# Help on interpreting FoCal results



## polarhannes (Mar 13, 2013)

Hi,

I just tried Reikan FoCal with some of my lenses and I am unsure on how to interpret the results.
To me it seems like my 5D3 has issues in general (meaning if I focus on a matchstick it is OOF as it focusses a little bit in direction of the camera, if I get it right?). The last column shows the average adjustment. Would you set it to the average or shall I take the distance in which I use the lenses most?
Shall I send the camera and lenses in and if I do so, will they charge me? The camera and lenses should still be covered by warranty. Does the warranty cover adjustments?

Your thoughts and help are much appreciated!


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## digital paradise (Mar 14, 2013)

If your gear is under warranty then you will not be charged for adjustments.


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## Mt Spokane Photography (Mar 14, 2013)

You are checking the lens way beyond the recommended 25X to 50X range. There will be errors if closer or further away.

Your 70-200mm looks ok 

Something appears to need adjustment with your 100mmL, send it to Canon.

Your 40mm looks fine. 

Just use the AFMA to adjust the 70-200 and 40mm to a value between 2X and 50X the focal length for average use. 

The results are not really critical, there are too many error factors involved to get things perfect. A difference of +/- 4 or even 5 AFMA units is usually not a big deal.
Notice that the top of the AFMA curve is typicallyfairly flat.


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## robbymack (Mar 14, 2013)

Well your 70-200 I'd pick either +3 or 4. You're really splitting hairs at that point, either will be fine. The 100L, dunno, can you return it? I sort of figure any Afma adjustment that needs to be over 10 in either direction probably means I'm better off with another lens if I can get one. That however doesn't mean that the same lens is crap, just that your body and the lenses manufacturing tolerances multiply, in other cases they could cancel and give you a perfect result needing no adjustment.


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## polarhannes (Mar 14, 2013)

Thank you for your replies, much appreciated! 

I will set
70-200 = wide +3, tele +5
100 = +15
40 = +7

and see if Canon will repair/adjust the 100mm.
It is quite interesting, I used to have a 7D and the 100mm produced quite good results with that camera. This really shows that it is indeed a combination of camera body and lens.

Thank you all for taking the time to reply!


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## J.R. (Mar 14, 2013)

hjulenissen said:


> I have done several rounds of FoCal, and I still find it difficult. I get seemingly conflicting results depending on distance, lighting, moonphase and what not.
> 
> I am starting to suspect that AF inaccuracy (at least in my case) is as much about random error, as it is about a constant bias (only the latter can be reliably corrected).
> 
> -h



Moonphase ... L oh L ;D

There was the new moon a couple of days back ... maybe the OP did the FoCal back then ... explains the 100L ... BRILLIANT! ;D ;D ;D


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## polarhannes (Mar 14, 2013)

Had to laugh about the moonphase as well ;D

The 100L was tested using the same test setup I used for the 70-200 and 40 and on the same day.
I also changed the setup a couple of times between the tests just to make sure... Changed the distance, changed the light setup (daylight by using a large reflector, artificial light, ...), even put the target to different walls. The results varied a bit but still were close to each other ( 5, 6, 4, 6, ...)

At least you can get an impression by taking the average + or - setting or if a lens is completely off like my 100L.


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