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Author Topic: Canon 24-70L soft or not (link to samples)?  (Read 4660 times)
Graham Welland
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« on: June 12, 2005, 05:16:12 PM »
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Put it on a tripod and use mirror lock up & cable release to see what your lens is capable of. Handheld with a fast shutter isn't really enough to prove anything as there are so many variables.
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Graham
jseymour
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« Reply #1 on: June 13, 2005, 05:25:42 AM »
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What I'm struggling with is how much change in sharpness is reasonable performance from this lens as the aperture/focal length changes, and as I look in different parts of the frame. Has anyone actually posted 100% crops of their "brick wall test" with a good 24-70L that I could use as a comparison?

J
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jseymour
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« Reply #2 on: June 13, 2005, 08:51:00 AM »
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Indeed.

I was just trying set a benchmark with other 24-70 copies, not even a prime that's supposed to be a little better. I'm just having difficultly getting even a subjective impression of what general 24-70 sharpness performance is like, wide open, edge of frame, @ 24mm...

John
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jseymour
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« Reply #3 on: June 13, 2005, 09:59:43 AM »
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Quote
Quit obsessing and go shoot photos.
I know, I know...

All that really triggered this was getting a reminder my warranty expires soon  Sad
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jseymour
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« Reply #4 on: June 12, 2005, 05:45:45 AM »
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I've seen http://www.luminous-landscape.com/reviews/...70-review.shtml

and I'm not sure if what I'm seeing on my copy is typical or not...

I took these

http://camera.fotopic.net/c574855.html

Technique was to set centre focus point on the building (should have been near enough infinity in these cases, I think), focus lock (half press shutter in one shot focus mode) and recompose to get the building "target" in a different part of the frame. All reasonably fast shutter speeds, hand held.

All jpg, parameter 2, Av, AWB. You can look at the original. I've only renamed the files (no cropping, resaving, or anything else).

So trying to take a step away from the theory of how good L glass is supposed to be, and pixel peeping, if YOU have one of these lenses, is the lens I have showing typical performance, given the technique, do you think?

I know no lens is perfect. I know taking this kind of shot at f2.8 isn't what I should be doing other than as a test. I'm just trying to work out if my copy is typical or not. I don't expect perfection. But these lenses are not cheap, and I want to work out if this is as good as it gets, typically.

I've seen suggestions I should be taking pictures of newsprint, camera on tripod, mirror locked up etc, but even if I did that, I've know idea what I should be seeing as acceptable.

John
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eatstickyrice
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« Reply #5 on: June 12, 2005, 10:56:49 PM »
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John, I recommend you do a "brick wall test". What you would do is put your camera on a tripod, and then either use the camera's self timer or a cable release to take the photos. Doing so reduces the chances of any movement from tripod shake. In this case, take photos of the brick wall at 24, 35, 50 and 70, and at f 2.8 and f8 for each of these. Afterward you should open them up in Canon's software to verfiy where your specific focus point was. If the lens is in good shape, you shouldn't notice any softness at any of the focal lengths, though the 24-70 is sharper at 24, than at 70. The 24-70 should give you lots of detail, but you will notice more detail at f8, than at f2.8. After looking at the photos in Canon's software, open them up in Photoshop or a similar program and zoom to 100%, 200% and 400%. The sharpness will decrease as you zoom, which is perfectly normal, so long as you could detect sharpeness at 100%.

Some things to consider when evaluating your lens:
1. Shooting a white subject is likely to not give you the best focus a lens is capable of. Look for something more neutral like grey (or the bricks on a wall!)
2. If it is windy on the day you want to take your brick wall test, you need to wait for a different day. Even if you set your camera on a high-end tripod, you can watch the camera shake as the wind blows.
3. If you aren't familiar with how to read MTF charts, check out Michael's tutorial on how to do so. If necessary, you can search luminous-landscape to find the tutorial.

Happy shooting!
Rick
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Ray
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« Reply #6 on: June 13, 2005, 08:31:19 AM »
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Lens tests are meaningful only in relation to other lenses or in relation to a defined standard such as MTF and line pairs per mm.

It would be difficult for anyone to comment on whether your jpegs are typical of this lens; whether they are average, below average or above average.

If you are not sure if your 24-70 is up to scratch, I suggest you compare it with some primes that fall within its range of focal lengths; for example the 24/2.8 or the excellent value and inexpensive Canon 50/1.8 ll. You would expect the primes to be marginally better. If they are no more than very slightly better, you can be fairly confident you have a good copy of the 24-70.
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Jonathan Wienke
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« Reply #7 on: June 13, 2005, 09:45:30 AM »
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I think what you're seeing is well within reasonable for a 24-70 wide open at 24mm. Overall good sharpness and contrast with just a hint of CA that cleans up well in Camera RAW or PSCS' lens correction tool. Quit obsessing and go shoot photos.
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Graham Welland
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« Reply #8 on: June 13, 2005, 04:50:14 PM »
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I checked the EXIF data and see that you are using a 20D with the 24-70L. I've found that this camera needs a fairly robust amount of sharpening to get the best from images. I was fretting about my adoption of canon digital and lenses until I realized that this is 'normal'.

I have the 10-22 EFS, 17-40L, 24-70L and 70-300 DO lenses and they all benefit from extra sharpening in PS with this camera. Do this and the results are excellent.

With my D1X and Nikon glass I didn't need to sharpen as aggressively to get the same acceptable results. I won't mention my Mamiya 645AFD/Kodak combo which, sorry folks, by comparison still makes these lenses seem like coke bottle bottoms before sharpening - oops, I did!  Cheesy
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Graham
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