Back/Front focus Issues

sep9001

sep9001

Messages
5,627
Name
Kev
Edit My Images
Yes
Hi

I have a lens which I think has a front/back focus issue and want to know if the issue will be the same at all focal lengths or just at certain ones? For example I can see the issue at 28mm, however at 75mm it looks okay.

It is probably me doing the test incorrectly but just want to check before I do more tests.

1. f2.8 at 28mm, the middle focus point was on the AAA battery in the middle.

DSC_0002-2.jpg

2. f2.8 at 75mm same focus as above.

DSC_0004-2.jpg


Thank you

Kev
 
Have you tried fine tuning the focus at 28mm? I believe that the focus issue can vary at different focal lengths.
Did you use a tripod during the tests?
 
There's a lot of variables with this test so obviously I can't be sure that you've done it right. However it does look as though it's back focussing a touch at 28mm, although you should have slightly more in focus behind than in front.

It's always difficult with zooms as they can front focus at one end and back compromise at the other, so unless you have one of the Canons that can make adjustments at both ends it's always a compromise. I always adjust mine so that they're right at the long end as at longer focal lengths front/back focus is more apparent due to the smaller depth of field.
 
Thank you both. Yes I used a tripod and it was on timer.

I currently have a D90 which does not have the focus adjustment. Need to decide if I send it off to Tamron to sort out or keep it until I upgrade my D90 and see how I get on.
 
Tough call as it looks OK at 75mm, not sure if they can adjust one end without effecting the other. Might be worth contacting them and asking?
 
I have a tamron 70-300 vc usd and I was convinced that the focus was off, but it was inconsistent and in the end I thought it was me that was the issue.
I tried adjusting the focus on my D7000 and thought I'd nailed it, then more issues etc.
It was doing my nut in. I recently purchased another d7000 on here, and bingo! Massive improvement and I have way more keepers than before.
Yet with my other lenses, my old D7000 was fine.
 
Thank you, I had emailed them and they have said I need to send it in for them to check before they can give me a price.

Just worried on the cost and if it is worth getting it fixed.
 
sep9001 said:
Thank you, I had emailed them and they have said I need to send it in for them to check before they can give me a price.

Just worried on the cost and if it is worth getting it fixed.
Click to expand...
Yes but surely they can tell you whether they can adjust one end without effecting the other?
 
snerkler said:
Yes but surely they can tell you whether they can adjust one end without effecting the other?
Click to expand...
I need to look into it further. The estimate is free it would cost postage there and back, might just have to send it off and see. I presume if it is too expensive I can sell the lens off a spares only.

Thank you
 
OldCarlos said:
TBH both body AND lens need sending together if they are tuning for best results.
Click to expand...

Thanks, may be I should try the lens on my mates D90, if I get the same results then the lens is an issue, if not then body .
 
You must log in or register to reply here.
Back
Top