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Old Jul 15, 2006, 12:16 AM   #1
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Forgive me - I've only shot with the Rebel XT 18-55mm kit lense prior to this.

I went down to my local camera shop and tested a Canon EF 100-400mm f/4.5-5.6L IS USM lense.

Below are several 100% crops (no post-processing...cropped in Photoshop then saved at 75% quality) from images taken:




Now my question...are these images considered sharp? To me they seem fuzzy...I want to know if I'm simply expecting too much from technology (i.e. expecting a clear, sharp image from an L lense is out of the question) and need to lighten up on my expectations.

Afterthought: All these images were shot at wide open (anywhere from f/4.5 to 5.6) so I guess if I wanted the lense at its sharpest, I could've stopped it down a little bit.
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Old Jul 15, 2006, 3:25 AM   #2
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These show a pretty good lens to me. The fuzziness is due to the nature of your camera.
Sharpness depends on the viewer and how closely you are looking at your picture. If you look at the exact pixels (as you have here with the 100% crops) they will never look sharp out of a dslr. This is because the sensor 'invents' the pixels by interpolating the results of nearby pixels. Each sensor element (photosite) is one colour only and the sensetivities for each colour are different so there are not equal numbers of red, green and blue photosites.
You can increase the apparent sharpness of these images by using the digital equivalent of an unsharp mask which enhances edges and looks to human eyes to be sharper. In fact, this is a destructive process that REMOVES information from the image. Dslrs generally by default do not sharpen their images so as to leave the sharpening process fully in the control of the photographer.
Sharpness also depends on how closely you look at your pics. Look at these at 300dpi and they will appear much sharper. For this reason you should resize your image to the final size and pixel density before you apply any sharpening as the amount you need will depend on these factors.
These crops look very good to me. There is a lot of detail visible. Some unsharp mask will make this a lot clearer.
The purple fringing is much harder to fix, though it looks pretty well controlled in this lens given the first two shots are near a worst case for fringing and it's not too obvious even at 100%.
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Old Jul 15, 2006, 6:11 AM   #3
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Were the images taken hand held or taken with a tripod? Even with IS you have to hold the lens pretty steady to get the best results. Remember you have to consider the 1.6 multiplier effect and if you shooting with an XT without a battery grip the lack of balance willmake it harderto hold steady. I actually got sharper hand held photos with my new Sigma 100 - 300 F4 compared to my old 75 - 300 IS lens because of the extra weight (using 20D w battery grip) although this was for the early shots, later the weight became a big issue. I tend to shoot without bracing against anything. If you get the lens you will get better as you get used to it.

I also agree with the previous poster that these aren't too bad for a 100% crop and no sharpening.

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Old Jul 15, 2006, 6:52 PM   #4
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Try a 300mm or 400mm L prime on a tripod. You may not want the zoom.
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Old Jul 16, 2006, 2:00 PM   #5
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these aren't nearly as sharp as i'd expect from a $1400 lens, nor as sharp as what i routinely get with my $1000 Sigma EX 80-400. some of the softnessis likely due to shooting wide open, and you didn't say what shutter speed you were using, but even with IS, you need to shoot at a reasonably fast shutter speed for a really sharp photo. which AF point and mode you use can also make a difference.

DSLR sensors do not, as was mentioned earlier, "invent" pixels. that can be done in PP, but the image that comes from the camera contains what the sensor "sees", nothing more, except in the case of some really cheap-o cameras advertised as 8 or 10 or 12 mp for under $100. read the fine print on those, and you see it's a 4 or 5 or 6mp sensor, with internal interpolation. the Rebel XT does not do this.
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Old Jul 16, 2006, 7:53 PM   #6
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Here are two images from the same photo. One is a 100% crop taken from the raw file with 0% sharpness applied. The full image was take from the same raw file with sharpness at 25 and additional unsharpen maskapplied in regular PhotoShop.

The picture is @300mm with a 1.4 teleconverter, hand held. The lenses are the Sigma 100-300 F4 and 1.4 teleconverter combination on a 20d. This is my second week with this lens.
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Old Jul 16, 2006, 8:03 PM   #7
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-> Both Sigma (80-400 OS & 100-300 with 1.4x TC) outscore the 100-400L in sharpness!

Actually the Nikon 80-400 VR too:
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Old Jul 16, 2006, 8:13 PM   #8
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I forgot to mention the lens was wide open at 5.6 (with teleconverter) 1/600 ISO 800
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Old Jul 17, 2006, 7:19 AM   #9
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The images are definitely soft, but that, in and of itself doesn't mean much.

First, one critical missing piece of information is what was the camera focusing on? At 5.6 and 400mm you're not going to have a huge DOF - which brings up the next point

Second, what was the distance to the subject? Once you get to focusing at infinity any lens is going to suffer. At those distances it's an issue with auto focus - manual focus may be necessary - depending on the subject.

And, as others mentioned - we don't know how good your hand-holding technique is.

So, before stating the 100-400 performed poorly, it could very well be the test or test execution that's flawed. Which means, even the Sigma lens being touted could have resulted in the same soft image.

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Old Jul 17, 2006, 12:48 PM   #10
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What is the quality of the teleconverter?You introduced extra glass between the lens and the sensor.

The lens looks pretty good considering the use of a teleconverter.

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