focus test results...puzzling

[willg]

maybe this is a quick answer but i did tim jacksons focus test with my new 70-200 f4 and at 135mm its dead on and very sharp...but at 200mm the focus is back 10mm or so...anyone know whats going on?

[tim]

Can you post shots of your test chart at 70, 135, and 200mm? Make sure you use a tripod for all the shots.

[willg]

Can you post shots of your test chart at 70, 135, and 200mm? Make sure you use a tripod for all the shots.
ok so i don't really trust them because i didnt set it up very well, but what i do trust is the following picture...you can clearly see how the focus is off...it was handheld but the shutter was pressed immediately after i heard the focus beep and i used a flash

http://uploads.jzl.us/files/badfocusflower.jpg

[tim]

You can't do focus testing like that, please use a focus test chart. You can find one here

http://md.co.za/d70/chart.html

[willg]

You can't do focus testing like that, please use a focus test chart. You can find one here

http://md.co.za/d70/chart.html

ok thanks...i am just worried i won't set it up exactly at 45 degrees and all that...i will do it seriously tomorrow with daylight and a yard stick to make sure its as close to 45 degrees as possible

[Tom W]

ok so i don't really trust them because i didnt set it up very well, but what i do trust is the following picture...you can clearly see how the focus is off...it was handheld but the shutter was pressed immediately after i heard the focus beep and i used a flash

http://uploads.jzl.us/files/badfocusflower.jpg

I may be way off base here, but I cannot clearly see whether the focus is off or not. There is a lot of depth to the target, all of which can fall under the actual focus sensor (which is actually a good deal bigger than the size of the indicator square in the viewfinder). I think that your focus sensor found a good, contrasty boundary in the center of the flower, which seems to be in very good focus.

I agree with the others - use a better target for focus testing.

BTW, that is a pretty nice shot of the flower. Stopped down a little, you'd have the whole thing sharp.

[ed2day]

I don't think it's that critical that you be exactly 45 deg. That just affects the calibration numbers on the scale. If you're 5 deg. off, maybe 2 mm is really 2.2 mm(on both sides of zero, i.e. things are still centered). So what? There are things that must be tightly controlled, that's not one of them far as I can see. But using a tripod is critical. And some kind of remote shutter release. The red square is not necessarily where the camera focused. It's where the AF point winds up when the shutter opens--focus is locked when you hear the beep so any movement between them will mislead you. And the fact that you are trying to press the shutter release as soon as you hear the beep makes movement likely.

You might also just try shooting some flat perpindicular surfaces like a brick wall. It won't tell you the degree to which you're misfocused(if you are), but it's just another sanity check and pretty easy. If it's sharp (i.e. cant be made sharper with manual focusing) then your cool.

[willg]

it's just another sanity check


yeah i pretty much lack sanity when it comes to stuff like this...i need to just shoot and be happy...
here is an example..i think i have a good lens
at full zoom and wide open handheld..no post processing other than cropping\
100%
http://uploads.jzl.us/files/fullframe_crop.jpg

and to see the full frame:
http://uploads.jzl.us/files/fullframe.jpg

[lancea]

This is an interesting thread - but I presume the "naughty naughty" icons have been put there by a moderator to replace embedded images that were too large. Any chance of updating your postings with links to the shots? Thanks.

[tim]

Nah they're hotlink protection lancea - right click, view image, reload and you'll see them. They look sharp enough to me.

[lancea]

Hmm. That doesn't work for me. I've tried IE 6, Firefox and Opera 8. Not a sausage. The only way I can see the image is if I view the page source and get the URL from it. From my 5 minute mastering of hotlink protection ;), it appears that it's all done on the target web-site. So funny how it's not working just for me. There are a few other threads showing people having trouble, but they seem to have been fixed by the poster allowing the photography-on-the-net domain.

[tim]

Hotlink protection is done on the target server using the referrer URL. My sites are all hotlink protected, excepting specific directories which i've unprotected so I can post pics here easily.

To get around it in firefox:
1) Right click on image, copy image location, paste into a new browser.
2) Right click on image, view image, hit reload.

If they don't work... bad luck :p

[lancea]

Thanks for that. Doesn't work in Opera and even a multi-step process in Firefox. That'd drive me nuts! One way to keep people from linking I suppose ...

[gcogger]

You're not the only one - I can't get to the images either...

[lancea]

Thanks gcogger. It's never a good feeling when you think you're the only one! All I can say is that "hotlink protection" works very well ;)

[PhotosGuy]

But using a tripod is critical. And some kind of remote shutter release. Or you could just prop the cam in place & use the self-timer to trip the shutter?