Front/back focus testing distance?

Was wondering when you do test to check for front/back focusing, do you shoot at minimum distance or at a certain distance?

I took a few shots with a recently bought used Tamron 28-75mm @ 2.8 from minimum focus distance the other day and found that at 28mm the lens back focus a little, while at 75mm it's spot on.

Why are you assuming it has issues? Test at the normal distance you will be using it at - nothign else makes sense.

gasrocks wrote in post #11987754
Why are you assuming it has issues? Test at the normal distance you will be using it at - nothign else makes sense.

Don't get me wrong, I love this lens, pictures come out great. Never really thought about testing it until started reading too many posts on here on front/back focusing and one of the way to test for it. I actually like using this lens at the wide end more.

Just shoot at different distances, focusing issues should show themselves if they exist.

as was mentioned, don't stress over testing your lenses unless you actually see a problem in your photos.

for example, I bought a brand-spankin' new Canon 50mm f/1.2 L lens....sounds delicious right?

this is an example of how my photos were turning out. the leaves in front of the focused area are sharp, but not the trunk

Thanks for the responses


PWard wow glad that got fixed for you.

Tamron's warranty is for 4 or 5 years isn't it? if you end up with that lens, you want to check and see whether the warranty is still valid, and if so, send it in for calibration.

PWard wrote in post #11991677
Tamron's warranty is for 4 or 5 years isn't it? if you end up with that lens, you want to check and see whether the warranty is still valid, and if so, send it in for calibration.

Tamron USA has a six year warranty, only for goods which it has imported and distributed...this does not apply to goods purchased outside their distribution territory nor gray market goods. And...

"The Warranty shall not extend to anyone other than the original purchaser of the lens or the person for whom the lens was purchased as a gift. "

PWard wrote in post #11991677
Tamron's warranty is for 4 or 5 years isn't it? if you end up with that lens, you want to check and see whether the warranty is still valid, and if so, send it in for calibration.

I'm the third owner of this lens and didn't come with warranty card.