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Old Dec 13, 2006, 2:01 AM   #1
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I test my lens this evening, the first test set to 50mm f5.6 1/125 ISO-100 Sunpak PZ-5000, hand held. Please share your thought, thanks.

Len=Minolta 50mm f1.7


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Old Dec 13, 2006, 2:03 AM   #2
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Minolta Kit len 18-70mm f/3.5 - 5.6


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Old Dec 13, 2006, 2:05 AM   #3
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Minolta 28-75mm f/2.8


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Old Dec 13, 2006, 2:07 AM   #4
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Sigma 28-200mm f/3.5-5.6


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Old Dec 13, 2006, 10:58 AM   #5
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lsifs wrote:
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I test my lens this evening, the first test set to 50mm f5.6 1/125 ISO-100 Sunpak PZ-5000, hand held. Please share your thought, thanks.

Len=Minolta 50mm f1.7

While I do see some subtle differnces they are very similiar. The text is slightlyt sharper on the 28-75, but it is hard to tell if it just happened to focus lock betteror if the slightsharperness advantageis because of the glass quality. The reds of theSigma don't seem as saturated but not by much.

The results might vary more on a closeup shot of a person or other object we we can examine the detail better. Alsoby using a flash the playing field isequalized so we can't really compare the lenses low light capablities, which is where the 50 1.7 and the 28-75 2.8 would certainly shine. It all depends on what you are trying to illustrate in your comparisons.

If we compare the photos and ignore the conditions, it showsthat the kit lens can certainly competewitha prime or brighter lens. In ambient light, the brighter lenses will be able to utilize faster shutter speeds and lower ISO settings, which can dramatically affect our photo oppourtunities and the quality of our photos.

Thanks for sharing
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Old Dec 13, 2006, 12:36 PM   #6
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Thanks for your comments, I will do more tests in low light when I have time.
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Old Dec 15, 2006, 2:18 PM   #7
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I just compare the minolta 28-75mm f2.8, minolta 50mm f1.7 and the sigma 28-200mm f3.5-5.6 on my KM5D, theselensset at 50mmf5.6, aperture priority, the camera calucated the ligh anddetermined theshutter speed of 1/20" onboth Minolta lens and1/13" on the Sigma len, these make the picturesfrom the minolta lens a little too dark (underexposure) but the picture from sigma len is perfect good, I don't know why the KM5D did not detect the lightcorrectly on every len? But when I use the M mode to set all lens at f5.6 and 1/13", the picturefromeach lens are the same. Is it the len make the difference or the camera? Looks likethe sigma has done a better job than the minolta. Anyone has the same experience? Any solution?
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Old Dec 15, 2006, 2:35 PM   #8
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It's not uncommon to see some variations in metering between lenses.

But, how controlled were your conditions?

For more accurate testing, you'd need to make sure the focal length and framing were both identical (since you may have brighter areas or darker areas in the frame the metering is looking at if they were not), focus point was identical (since the camera's metering is going to weight the active/selected focus point more, even with matrix, so make sure you're selecting it versus the camera), lighting was identical (it can change between shots), and even white balance was set the same way using a preset (since you can have lens coatings differences that influence it). If you were not using a tripod, that can impact results, too.

Of course, if you were using a flash (as you were in your last test), that's really going to mess everything up (since even the physical characteristics of a lens can impact the amount of reflected light being seen from the metering preflash), as well as flash mode and lens type (non-ADI versus TTL). I would not use flash photos for comparing lens quality.

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