Originally posted by biz-engineer AF adjustment easy ? You don't have to understand anything.
1) Take one target with fine details, for example a book with some text written small at a distance, or a newspaper, set the lens aperture to maximum (smaller f number).
2) Take one photos with 0 adjust
3) Take another photo with +1 adjust
4) Take another photo with -1 adjust
5) Take another photo with +2 adjust
6) Take another photo with -2 adjust
7) Take another photo with +3 adjust
8) Take another photo with -3 adjust
9) Take another photo with +4 adjust
10) Take another photo with -4 adjust
etc...
Compare images at 100% zoomed, use the setting that give the best image sharpness.
This is more like what I was looking for. Thank you very much.
---------- Post added 25-05-16 at 08:21 ----------
Originally posted by TheOneAndOnlyJH If you want to get an highly accurate focus adjustment, you DO need to go through the hassle. Definitely use a low ISO and tripod to get the clearest, sharpest images you can. High ISO or hand holding the camera can soften the image enough that you won't see the minute focus differences as easily.
That being said, if you're getting consistent front or back focusing in the field, it can't hurt to try some adjustments. Just take multiple shots to confirm. (Don't consider it 'correct' based off of one well focused picture!)
Some lenses also require a different adjustment at different ends of their zoom ranges. I've found that certain lighting situations and subject distances can trick the auto focus too.
I have a K-3 and Tamron 17-50 f/2.8 combo that works great on subjects 5-150 feet away with an adjustment of +1. However, one somewhat dimly lit room of my house with a 'warm white' LED ceiling fixture causes the same combo to front focus, so I have to dial in -3 for subjects from 5-15ft. This is even worse when the subject is within 3ft, and I have to dial in -8 or so. When I first noticed all my pictures were severely front focused I didn't have time to set up a target and go through the whole adjustment process. I roughly adjusted it through about 15 frames of trial and error after which I shot a decent amount of keepers. (Previously I'd had none.) On going back to regular lighting everything was severely back focused until I returned the adjustment to +1 and it works great again.
(Now that I think about it, I'll have to go back and fine tune the settings for that room so I know right where to set it to next time I take pictures there.)
I never thought about the low ISO part, but it does make sense. Thanks.
---------- Post added 25-05-16 at 08:27 ----------
Originally posted by Adam "All the trouble" is a complete must IMO. You're talking about micro-adjustments, after all. To apply the proper corrections and reach a definitive conclusion, a controlled setup is necessary.
If you're not having any issues with your lens, just leave the adjustment setting alone. Unless you're working with a very shallow DOF chances are that a small inaccuracy will have no practical effect.
It seems like the complete must is the general concensus. But the task is daunting for me.
My tamron 28-75 2.8 seem soft for my liking compared to its big brother 70-200 2.8. I am wondering if its front focusing
I just want something simple to test my suspicion.
Thank everyone for the advice.