50L - What do you make out of this?

I went to check out the 50L at a local store and I took a bunch of pictures. It clearly wasn't focusing properly and this here is the sales person. Look at this image, it is front focusing but it seems like it is also back focusing - his cheek which is behind the focus point and his hair which is in front of the focus point have some detail in them but the focus point which was his left eye is OOF. This is at f/2.2.

I loved everything about this lens by the way. I looked at all images and the areas that were in focus had plenty of detail for my taste, I didn't think it was soft wide open and then the colors and the MFD really did it for me.

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Focus shift. f/2.2 is right in the range for this to happen. The 50L i had exhibited it from f/2 to f/4.

So that's what focus shift is? It moves on a different axis? I can't quite comprehend how it is possible to have back and front focusing problem. That sucks ...

pixel_junkie wrote in post #11874592
So that's what focus shift is? It moves on a different axis? I can't quite comprehend how it is possible to have back and front focusing problem. That sucks ...

The 50L has focus shift from ~f/2-f/4 at close distances. It is caused by the curvature of the plane of focus. It happens because the lens focuses wide open, the lens stops down as the shutter clicks, the curvature of the focus plane shifts. So technically speaking, it focuses accurately to start, but stopping the lens down moves the plane of focus.

Here some articles I was just reading last night about focus shift with the 50L:

http://www.ronscheffle​r.com/blog/?page_id=37​0
https://www.lensrental​s.com …with-wide-aperture-lenses


I did my best to explain it

You probably didn't get a chance to do MA to the lens? I'm guessing probably not being you were at the store and all... ??

Well my 50L focuses accurately most all the time. I mind you, I had to do a -13 MA adjustment though.

But after the MA, I don't really get this "focus shift" everyone talks about. Here is a shoot I did with my 50L. Most shots are at 2.0 or 2.2... the very last photo is f1.6

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^

Jessica Alba!

m.shalaby wrote in post #11875701
But after the MA, I don't really get this "focus shift" everyone talks about. Here is a shoot I did with my 50L. Most shots are at 2.0 or 2.2... the very last photo is f1.6

Staszek wrote in post #11874672
The 50L has focus shift from ~f/2-f/4 at close distances.

You're not in that F-range.

Are those shots at MFD? I can't tell...

Beautiful stranger though!!!

I have mine MA at +5 and there is very little difference now in terms of sharpness from f1.2 -1.6 (i.e. it's sharp enough) With regard to the focus shift luckily mine shift's very little. It may have to do with better Canon QC in the newer samples.

What's interesting though is that ever since getting the ST-E2 the focus is really spot on in any apertures and in most AF point (except the most outermost laterals- i think this has to do with field curvature wide open)

pixel_junkie wrote in post #11874536
I went to check out the 50L at a local store and I took a bunch of pictures. It clearly wasn't focusing properly and this here is the sales person. Look at this image, it is front focusing but it seems like it is also back focusing - his cheek which is behind the focus point and his hair which is in front of the focus point have some detail in them but the focus point which was his left eye is OOF. This is at f/2.2.

I loved everything about this lens by the way. I looked at all images and the areas that were in focus had plenty of detail for my taste, I didn't think it was soft wide open and then the colors and the MFD really did it for me.

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To my eyes, the image above is back-focused, period. What makes you think the in-focus lock of hair is in front of the eye? Looks to be on the same plane as the in-focus end of his eyebrow behind his eye.

^ You may be right. I just thought there's a lot of detail on the cheek (compared to the focus point, the eye) which would be closer to the camera than the eye is. The front focusing is pretty clear.

pixel_junkie wrote in post #11877622
^ You may be right. I just thought there's a lot of detail on the cheek (compared to the focus point, the eye) which would be closer to the camera than the eye is. The front focusing is pretty clear.

I see what you mean about the cheek, but couldn't this also be the "optical illusion" that a nicely-lit area looks sharper than an under-lit area? I see that while the cheekbone area may be acceptably sharp, it is not completely in focus - farther back on the cheek looks sharper. And the eye is not that out-of-focus - maybe it just seems worse because it is in shadow. Finally, didn't see this guy in person, but my cheekbone is about even with the front of my eye, or at least close enough that a slight downward tilt of my head would bring them in line.

Just some food for thought. I only bring it up because I would hope Canon did not engineer a tilted plane of focus into a non-T/S lens. Just hope - no experience with this lens myself.

Hi, sorry to barge my way into your thread, but could you explain to me what you mean by adjusting the MA (-13 +5) as I have never heard of it before. Back Focus & Front Focus I understand, but Adjusting the MA is lost on me!

HyperYagami wrote in post #11877198
You're not in that F-range.

Yes I am, 2.0 is where it starts, and thats where most of this shoot was done. 2.0 and 2.2

She's not a stranger as well... she's a friend of mine and my wifes. I took a little break from the 100 Strangers project, but should resume in a week or so... as soon as this weather makes it more bearable.