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09-21-2018, 12:55 AM - 3 Likes   #1
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How to check your AF "point" coverage / sizes

If you want to check this, it is quite easy.
  1. Open something like Microsoft Powerpoint or a painting program to create a blank sheet that can cover the full screen in front of you. Turn the whole background black. Draw a square box in the middle of it in white - the size should be about 1/3 of screen height.
  2. Take your camera in AF.S mode and select one AF point you want to check.
  3. For easy use turn the output to JPG, smallest size XS.
  4. As drive mode select multiexposure composite and set it to 4 exposures.
  5. Set it to composite mode "bright addition".
    ---
  6. a) Now shot your screen, by starting to point the chosen AF point onto the center of the black area on top of the white square. Quickly repeatedly half-press the shutter button to make the AF search for a contrast edge which it initially should not find the the all black subject, so the AF should just hunt around.
  7. b) Very, very slowly move downwards towards the white box edge, all the time repeatedly half-pressing the shutter button.
  8. c) Once you get very close to it and actuall AF line sensor will identify the contrast edge and stop hunting and focus correctly. Now really press the shutter to take an image.
    ---
  9. Now repeat the last three steps three more times: coming from the right side, moving to the left; and from below moving upwards; and finally from the left side moving to the right.
  10. So in total you should have triggered four images, which the camera will combine into one.

The end result will show the size of the AF point as black box.

Repeat it a couple of times to get the hang of it and get some more reproducible results.

09-21-2018, 04:57 AM   #2
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QuoteOriginally posted by beholder3 Quote
If you want to check this, it is quite easy.
  1. Open something like Microsoft Powerpoint or a painting program to create a blank sheet that can cover the full screen in front of you. Turn the whole background black. Draw a square box in the middle of it in white - the size should be about 1/3 of screen height.
  2. Take your camera in AF.S mode and select one AF point you want to check.
  3. For easy use turn the output to JPG, smallest size XS.
  4. As drive mode select multiexposure composite and set it to 4 exposures.
  5. Set it to composite mode "bright addition".
    ---
  6. a) Now shot your screen, by starting to point the chosen AF point onto the center of the black area on top of the white square. Quickly repeatedly half-press the shutter button to make the AF search for a contrast edge which it initially should not find the the all black subject, so the AF should just hunt around.
  7. b) Very, very slowly move downwards towards the white box edge, all the time repeatedly half-pressing the shutter button.
  8. c) Once you get very close to it and actuall AF line sensor will identify the contrast edge and stop hunting and focus correctly. Now really press the shutter to take an image.
    ---
  9. Now repeat the last three steps three more times: coming from the right side, moving to the left; and from below moving upwards; and finally from the left side moving to the right.
  10. So in total you should have triggered four images, which the camera will combine into one.

The end result will show the size of the AF point as black box.

Repeat it a couple of times to get the hang of it and get some more reproducible results.
Interesting test. What is your result on K-1? Do different focus points differ in sizes?
09-21-2018, 05:02 AM   #3
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I did not invest time to check more than the central AF point and that was long ago.
09-21-2018, 05:05 AM   #4
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QuoteOriginally posted by beholder3 Quote
I did not invest time to check more than the central AF point and that was long ago.
so, what is the result?

09-21-2018, 05:27 AM   #5
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QuoteOriginally posted by Medex Quote
so, what is the result?
I know the size of the center AF point.
09-21-2018, 09:05 AM   #6
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Why in the step 6 you start from the white square center and in the step 9 you start from a side?
09-21-2018, 04:33 PM   #7
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Observations:

One picture is worth a thousand words.
If you want to talk about how big something is, show me, don't tell me.
If there is no photo, it didn't happen.

09-21-2018, 11:27 PM   #8
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QuoteOriginally posted by Andrea K Quote
Why in the step 6 you start from the white square center and in the step 9 you start from a side?
I dont understand what you refer to.

QuoteQuote:
a) Now shot your screen, by starting to point the chosen AF point onto the center of the black area on top of the white square. Quickly repeatedly half-press the shutter button to make the AF search for a contrast edge which it initially should not find the the all black subject, so the AF should just hunt around.
b) Very, very slowly move downwards towards the white box edge
Always start on the black background and move towards the white box in the center (from all four directions).

---------- Post added 22nd Sep 2018 at 08:30 ----------

QuoteOriginally posted by runswithsizzers Quote
Observations:

One picture is worth a thousand words.
If you want to talk about how big something is, show me, don't tell me.
If there is no photo, it didn't happen.


You need to read forum posts slowly and properly. Hint: The words "How to" in the title.
09-22-2018, 06:45 AM   #9
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Posts: 186
QuoteOriginally posted by beholder3 Quote
[...] Hint: The words "How to" in the title.
Yes, but it's a rare "how-to" article that does not benefit from illustrations / photos. And your process did generate a photo, right? And, this IS a photography forum.
09-23-2018, 02:29 PM   #10
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QuoteOriginally posted by beholder3 Quote
The end result will show the size of the AF point as black box.
Genius...


Steve
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