Learn from my mistake: @%$(% diopter adjustment.

[krb]

I spent some time today shooting ospreys with a 100-400 lens and a 1.4x teleconvertor. Since AF won't work with this combination I had to manually focus but everything looked great through the viewfinder. Imagine my dismay when I got home and found that all of the MF shots were soft.

While swapping the batteries I noticed that the diopter adjustment had apparently gotten bumped around because it was off by 2 clicks. Just enough to cause all of the shots to be back-focussed just enough to make them all worthless.

Lesson learned: Always check the diopter adjustment before using manual focus.

[superstes]

Quick question.

When you manual focus, doesn't your center focus point light up anyway indicating focus achieved, or does the 1.4x tele cancel this.

[argyle]

The diopter adjustment will not have any effect on using manual focus...it merely allows you to fine-tune the AF function of the camera to your eyesight by sharpening the AF points in the VF when turning the wheel. If you have a sharp image when using AF, this means that your diopter adjustment is set properly. If you have a sharp image in the VF when using manual focus, but the resulting image looks soft, you have an issue with your focusing screen...this can usually be cured by adjusting the focus screen distance with the use of brass shims (available through Canon as "focus screen washers"). Also, as your focal length gets longer, the DOF will drop off considerably...adding a multiplier into the mix will reduce it even more and will have an effect on MF. Until I shimmed the focus screen in my 5D, I had to use focus bracketing when using fast, MF lenses (1.2, 1.4) because I had the same problem that you're describing...sharp image in VF, but out of focus after downloaded (mainly when the DOF was very shallow). Since I shimmed the screen, MF at wide apertures (shallow DOF) is right on the money.

[Lowner]

krb,

Interesting that the 40D, 100-400 and 1.4x won't work for you. I use a 30D and the same combination AF's perfectly. I use a Kenko PRO300 with the three pins taped as per the sticky instructions, and I gather the same trick works with the Canon TC.

[PhotosGuy]

When you get the diopter adjustment right, put a tiny drop of paint on it so you don't have to try adjusting it in low light.

[krb]

krb,

Interesting that the 40D, 100-400 and 1.4x won't work for you. I use a 30D and the same combination AF's perfectly. I use a Kenko PRO300 with the three pins taped as per the sticky instructions, and I gather the same trick works with the Canon TC.That's the important part. I'm also using the Kenko, but I normally use it with the 200 f/2.8 and 300 f/4 so there hasn't been a reason to have the pins taped.

[krb]

Quick question.

When you manual focus, doesn't your center focus point light up anyway indicating focus achieved, or does the 1.4x tele cancel this.
The only difference between AF and having the AF point light up during MF is that for AF the camera is using a motor to move the focus mechanism. If the camera could see well enough to correctly light up the AF point then there would be no reason that it couldn't also move the focus mechanism and AF.

[TwoShot]

When i got my xti,, I thought there was something wrong with the doipter,,, :mad:one time I would look thru it ,it would be clear, than maybe look at it again and not clear, darn I'am thinking i need to send It back to be looked at it.
Well i stewed on it for awhile.:mad:
Than a light poped on in my head hmmmmmmmmm,
Well to make a long story short, when adjusting it ,, think about weather you have your glasses ON or OFF. Makes a lot of differance.:o

[cerveza4lu]

Funny, when I first got my 20D I thought it was all screwed up because everything was OOF. Apparently the diopter adjustment was changed from the default setting. How to feel like a complete noob in 5 seconds or less!

[superstes]

The only difference between AF and having the AF point light up during MF is that for AF the camera is using a motor to move the focus mechanism. If the camera could see well enough to correctly light up the AF point then there would be no reason that it couldn't also move the focus mechanism and AF.

I understand MF, but you stated AF would not work with 100-400 and a 1.4x tele combo, my question was would the center focus point still illuminate in MF as normal or does the 1.4Xx tele cancel this too, it would not matter what your diopter adjustment was set too as long focus was confirmed in camera if I understand correctly.