50D Micro AF Adjustment Help.

Candid Arts

So I am doing the micro AF Adjustment on my 50D. I did my 24-105 lens and had to do a +5 adjustment. Now I'm on to my 10-22. I got it narrowed down to -3, -2, -1, 0, +1, +2, or +3. I can't seem to see a difference though in which one is sharpest. Can I get some help? Thanks!

Here are the Images in sequential order:

-3:


-2


-1


0


+1


+2


+3


Thanks for anyone's help.

Shootin1st

What was your specific focus point?

Candid Arts

I used the center AF point only. Dead center of the photos posted.

Qarik

how far were you away, what zoom and aperature were you using?

Candid Arts

Qarik wrote:

how far were you away, what zoom and aperature were you using?

I was maybe...15 feet away. 10mm, ISO 100, f/3.5, 1/250th, RAW, Mirror Lock-Up, Steady tripod. Edited just the way the "How-To" was posted in the thread by Scott_Quier here.

Scott_Quier

Candid Arts wrote:

I was maybe...15 feet away. 10mm, ISO 100, f/3.5, 1/250th, RAW, Mirror Lock-Up, Steady tripod. Edited just the way the "How-To" was posted in the thread by Scott_Quier here.

Re-shoot it, but this time put the center focus point right below the dark spot on the right side of the tree. Doing this will allow you to find the line where things go soft and you can then see which direction you need to look for a better sharpness. Focusing on a plane surface (and for this exercise, the front aspect of the tree is close enough to a plane surface for our purposes) just don't supply you with enough information to make it as easy as possible.

Candid Arts

Scott_Quier wrote:

Re-shoot it, but this time put the center focus point right below the dark spot on the right side of the tree. Doing this will allow you to find the line where things go soft and you can then see which direction you need to look for a better sharpness. Focusing on a plane surface (and for this exercise, the front aspect of the tree is close enough to a plane surface for our purposes) just don't supply you with enough information to make it as easy as possible.

I will do that. It'll have to wait for another day though as the sun has now set, plus it's dinner time....

tonyd

What about using the method described here:

http://www.focustestchart.com/focus21.pdf

It's a long document but basically requires taking photos of the chart on page 18 (at a 45 degree angle) to help pinpoint the correct focus.

I've used this method on a few lens and it seemed to work out pretty good.

Scott_Quier

Candid Arts wrote:

I will do that. It'll have to wait for another day though as the sun has now set, plus it's dinner time....

I've re-written a critical portion of my description to read:

Find a subject that has a variable distance from you camera - I use a tree trunk in my back yard. I focus on a spot on the trunk of the tree about half way between the "front surface" (from my perspective) of the trunk and the very edge. Doing this allows me to compare where on the trunk of the tree the camera/lens is actually focusing with where I had intended it to focus. When these two points coincide, I know I have achieved a proper adjustment. Working with only a flat, square on surface can only tell you that you have (or don't have) focus.

I think/hope this will better explain what I am trying to convey.

Scott_Quier

tonyd wrote:

What about using the method described here:

http://www.focustestchart.com/focus21.pdf

It's a long document but basically requires taking photos of the chart on page 18 (at a 45 degree angle) to help pinpoint the correct focus.

I've used this method on a few lens and it seemed to work out pretty good.

I tried that and a couple of other techniques. They may work for others just fine but they failed for me. Maybe because I may not be the sharpest tool in the shed.

Everyone needs to use what works for them.

Qarik

DOF calculator says at 15 feet and 10mm zoom and fstop 3.6 (no 3.5 option) your DOF is 3.6 feet in front to infinity behind. I think to make this more precise..you will have to focus something very close and at the highest end of your zoom with fastest fstop you have. Then should be able to see more of differentiation.

Candid Arts

Qarik wrote:

DOF calculator says at 15 feet and 10mm zoom and fstop 3.6 (no 3.5 option) your DOF is 3.6 feet in front to infinity behind. I think to make this more precise..you will have to focus something very close and at the highest end of your zoom with fastest fstop you have. Then should be able to see more of differentiation.

Couple points to that, the "How-To" I followed by Scott said to shoot at something at a normal distance you would shoot with that lens. I normally shoot that lens at 10mm also... And 3.5 is wide open.

But I definitely see your point.

Qarik

Candid Arts wrote:

Couple points to that, the "How-To" I followed by Scott said to shoot at something at a normal distance you would shoot with that lens. I normally shoot that lens at 10mm also... And 3.5 is wide open.

But I definitely see your point.

For instance if you go to 20mm and say 3 feet with 3.5 fstop the DOF drops to about about 11 inches. You say you shoot mostly at 10 mm though, so I suppose this assumes that the micro adjustment at 20mm is valid at 10mm which I would guess to the 1st order it is.