that I'm using now, and I forget all the nuances of the menu settings on the 5D2.  The video I pointed you to by Rudy Winston was done back in those days, though, so he should be able to cover the settings.

Anyway, you need to lock focus somehow if you recompose while using AI servo, otherwise the camera will just continue to focus using the AF point where you move it to. So maybe you can go into some details about how you go about doing that, since there are several possible ways.

Also, maybe you can give details on how you select the center point for focusing, and if you use AF point auto expansion.

Any other relevant AF menu settings would be good to know, as well.  What are CF III-3, CF III-7, CF IV-1, CF IV-2 set to?  Do you have CF III-8 set to something other than disable?

billythek wrote:

Ah! So you use AI servo. The story becomes more interesting.

AI servo is not great on the 5D2, but can work OK with the center point, especially if you are not trying to track something moving extremely fast, and you have good light.

Back-button AF on the 5D2 is a little different than with the 5D3 that I'm using now, and I forget all the nuances of the menu settings on the 5D2. The video I pointed you to by Rudy Winston was done back in those days, though, so he should be able to cover the settings.

Anyway, you need to lock focus somehow if you recompose while using AI servo, otherwise the camera will just continue to focus using the AF point where you move it to. So maybe you can go into some details about how you go about doing that, since there are several possible ways.

Yup, good point, the point of AI servo is usually that it continues focusing as you shoot to track moving things that stay under the focus points. In this situation standard focus and recompose will not achieve the right focus, in the sample you show it will refocus on the space between the babies. It seems you are not using the right mode for the intended purpose.

Also, maybe you can give details on how you select the center point for focusing, and if you use AF point auto expansion.

Any other relevant AF menu settings would be good to know, as well. What are CF III-3, CF III-7, CF IV-1, CF IV-2 set to? Do you have CF III-8 set to something other than disable?

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- Bill

I'm a little fuzzy on the way back-button AF works on the 5D2. Do you know that AF-on will lock focus in this way in AI servo with the settings you have? You might think of some way to test this with your camera. If you lock focus on something close by and then turn the camera on something else far away and take a picture should prove the point. If the new subject is out of focus it would imply that focus lock did happen. You can probably figure out other tests to do.

If you are locking focus in this way, then your issue may just be due to the focus-recompose geometry issue I mentioned. The usual fix for this is to use the outer focus points to focus with, but those don't work all that well with the 5D2.

You might try the focus no-recompose method for awhile (compose by cropping) just as a test to see if that is the root of the problem.

Your settings show that you do have center point auto expansion enabled, so there is a chance that the focus point is not quite where you think it is. It may have strayed over to one of the expanded points. It may be worth playing with that setting to see if it has an effect on your problem. It is a useful setting for tracking subjects that are moving, but may complicate your AI servo focus recompose method.

You might also try one-shot for these kind of shots, just to see what effect that has. I use AI servo on static subjects with the 5D3 without many problems. However, I don't focus-recompose while doing that. I will either focus using outer points or compose by cropping (or a combination of the two).

Anyway, I'm about out of ideas. Study up, experiment, and let us know what you figure out. Or maybe someone else that is more familiar with the 5D2 can advise. It is hard to believe I have forgotten so much about the 5D2 in just one year.
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- Bill

ClaudiaC wrote:

I have a 50mm 1.4 for more than a year, but some focus issues have been happening more and more recently.

I have read a lot about focus issues on this lens in particular, but I wonder if this is something about the lens or about what I'm doing.

Any tips? I feel do frustrated when this sort of thing happens and it has been quite frequent lately.

Thank you!

I took some shots with my 50 1.4 today and noticed how badly front-focused my shots were (very similar to what you've gotten).

I had previously set the camera to us a MFA value of -2, tested under a number of situations where I had consistently good results.

Today, I had to use a MFA of +8 on the lens to get shots in focus. My lens was never dropped or subjected to any abuse and I have no idea why the lens all of a sudden changed its calibration so much. Perhaps it's the temperature change? Humidity?

This sis one reason maybe, when you put the lens cap on you apply pressure to the focus gear or even if you store the lens face down you have the same issue. The focus gear on the 50 1.4 is very fragile for want of a better term and goes out of shape very easily.

The results is the camera doesn't focus correctly, the elements are not all in place.