Scoop! 50L Pic IN Focus

wow all this just went over my head. whats next? nuclear fission theory

Fusion is the next nuclear craze!

wimg wrote in post #3621487
And the most important question of all, of course: what was the focusing distance?

Kind regards, Wim

That was about 4' wim. Is that too far away? I thought you were having problems in the 3'-6' range?

Steiglitz wrote in post #3621518
These are near useless, as the center part of the images have little or no contrast, making it very difficult to determine back/front focusing issues.

Try again, but place the center FP on a higher contrast object so that we can better determine if the lens is right on, or backfocuses.

My own 50L has a very bad BF issue, and if I used it to take the shots you did, this issue would not really show....

Bollocks. There's more than enough contrast in there. Look at the crop and you'll see a gradual reduction in focus, fore and aft, along the tool holder on the left hand side. Not sure what you shoot/work with, but DOF is around an inch here, which I think is a fair test of any lens. It's only your own belief system that won't allow you to accept that there is nothing wrong with this lens. As for the three you have owned, are you sure you weren't given the same one three times?

With my 50L the problem is worse at about 3 feet and f/2.8. Also with mine the shift is just enough to put the focus plane at the extreme front of the DOF. While it is a bit hard to tell in the sample you posted it doesn't appear to exhibit the focus shift commonly discussed. Do you have any other sample shots. If there are good copies of the lens out there I'd like to gather enough evidence to prove to Canon that my lens is defective.

Here's my a 100% crop of my lens at f/2.8 and three feet (vertical line across text at bottom is in the focus plane, each tick mark is 2mm).

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bildeb0rg wrote in post #3624412
That was about 4' wim. Is that too far away? I thought you were having problems in the 3'-6' range?

Anything less than 4-5 ft, at F/1.2 - F/2.8, which is why I was asking.

I will try another copy sooner rather than later, but am currently on leave, read: doing major house maintenance, so too stuffed right now to do anything but read here a bit, occasionally .

Kind regards, Wim

So it's under 4' your getting a shift? O'k. I'll try it at less than that. Is it wide open to 2.8 you need?

bildeb0rg wrote in post #3626067
So it's under 4' your getting a shift? O'k. I'll try it at less than that. Is it wide open to 2.8 you need?

If you would, yes please.

I already know there are 50Ls out there that focus properly under those conditions, but the 3 I had didn't...

Kind regards, Wim

P.S.: I know I am asking a lot, but could you maybe try low, medium and high contrast shots? I had the problems with low and high contrast shots, much less so with medium contrast.

What I tried, amongst others, to give you an impression:
Low contrast: portraits in low light, partial face only
Medium contrast: colourful tartan blanket in average (day)light
High contrast: edge of metal object, illuminated by halogen light, with part of halogen light in image, and very dark shadows around illuminated metal parts.

Tom W wrote in post #3622390
I'm not in favor of the 45-degree angled target due to the fact that the AF sensors on the non-1-series cameras are considerably larger than the indicators in the viewfinder. The AF sensor can easily lock focus anywhere on the area it covers.

This 10D AF picture superimposed over a ruler illustrates this point:

In this case, if the left side of the AF sensor detects focus, it will appear to front focus, whereas if the right side of the AF sensor detects, it will appear that the lens is backfocusing. I prefer a flat target, with an angled scale or other array to show depth.

Sorry about the slide-rule. Apparently, it was the only ruler I had available at the time.

You may rememebr this one Tom, but many reading may not,
This thread shows how to get the best solution form the 45* angle test, by NOT focusing on the text...
https://photography-on-the.net/forum/showthre​ad.php?t=10526

I just went through this in setting "AF Micro Adjustment" for the MkIII on two lenses,.
When I shot the paper chart @ 45* (or so) the results were all over the place, usually behind the dark line..

When I put solid 3D object in line with the center mark and focused on, I got spot on perfect consistent results with both lenses.

wimg wrote in post #3626153
I already know there are 50Ls out there that focus properly under those conditions,

I would believe that only if I were to see some evidence to that effect, i.e., focus test charts or equivalent.
The backfocus phenomenon has been too commonly observed, too repeatable for it to be a random QC or "bad batch" problem.

CyberDyneSystems wrote in post #3626177
You may rememebr this one Tom, but many reading may not,
This thread shows how to get the best solution form the 45* angle test, by NOT focusing on the text...
https://photography-on-the.net/forum/showthre​ad.php?t=10526

I just went through this in setting "AF Micro Adjustment" for the MkIII on two lenses,.
When I shot the paper chart @ 45* (or so) the results were all over the place, usually behind the dark line..

When I put solid 3D object in line with the center mark and focused on, I got spot on perfect consistent results with both lenses.

I DO remember that thread, and I remember using that technique with my 10D to check focus. I aligned a golf tee with the "0" mark on my scale and focused on the tee instead of the chart. I couldn't remember where I had read about it - I just remembered doing it.

BTW, the 10D and 50/1.4 were right on the mark if I recall correctly.

Hey Wim, you owe my niece a gallon of ice cream. She hates getting her pic taken. Both at less than 3 feet, centre point and f2.8. Focus is on the eye ball.

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And one for child line U.K....She doesn't have a pony, you know.

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bildeb0rg wrote in post #3630085
Hey Wim, you owe my niece a gallon of ice cream. She hates getting her pic taken. Both at less than 3 feet, centre point and f2.8. Focus is on the eye ball.

Ok, thanks! Where do I send the ice cream to?

Anyway, looks like it is possible indeed!

Kind regards, Wim

bildeb0rg wrote in post #3630106
And one for child line U.K....She doesn't have a pony, you know.

Did you do one at F/1.2, too?

Kind regards, Wim