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Old Oct 5, 2003, 5:35 PM   #1
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Default Sigma 70-200 EX Lens

Hello Everyone,

Well I have had my Sigma 70-200 for a few weeks now. It seems to preform well. But does anyone notice that more often then not. The pictures turn out soft? Actually so soft that either I think its out of focus or like if one of those sticky plastic wrappers are covering a lens (Kinda like the PDA protector screens). Sometimes it can be pretty sharp. But I havent been overly pleased with the final product. I am actually more pleased with my Canon 75-300 IS. That has produced numorious fantastic pictures. With this lens it tends to be a shock to get one that looks great... :?

Anyone else with similar problems? Should I change up to a Canon L Series and leave these EX Sigma's alone? Or do you think I might have a bogus lens? It could also be the user ops:

Should I try this lens in full auto mode? Instead of having it shoot in f2.8 most of the time? Could that be the reason to unsharp photographs? (ie: birds and closeups) Should I just use the 2.8 for distance and slow moving objects?

Maybe Im totally missing something here that I dont know about.
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Old Oct 5, 2003, 7:24 PM   #2
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Well ran a small test in my kitchen. Lighting was above normal lighting conditions. Here we go.

Subject: Medicine Bottle
Distance: 10ft appox.
Focal Range: 200mm
Photo: Image at 100% size and then cropped.
Other then that, unaltered.

Sigma EX 70-200mm f/2.8 vs. Canon EF 75-300mm IS USM

Sigma photograph will be listed first then canon in this test.

Sigma vs. Canon @ ISO400





Sigma vs. Canon @ ISO800





Sigma vs. Canon @ ISO800 w/ Flash





Obviously there is a considerable difference between the two. I have no idea what is going on here. Can anyone help? Or is it just a quality issue? Maybe I should stick with canon items? Or is there a test that can really show the actual pro's and cons vs another lens? All help would be appreciated.
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Old Oct 5, 2003, 7:41 PM   #3
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Default Whoa, both look fuzzy.

Russell,
Both look a bit blurry from here.... Did you use a tripod to remove the hand shake possibilities? Did you turn off IS (assuming you were on a tripod it should be on the "O" for off)? What were the final settings (f-stop/shutter speeds) you used for the shots? If they were equal, I would have hoped for closer results.

I don't have that Sigma, but the numbers suggest it is pretty good. And being a faster (F2.8 ) lens, I would think it would do fairly well in an indoor test.

One thing to remember on you closeup/tele shots outside, that F2.8 is going to make for very little DOF to get the right things in focus, but when you shut it down a bit to say F4 or more, you should be getting sharper images than this.

Have you tried cleaning the lens (both ends)? It almost looks like those shots where people smear vasoline on the lens to give a "softer" look to models.... (when they ain't all that great looking!!)

Hang on though, I'm sure when people see this post in the morning, they'll give you some good answers.

Jody
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Old Oct 5, 2003, 8:06 PM   #4
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Default One more thing

Russell,
After mentioning "clean lens" I decided to look through the one sitting on my table (28-135). Ick!!! Even worse, when I held it up and pointed it at a light, I saw a very dead ant inside. Of course it wouldn't have shown up on a photo ever, but I had to get it off the lens inside. I few good extend/contracts, and a shake or two, he fell down inside somewhere (I hope!!!)
I then used some lens wipes on the the outside, and the light became a bit clearer.... Gee maybe my shots will be sharper now too...

Jody
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Old Oct 5, 2003, 9:23 PM   #5
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Well, cleaned the lenses front and back. And tried shooting both lenses set at f/4.5 at different iso's. Drastic difference with the Sigma. Take a peak.

Old shot vs New shot from Sigma Lens (Note its blurry from movement.) However the halo'ing has deminished.

Sigma @ ISO400 - Old vs New




Sigma @ ISO800 - Old vs New





Sigma with flash (First image was at 800ISO, then my second was the second time around but at 400ISO)






But I notice a large improvement from f/2.8 and cleaning the back of the lens (which was never cleaned since removed from the box) but Ive only had it for a few weeks. Should I expect this much improvement from going from f/2.8 to f/4.5 and cleaning it?
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Old Oct 5, 2003, 10:55 PM   #6
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Quote:
Should I expect this much improvement from going from f/2.8 to f/4.5 and cleaning it?
You should... You've just increased the DOF of the Sigma to match that of the Canon (especially on a curvature) you know what they say about comparing apples vs oranges! :lol:
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Old Oct 6, 2003, 12:11 AM   #7
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Seems like all shots, except the last one with the flash, had focus problems. Probably the AF didn't have enough light, or you combination of camera and lens either front or back focusses.

Barthold
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Old Oct 6, 2003, 7:40 AM   #8
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Ill post some more examples of the problems I had yesterday. The thing is, isnt SLR (What you see is what you get?). I swear almost all of my photographs where crystal clear when I took them. Most shot around 1/2000th or so. But maybe it was my fault forcing it to constantly shoot in f/2.8? Maybe I should have just let the camera go on auto pilot. Im sure it knows whats best for most shots... :?
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Old Oct 6, 2003, 8:46 AM   #9
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Russell

I did this DOF test a while back. If you stopped the lens down to the f/4.5 working aperture of the other lens the 'perceived' sharpness also increase... Of course if you close the other lens down it's sharpeness also increases but to the expense of even less light!
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Old Oct 7, 2003, 1:47 PM   #10
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Doing a lens test like what you did is very hard. I am no expert, but I've read a few things about doing it Here are some things to worry about.

Use exactly the same settings. This means (of course) picking settings that both lenses can do. This isn't fair to the lens with the smaller max fstop (in this case, the Canon) because stopping down a lens a bit should improve its sharpness. There is nothing you can really do about this. Just realize it and account for it in your conclusions.

Use all the long lens technique you can. This includes: mirror lockup, remote control or timer, a beanbag above the tripod mound.

Make sure you have LOTS of light.

Don't use a curved subject use a flat subject. Better yet, use a lens test chart.

Use manual focus. The AF in the 10D isn't good enough (it is technically legal to have the front edge of that bottle be in focus, but not the rest of it.)

Mark the tripod leg points on the floor. Lock the tripod legs and height. Make sure the camera is at exactly the same location in 3D in relation to the subject.

[my addition]Don't do the test in the kitchen. When the compressor turns on in your fridge, it will shake everything on the floor, including the camera. If you have to do it there then unplug the fridge.

It also wouldn't hurt to use a subject which has some color on it. Not in the center, but that will still be in the picture. Some lenses alter/shift color slightly. You'll want to know this.

And Iím sure there is more you should do (that I don't know.)

Eric
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