AF Fine Tune for Zooms?

Joined
Feb 1, 2008
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Location
Stockton,CA
Sorry if I'm beating a dead horse, but I must ask. Does the AF Fine tune matter with Zooms since all the focal lengths might vary the front/back focus issues with some users? I'm looking at Jeffrey Friedl's blog about the front/back focus issues, and it says to keep the camera square with the chart on a flat surface, so is the camera at a certain angle looking at the chart? I'll be testing my 28-75 and at 28mm, there is a lot of DoF, so is there a point testing at 28? I guess testing from 50 -75 will be better. Thanks for the help!

Link to Jeffry Friedl's blog.

http://regex.info/blog/photo-tech/focus-chart

The lens align looks nifty, but a little expensive.
 
Joined
Feb 12, 2009
Messages
3,678
Location
St Louis MO
you can move closer that will make the DOF smaller

for zooms you only get one setting in the camera....

so if at 28 you need -1 and at 75 you need +3 you have 2 choices

1. pick on and leave it

2. take the "average" at +2

3. change it


also make sure you camera can't lock onto the gray area, if it can print the grades down untill it cant. i had to the 5% on my D90
I'd hope your lens isn't that far off but it could be.....
 
Joined
Feb 1, 2008
Messages
687
Location
Stockton,CA
you can move closer that will make the DOF smaller

for zooms you only get one setting in the camera....

so if at 28 you need -1 and at 75 you need +3 you have 2 choices

1. pick on and leave it

2. take the "average" at +2

3. change it


also make sure you camera can't lock onto the gray area, if it can print the grades down untill it cant. i had to the 5% on my D90
I'd hope your lens isn't that far off but it could be.....

K thanks, I'll try it. I was at 25% and i guess it was locking onto the gray, I'll try it again tomorrow, but from what I've tried so far. It looks like it wasnt off by a great amount, to my eye it, at any amount it looks the same +20, 0 , -20. I didn't see a great great difference, but I did see some changes, but not huge changes. Could be the camera was locking on to the 25% gray? My set up was with a tripod, and the chart on a very flat table. My camera was at 45ish degree. I tested a 75, 60, 50 , and it didnt look like a great difference, but I'll try it again tomorrow.

What does he mean, keep the camera square with the chart?
 
Joined
Apr 5, 2008
Messages
2,847
Location
Middletown, NY
[QUOTE

What does he mean, keep the camera square with the chart?[/QUOTE]

It means level. So you can get an accurate horizontal read of where the focus point is sitting in the DOF viewing from left to right. If you are square with the chart, the numbers on the left side and right side will be at the same level when you download the chart. You must do the best you can to make the chart even and centered when looking through the viewfinder.

Mike
 
Joined
Feb 1, 2008
Messages
687
Location
Stockton,CA
[QUOTE

What does he mean, keep the camera square with the chart?
It means level. So you can get an accurate horizontal read of where the focus point is sitting in the DOF viewing from left to right. If you are square with the chart, the numbers on the left side and right side will be at the same level when you download the chart. You must do the best you can to make the chart even and centered when looking through the viewfinder.

Mike[/QUOTE]

Thanks, so the I'm assuming the chart is at an angle, and the camera is dead on the chart? And having the lines the same level as left and right.
 
Joined
Jul 28, 2006
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Location
Paris, France
I had never thought of that but it does seem to make a lot of sense ! In any case I don't pixelpeep so it's not all that important but now I have one more argument to tell those who are obsessive about their lens' sharpness :tongue:
 
Joined
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Messages
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Location
Middletown, NY
[/QUOTE]Thanks, so the I'm assuming the chart is at an angle, and the camera is dead on the chart? And having the lines the same level as left and right.[/QUOTE]

Yes, your camera will be shooting at a 45 degree angle, but the DOF will be straight from left to right.

While it could be better, here is a fairly square shot of a chart:

sorry for the large size,

Subscribe to see EXIF info for this image (if available)
 

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