AF Microadjustment

[Zeee]

Came across a more recent Guide today. 2016. Page 5 has some interesting info.

First time I have seen Canon mention the light source. I use FoCal and there are instructions not to use fluorescent or any source that flickers but not temperature. Since I use my 100-400 II outdoors 90% of time I purchased two studio daylight balanced CFL's to light the target. I turn other close light sources off try to put the target close to a window if sunny. It is mentioned that incandescent will work and it does but I figured I may as go all the way and they aren't that expensive.

If anyone is interested I found this a while ago. You can get them at Home Depot, etc.

Flickering Fallacy: The Myth of Compact Fluorescent Lightbulb Headaches

Does the flickering of CFL bulbs cause headaches?

www.scientificamerican.com

The first time I have seen Canon combine your usual shooting distance and 50X.

You can download the PDF from here.

http://www.learn.usa.canon.com/resources/articles/2016/af-microadjustment-landing.shtml

 

[Johnw12]

Thank you for the information.

 

[Andy01]

I saw this thread and thought I was going nuts because I had already replied.

I did - in the duplicate thread you started in the FF forum. Here is my reply from there;

I would have thought that most people would do the MFA on a 400mm lens outside, since even with a FF, the 50x FL = 20m = 66', which would not be possible in many people's homes I suspect. Obviously on a APS-C body, the problem is 1.6x bigger - 32m / 106'.

I do all of my MFA outdoors, even at 24mm on a FF.

You generally only need to post in one forum, and avoid duplicates. The mods sometimes get cranky about duplicates.

Colin

 

[Zeee]

I saw this thread and thought I was going nuts because I had already replied.

I did - in the duplicate thread you started in the FF forum. Here is my reply from there;

I would have thought that most people would do the MFA on a 400mm lens outside, since even with a FF, the 50x FL = 20m = 66', which would not be possible in many people's homes I suspect. Obviously on a APS-C body, the problem is 1.6x bigger - 32m / 106'.

I do all of my MFA outdoors, even at 24mm on a FF.

You generally only need to post in one forum, and avoid duplicates. The mods sometimes get cranky about duplicates.

Colin

Yeah I know. I'm on both forums but took the chance. Just trying to help and there may be people who don't own both crop and FF.

 

[Lemming51]

...I would have thought that most people would do the MFA on a 400mm lens outside, since even with a FF, the 50x FL = 20m = 66', which would not be possible in many people's homes I suspect. Obviously on a APS-C body, the problem is 1.6x bigger - 32m / 106'.

I don't think it is obvious. The Canon recommendation is the user's usual shooting distance with the lens, or 50x focal length. Both are without regard to the size of the sensor.

 

[Andy01]

My bad, I thought I had read somewhere that it was effective length, not stated focal length.

Colin

 

[Lemming51]

My bad, I thought I had read somewhere that it was effective length, not stated focal length.

Thinking a little more on it, I think you were right even though it's not mentioned in the Canon directions.

e.g. 10mm on APS_C would be used for the same compositions and same focus distance as 16mm on full frame. And 400mm same as 640. So if 50x focal length is the recommended focus distance for full frame (16mm x 50 = 8m) then I agree you'd use the same distance (1.6 x 50) on APS-C equivalent lens (10mm x 50 x 1.6 = 8m).

--
Unapologetic Canon Apologist

 

[WilbaW]

My bad, I thought I had read somewhere that it was effective length, not stated focal length.

Thinking a little more on it, I think you were right even though it's not mentioned in the Canon directions.

e.g. 10mm on APS_C would be used for the same compositions and same focus distance as 16mm on full frame. And 400mm same as 640. So if 50x focal length is the recommended focus distance for full frame (16mm x 50 = 8m) then I agree you'd use the same distance (1.6 x 50) on APS-C equivalent lens (10mm x 50 x 1.6 = 8m).

AFAIK Canon have never stated why they specify 50f, so we have no idea how arbitrary or precise that number is. It wouldn't surprise me at all if 10mm x 50 = 5m and 16mm x 30 = 5m both work equally as well in every possible way.

 

[Zeee]

My bad, I thought I had read somewhere that it was effective length, not stated focal length.

Thinking a little more on it, I think you were right even though it's not mentioned in the Canon directions.

e.g. 10mm on APS_C would be used for the same compositions and same focus distance as 16mm on full frame. And 400mm same as 640. So if 50x focal length is the recommended focus distance for full frame (16mm x 50 = 8m) then I agree you'd use the same distance (1.6 x 50) on APS-C equivalent lens (10mm x 50 x 1.6 = 8m).

AFAIK Canon have never stated why they specify 50f, so we have no idea how arbitrary or precise that number is. It wouldn't surprise me at all if 10mm x 50 = 5m and 16mm x 30 = 5m both work equally as well in every possible way.

I think they picked a higher value to be sure people are well beyond where a lens settles down. Less support calls maybe.