Would a Centering issue cause both Front and Back focus in the same image?

Just curious... I ran across an image where...im really sure i have apparently front and back focus in the image..

Will post it in a bit, looking to see if i have anymore...

That is wierd.

First off, Lets go over a few things, Had this lens for a while now, Its always had a slightly iffy problem with focusing in good light, or with light colored subjects.. Oddly enough it works great in low light, Just if i try to use it in daylight the focus tends to not work correctly

It also never is consistent, Some images show front focus, Some show backfocus, Distance and etc dont seem to make any difference

Anytime I try the old "Test chart" crap it tests out perfectly fine...

I have no problems with any other lenses, Either lenses I've owned, or lenses I currently own I'm confident enough to say its not my technique and its not my 7D

I was just reviewing a few shots I did from today, and im pretty sure (To my eyes at least) it appears the lens is both front focusing and backfocusing) I also went back through some others... In general i am also just going to post up a bunch to show that the issue is inconsistent...not a simple MA is going to fix it...

Also I've shot thousands of images with the lens, Multiple subjects, and its cropped up on more subjects than just these... I just tend to not keep ones that are not "Right"

No adjustments on these, except for a slight output sharpen from LR3, No exposure adjustments (Yes they need that, I'm well aware guys) Only one seems to show the weird simultaneous front/back focus issue...but its the only image i have thats taken in such a situation to make such a thing easily evident

Lets start here:

The only lens I have that can give me these same kinds of head scratchers is the Canon 24-70L. That lens as a seriously curved 'plane' of focus. The curvature can lead to some real strange effects regarding what is and what is not in focus.

I dunno, Now im trying to figure out if i have more focus problems with a certain orientation or something...

I know the lens makes an odd noise when focusing (Not the usual HSM sorta "swooosh" its more..high pitched and less swooshy?)

Kenji,

My take on your simultaneous front/back focused photo:

You didn't take this photo completely perpendicular to the aisle. You may have been standing in the center of the aisle, but you're still shooting at an angle, which allows you to capture the right side of the aisle (with the products hanging), but we don't see the left side of the aisle. In other words, see attached image.

Your plane of focus (while backfocusing in relation to the dog's head/face) fell on the dog's butt and the treats on the right side.

^- possible i admit...

Still not perfect in terms of AF accuracy dealing with light subjects and subjects in better lighting though...definitely needs to go to sigma i think

Kenji:

I think Julian almost has it correct. I think your perspective is off. Actually, the treats you think are in front of the dog appear to be slightly behind him in the photo. If you look at the full picture (dog facing towards you) the "Rawhide Chips bag" appears to be the most in focus. If you draw a line from that bag down to the bottom shelf the red vertical rail (second from front) appears to be the one in focus and slightly behind the rawhide bag. And, it appears to be almost even with the back leg of the cart. Thus, your dog's rear which is closer to the back of the cart is the point of focus.

damn slight optical illusions then

Ok so i guess at least theres no centering issue...

Its still not focused on what i want it to focus on however >.>

I concur.. throw it on your tripod, make sure your plane of focus is flush. If not, then sent her in.

1Tanker wrote in post #13972008
I concur.. throw it on your tripod, make sure your plane of focus is flush. If not, then sent her in.

-edit- Yay for not reading, I guess I can go find and dig out the tripod... Keep in mind none of my walls are flush though

KenjiS wrote in post #13972088
-edit- Yay for not reading, I guess I can go find and dig out the tripod... Keep in mind none of my walls are flush though

Sorry if this was already mentioned; i'm not having a good day, and starting to "drown my sorrows", if you get my drift.

1Tanker wrote in post #13972127
Sorry if this was already mentioned; i'm not having a good day, and starting to "drown my sorrows", if you get my drift.

Aw man im sorry

Maybe this will help:

IMAGE LINK: http://www.flickr.com …unetsukiphoto/6​786519516/

An orange? Seriously?

KenjiS wrote in post #13968431
^- possible i admit...

Still not perfect in terms of AF accuracy dealing with light subjects and subjects in better lighting though...definitely needs to go to sigma i think

ahaa! makes sense now .

ed rader