AF microadjustment tricks

[Jim Zipp]

Pretty cool Arash. Never even heard of that method before. My gear is with CPS for the second time now. Mine needed too much MA with some lenses and have all hopefully being calibrated now. If I adjusted for razor sharp images at a closer distance my further shots were soft. I understand Canon uses different methods to do this and want to be at least starting from 0 or closer to it. Thanks.

[arash_hazeghi]

Pretty cool Arash. Never even heard of that method before. My gear is with CPS for the second time now. Mine needed too much MA with some lenses and have all hopefully being calibrated now. If I adjusted for razor sharp images at a closer distance my further shots were soft. I understand Canon uses different methods to do this and want to be at least starting from 0 or closer to it. Thanks.

Hi Jim,

Hope it works out for you, have seen the comments about MKIV but don't have that camera so I don't know why this is happening. One other issue is that if AF sensor is slightly miss aligned with respect to the beam splitter it will give soft images no matter what you do, you can verify this by using live view AF at different distances to see if it can focus properly.

Best

[Jim Zipp]

One other issue is that if AF sensor is slightly miss aligned with respect to the beam splitter it will give soft images no matter what you do...
Best

Thanks Arash, but I am getting some super sharp images.... just not at varying distances. Smaller birds and anything within about 60 feet are killer sharp after dong MA but that threw further subjects off. That mirror for aligning the target is a great idea.

[arash_hazeghi]

Thanks Arash, but I am getting some super sharp images.... just not at varying distances. Smaller birds and anything within about 60 feet are killer sharp after dong MA but that threw further subjects off. That mirror for aligning the target is a great idea.

In this case only Canon can help, hope they fix your gear soon!

[paul leverington]

Hi Jim,

One other issue is that if AF sensor is slightly miss aligned with respect to the beam splitter it will give soft images no matter what you do, you can verify this by using live view AF at different distances to see if it can focus properly.

Best

Jeez this sounds like what I have been battling. I sent my rig in to be zeroed and when I got it back did some near and far testing for MA and everything looked gret at a setting of zero. However all shots were OOF. Only through testing in the field and adjusting everyday till I got a value of +9 has everything come into focus. But in servo on moving subjects I'm lucky to see one in 25 real sharp. But I have always been seeing different results for different distances.

Arash you've done us all a great service with posting this--and a nice thorough job of it. Where did you read up on this or is it your own concoction? I think if I knew more on the working intracacies of AF I'd be better able to diagnose things.

Paul

[Don Saunders]

At first glance, this method looks OK. But, there is a BIG weakness. Suppose you are checking the focus of your 400mm f/5.6 lens. At f/5.6, there is a fair amount of depth of field at 33 feet distance from the target (the recommended distance for a 400mm lens). You could look at a flat target and see that your lens is in sharp focus. But what you cannot tell from a flat target is how much is in focus in front of the target and how much in back of the target. In other words, within the depth of field zone, where is your lens focusing?

I use the LensAlign system which incorporates a flat focusing target and an angled ruler. The camera focuses on the flat target and the ruler shows you very clearly where your depth of field focus "zone" lies. Having just done this with fellow Canon shooter, we saw his lens was in complete focus on the target. But most of the depth of field "zone" was in front of the target. Remember the rule of thumb, one third of the zone in front and two thirds behind. Using the LensAlign, we were able to calibrate precisely his 400mm lens on his 7D with one third in focus in front of the target and two thirds behind the target. Almost like focusing on an imaginary flying bird.:D

You would encounter this same issue on all big lenses - 300, 400, 500, 600, and 800. Don't you want to control the exact position of your depth of field? A flat focusing target will not show you this.

I do not work for LensAlign. I paid for my LensAlign just like everyone else. I like it because it works and I can repeat and reproduce the results accurately every time. It is not cheap. But neither are the wonderful big lenses you own!

[arash_hazeghi]

At first glance, this method looks OK. But, there is a BIG weakness. Suppose you are checking the focus of your 400mm f/5.6 lens. At f/5.6, there is a fair amount of depth of field at 33 feet distance from the target (the recommended distance for a 400mm lens). You could look at a flat target and see that your lens is in sharp focus. But what you cannot tell from a flat target is how much is in focus in front of the target and how much in back of the target. In other words, within the depth of field zone, where is your lens focusing?

I use the LensAlign system which incorporates a flat focusing target and an angled ruler. The camera focuses on the flat target and the ruler shows you very clearly where your depth of field focus "zone" lies. Having just done this with fellow Canon shooter, we saw his lens was in complete focus on the target. But most of the depth of field "zone" was in front of the target. Remember the rule of thumb, one third of the zone in front and two thirds behind. Using the LensAlign, we were able to calibrate precisely his 400mm lens on his 7D with one third in focus in front of the target and two thirds behind the target. Almost like focusing on an imaginary flying bird.:D

You would encounter this same issue on all big lenses - 300, 400, 500, 600, and 800. Don't you want to control the exact position of your depth of field? A flat focusing target will not show you this.

I do not work for LensAlign. I paid for my LensAlign just like everyone else. I like it because it works and I can repeat and reproduce the results accurately every time. It is not cheap. But neither are the wonderful big lenses you own!

The purpose of MA is to align the sharpest focus plane with the precise location of subject, You can easily tell the location of focus plane within dof by using (>) or buttons (<), just click until you go oof each way and you can tell how many clicks you have in the front or back, more accurate than trying to read the cm scale on a ruler in a photograph. You can also then shift the focus plane within dof to your desired location while trying to maintain an acceptable sharpness if that is what you want to do although I don't see the point as long as the sharpest plane is on the intended subject. If the sharpest plane is too froward or too backward in the dof zone, MA cannot fix this issue and one of the optical elements in the lens is misaligned, although I have never seen a lens like this.

Also you can use this method with any target not just a flat target, it doesn't really matter what target you use... it does matter for target be parallel to sensor though. The method is not about the target but by how you choose what value to dial in. The scale on a ruler does not correspond to the MA values in the camera menu, so you have to dial in values randomly and find the best by trial and error. Also the 200% magnified live video feed from sensor makes it a lot easier to judge edge sharpness than using camera's LCD, and the remote control operation allows for very fine stepping of the servo, not possible if you try to manually focus using the focus ring on the lens.

Any ways, of course you should use whatever method you like and feel more comfortable with that works for you.

[Ken Foss]

Arash, thank you very much for this thread! When focusing in live mode on my 7D I have observed that the center auto focus point is not focusing on the exact same location as when looking through the view finder. The difference is about half the width of the focus point. It is close, but not spot on. Not sure if this is normal and wondering if others have found the same thing. Ken

[arash_hazeghi]

Arash, thank you very much for this thread! When focusing in live mode on my 7D I have observed that the center auto focus point is not focusing on the exact same location as when looking through the view finder. The difference is about half the width of the focus point. It is close, but not spot on. Not sure if this is normal and wondering if others have found the same thing. Ken

Not sure I understand what you're saying, the active sensor is indicated with a red frame in the LV screen, within the red frame sensor will pick any point that has the highest contrast, this is normal.

Also make sure 7D is not in spot AF mode when performing MA.

[arash_hazeghi]

Jeez this sounds like what I have been battling. I sent my rig in to be zeroed and when I got it back did some near and far testing for MA and everything looked gret at a setting of zero. However all shots were OOF. Only through testing in the field and adjusting everyday till I got a value of +9 has everything come into focus. But in servo on moving subjects I'm lucky to see one in 25 real sharp. But I have always been seeing different results for different distances.

Arash you've done us all a great service with posting this--and a nice thorough job of it. Where did you read up on this or is it your own concoction? I think if I knew more on the working intracacies of AF I'd be better able to diagnose things.

Paul

Hi Paul,

I just came up with this when I was playing around with EOS utility, found that works well! As I mentioned MA will not help with random AF misses or soft images during tracking in AI servo mode, you should always do adjustment and testing for stationary subjects on tripod to diagnose any problems.

Good luck :)