7D AF spot problem

[Tabazan]

No wind.


One thing seems strange to me : spot AF is very sensitive, but in this case, if it had missed, something just behind or beside would be sharp, no ? . If you check the balconly, it

[Tabazan]

In the same vein, I

[HDNitehawk]

Do you think reinstalling the firmware (my 7D is on 1.2.3) could change something to AF adjustment/bug ??

I doubt it if you already have the latest version which is 1.2.3. But it won't hurt anything either.

[Richard Lane]

No wind.


One thing seems strange to me : spot AF is very sensitive, but in this case, if it had missed, something just behind or beside would be sharp, no ? . If you check the balconly, it's quite sharp but it's not in the same plan (much more in front).
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Yes, it does seem strange. HDNitehawk had some good suggestions, to help identify the problem.


Tripod to eliminate camera motion, stationary subject to eliminate subject motion, and try2 different lenses if you have them. Also try to get squared to same plane as your subject, as opposed to shooting on an angle.


Please forgive me if I am over simplifying this, since I don't know your level of experience with Canon, but if you are in One shot mode, then make sure that the red square is lined up on your target and then press the shutter button half-way to achieve focus lock. You should then hear the beep and then press the shutter button the rest of the way to take the photo.


Just remember, it is more important where focus lock was initiated, and not where the red square ends up, as occurs in re-composition.

[conropl]

Just remember, it is more important where focus lock was initiated, and not where the red square ends up, as occurs in re-composition.
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Rich:


This is kind of the discussion we got into about a week ago in the "post your best bird shoots" post. You were nice enough to try and help me out, and I said I would post some examples. I have not had a lot of time to do so, but this post seems to be addressing the same issue... so here is what I have found.


All shots below were with taken with a 7D, 100-400L @ 400mm and f/7.1


My problem has been when trying to focus when the background is cluttered (or has better contrasting feature as compared to the subject). In my case I was trying to shot Sand Cranes in a cornfield.


What seems to be happening is the spot size is bigger than the square, and it tends to focus on the higher contrast background. This is true even at wide open aperture... I closed it down some just in hopes that I could get a better DOF so I could focus on the body and get a sharp eye. (did not work to good though).


The shots below were not intended to be great pictures. I was just trying to figure out the AF problems in a difficult situation.


This first shot was in "One-Shot" mode and "Spot Focus". The focus point was confirmed to be centered on the head of the bird in the middle. It is totally out of focus. In this case the camera was well supported, and I pushed the shutterbutton half way a dozen times and got focus confirmation but was always out of focus.


[img]/resized-image.ashx/__size/800x1200/__key/CommunityServer-Components-UserFiles/00-00-00-66-81/8124_2800_centered-on-head_29002800_one_2D00_shot_2900_.JPG[/img]


Next I switched to AI-Servo with Spot Focus. This next shot was AI Servo and the spot was centered on the head. However, I had to move the spot back and forth over the head until it would final register the head as the focal point only for an instant, and then I would quick take a quick picture to get something half way decent. Still difficult to get a good focus, and it is fleeting.Also, the bokeh is horrible.


[img]/resized-image.ashx/__size/800x1200/__key/CommunityServer-Components-UserFiles/00-00-00-66-81/7904-_2800_on-head_2900_.JPG[/img]


At this point I pointed at the base of the neck and could get it to focus pretty easily... so this next one is focused on the base of the neck (spot smaller than subject). Still horrible bokeh.


[img]/resized-image.ashx/__size/800x1200/__key/CommunityServer-Components-UserFiles/00-00-00-66-81/7907_2800_Base-of-neck_2900_.JPG[/img]


Since the bokeh was so distracting, I then spent some time blurring the back ground in post processing. This helped, but still not great (see next one)


[img]/resized-image.ashx/__size/800x533/__key/CommunityServer-Components-UserFiles/00-00-00-66-81/7883_2800_Blured-background_2900_2.jpg[/img]


To give you an idea of the lens ability without the distracting background confusing the AF - below is the same lens, but the background is nice blue water and the spot was just under the eye (but the head was covering most of it).


[img]/resized-image.ashx/__size/800x1200/__key/CommunityServer-Components-UserFiles/00-00-00-66-81/7698_2800_ai-under-eye_2900_.JPG[/img]


I must say, I do not usually have a problem with AF, but the spot needs to be smaller than the subject (which means getting close). If the spot is larger than the subject, then the background and type of background can effect the focus a lot. Also, AI-Servo does help in cluttered background situation, but it is hit and miss and does not hold focus long.


Sorry for the long post. If anyone has a good idea on how to set up a shot better to overcome these problems in corn fields... I am open.


Pat

[Fast Glass]

Man, I liking manual focus even better now![:P] Well, at least I don't feel like I'm missing as much as I thought.


John.

[Tabazan]

Thanks a lot to you all.


I've learned a lot whith your advices []


I will work a bit more on the "lock" aspect, make some test too and train the specific use of the various AF options.


Have a great day !

[neuroanatomist]

specific use of the various AF options

Here are some links that may help out:


Canon DLC 7D video tutorials - short videos on each of the AF modes, among other topics


Canon DLC article on 7D AF modes


Canon DLC article on back-button AF


--John

[hirosz]

Have you found a solution? I have this same problem with my canon 7d.


examples:


img853.imageshack.us/.../test3g.jpg


img845.imageshack.us/.../test1q.jpg


img190.imageshack.us/.../test4n.jpg


img846.imageshack.us/.../test2y.jpg

[Richard Lane]

Just remember, it is more important where focus lock was initiated, and not where the red square ends up, as occurs in re-composition.
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Rich


My problem has been when trying to focus when the background is cluttered (or has better contrasting feature as compared to the subject). In my case I was trying to shot Sand Cranes in a cornfield.


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<span style="font-size: small;"]This is a difficult situation, but I can assure you that the 7D is capable of getting these shots!


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What seems to be happening is the spot size is bigger than the square, and it tends to focus on the higher contrast background. This is true even at wide open aperture... I closed it down some just in hopes that I could get a better DOF so I could focus on the body and get a sharp eye. (did not work to good though).


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<span style="font-size: small;"]I understand you are using spot focus in order to get around the branches in the foreground and this may be an acceptable use, and if it was working for you then I would say stick with it, however since it's not working then I say lets change it up.


<span style="font-size: small;"]The spot AF sensor does not have to be bigger than the object that it is focusing on. The spot auto focus point just has to be smaller than any obstructions in the foreground which may block it's acquisition of your subject.


<span style="font-size: small;"]If the AF sensor point is half on your subject and half on the background, then it will lock on the closest point to the sensor. All that the "smaller spot" sensor point is doing is making it more difficult for you to lock onto your subject, and it is also making it easier for the small square to fall off of your target and grab onto the background.


<span style="font-size: small;"]The spot sensor point is actually larger than it appears in the view finder and the single point sensor is actually smaller than it appears in the VF. All of the AF sensors should lock in on the closet point and not the background.


<span style="font-size: small;"]"One thing that I did notice was that you and Tapazan were both using a Spot Focus Point with One Shot."


<span style="font-size: small;"] If you use one shot, with "spot" focus point, and press and hold down the shutter button in high speed burst mode, and you miss your target, then you will miss every shot after that. This occurs because the AF will lock-in on something in "one shot mode" so if you grab the background by accident for the first shot, then every other shot following the initial one will be focused on the background so "every shot will be OOF." You should try this at home.


<span style="font-size: small;"]

<span style="font-size: small;"]The shots below were not intended to be great pictures. I was just trying to figure out the AF problems in a difficult situation.


This first shot was in "One-Shot" mode and "Spot Focus". The focus point was confirmed to be centered on the head of the bird in the middle. It is totally out of focus. In this case the camera was well supported, and I pushed the shutterbutton half way a dozen times and got focus confirmation but was always out of focus.


[img]/resized-image.ashx/__size/800x1200/__key/CommunityServer-Components-UserFiles/00-00-00-66-81/8124_2800_centered-on-head_29002800_one_2D00_shot_2900_.JPG[/img]


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<span><span style="font-size: x-small;"]Next I switched to AI-Servo with Spot Focus. This next shot was AI Servo and the spot was centered on the head. However, I had to move the spot back and forth over the head until it would final register the head as the focal point only for an instant, and then I would quick take a quick picture to get something half way decent. Still difficult to get a good focus, and it is fleeting.Also, the bokeh is horrible.





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<span style="font-size: small;"]The reason that you had some success with the AI Servo mode was because since AF was not locked, your "small Spot" sensor point would sometimes grab the background and sometimes grab your subject, since AI Servo does not lock in on one or the other. AI Servo is constantly trying to lock onto and track something, so sometimes you're getting lucky. Therefore, when you use burst mode under these conditions some will be in focus and some won't.


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[img]/resized-image.ashx/__size/800x1200/__key/CommunityServer-Components-UserFiles/00-00-00-66-81/7904-_2800_on-head_2900_.JPG[/img]


At this point I pointed at the base of the neck and could get it to focus pretty easily... so this next one is focused on the base of the neck (spot smaller than subject). Still horrible bokeh.


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<span style="font-size: small;"]Remember that the AF red square does not have to be smaller than the subject, as long as it hits your subject and not the foreground. The spot AF is good for shooting in between a soccer net, face-mask on a helmet, or in between branches like you're doing, but if your subject is moving or is very far away, then it just makes it more difficult to hit your target.


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To give you an idea of the lens ability without the distracting background confusing the AF - below is the same lens, but the background is nice blue water and the spot was just under the eye (but the head was covering most of it).





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<span style="font-size: small;"]Excellent shot that is also very sharp!


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[img]/resized-image.ashx/__size/800x1200/__key/CommunityServer-Components-UserFiles/00-00-00-66-81/7698_2800_ai-under-eye_2900_.JPG[/img]


Also, AI-Servo does help in cluttered background situation, but it is hit and miss and does not hold focus long.


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<span style="font-size: small;"]As stated above, AI Servo will constantly search for the nearest AF point that is captured on the AF sensor, so sometimes you will get your subject and sometimes you will get the background, especially if your AF point and your subject are moving, which is occurring in this case. However, if set up properly with other custom functions, then you should definitely nail most of your shots.


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