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#1
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How do I test and compare lenses
Hello,
Yesterday, after a long wait (US to India by regular mail), I received my M42-to-EOS adapter that I had ordered for $12.95 from eBay. I immiediately set upon comparing the kit lens (Canon 18-55mm) with the Pentax Super Takumar 50mm f/1.4 on my Canon 300D. First, I mounted the camera on a tripod, secured all the screws, set the camera to "M" mode and went about shooting a fixed subject indoors. Once I set the focus, all I did was change aperture values for each successive test shot to compare the difference between various f-stops of the lens. I also used timer and MLU. The images at 1.4 are horribly unsharp. Sharpness started picking up at f4, was best at f5.6-f10 and was reasonable at f16. I compared the kit lens at 50mm f/5.6 to the Pentax 50mm at f/5.6. Results were not very different. But somehow the horrible unsharpness at f/1.4 and the little difference in results between the kit lens and the Pentax 50mm left me thinking if I've been doing something wrong in the testing. Other than that the Pentax's focussing ring is damn smooth. Once I went back to the kit lens I was *shocked* by the jerky and wobbly focus ring. Metering wasn't tough either with the Pentax. In "M" mode, I just made sure than the adjustments to the shutter speed kept the exposure indicator at "0". Suggestions/pointers appreciated. - Siddhartha |
#2
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Isn't there a mount to be removed from some lenses before it is fixed to the
adaptor? I'm not suggesting that you immediately start dismantling your lens, but I seem remember having to do that once a long time ago with an M42 screw lens on a Russian camera, NOT a Pentax. |
#3
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teflon wrote:
Isn't there a mount to be removed from some lenses before it is fixed to the adaptor? I'm not suggesting that you immediately start dismantling your lens, but I seem remember having to do that once a long time ago with an M42 screw lens on a Russian camera, NOT a Pentax. No, I didn't have to remove any part of the Pentax lens to make it fit the M42-to-EOS adaptor. Although, I have also read about ring adaptors that require part of the screw mount lens to removed before use but haven't come across one. I will also receive two more M42 lens sometime this month so will confirm their usage as well. - Siddhartha |
#4
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"teflon" wrote in message ... Isn't there a mount to be removed from some lenses before it is fixed to the adaptor? I'm not suggesting that you immediately start dismantling your lens, but I seem remember having to do that once a long time ago with an M42 screw lens on a Russian camera, NOT a Pentax. That was probably a T-mount lens. They had a threaded adapter that was similar in size, but a slightly different thread pitch. |
#5
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"Siddhartha Jain" wrote in
oups.com: But somehow the horrible unsharpness at f/1.4 and the little difference in results between the kit lens and the Pentax 50mm left me thinking if I've been doing something wrong in the testing. The reason to buy the f/1.4 lens is to obtain f/1.4, not to obtain sharpness at f/1.4. Your results sound pretty much like what I would expect. Bob -- Delete the inverse SPAM to reply |
#6
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"Siddhartha Jain" wrote in message oups.com... Suggestions/pointers appreciated. 1: There is always the possibility that the adapter that you bought may be throwing things off. If you could get your hands on an Asahi Pentax screw mount camera, and conduct the tests using that, you might obtain improved results, in which case I would recommend that you obtain a genuine Asahi adapter, rather than an aftermarket one. 2: Your lens might be defective. Takumar lenses are well known for their sharpness, contrast and build quality. See: http://www.luminous-landscape.com/co...02-11-24.shtml 3: SMC Takumar lenses were tested by Popular Photography Magazine, and the Takumars tested sharper than the Leica lenses. Your test results are clearly out of line with the conventional wisdom regarding Takumar lenses. See: http://medfmt.8k.com/mf/rangefinder.html#keppler I really question the wisdom of testing a screwmount lens on a camera that uses another lens mount. If anything, your tests just might reveal that the use of aftermarket adapters may adversely affect lens sharpness. |
#7
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In article .com,
Siddhartha Jain wrote: But somehow the horrible unsharpness at f/1.4 and the little difference in results between the kit lens and the Pentax 50mm left me thinking if I've been doing something wrong in the testing. If a 50mm Takumar is taking "horribly unsharp" pictures, it's either broken or you're doing something wrong. Note that it can be very difficult to manually focus most autofocus bodies. On the other hand, you also say the Takumar is giving results similar to the kit lens - which should be at least decent. Just how bad ARE your results? Other than that the Pentax's focussing ring is damn smooth. Once I went back to the kit lens I was *shocked* by the jerky and wobbly focus ring. Completely normal, if unnerving. AF lenses are built to be focused with a minumum of movement and force, because of the tiny motors that usually do the focusing. Inside you'll find wide pitched, plastic rings with a minimum of lubricant. MF lenses can be MUCH more precisely made, with a fine metal helicoid and thick grease. |
#8
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Scott Schuckert wrote:
Just how bad ARE your results? http://www.geocities.com/losttoy2000...ax-resize.html http://www.geocities.com/losttoy2000...ntax-crop.html Unfortunately, I seem to have hit the data transfer limit on geocities Well, the horrible results are at f/1.4 only and not at other apertures, so could something still be wrong with the lens? Funnily, in the f/1.4 image, the part around the centre is a bit more sharper than the centre itself!! I am more inclined to think that I goofed up somewhere. - Siddhartha |
#9
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Siddhartha Jain wrote:
Unfortunately, I seem to have hit the data transfer limit on geocities Fixed. Now at fortunecity as well. http://members.fortunecity.com/lostt...ax-resize.html http://members.fortunecity.com/losttoy/pentax-crop.html |
#10
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Siddhartha Jain wrote:
Unfortunately, I seem to have hit the data transfer limit on geocities Fixed. Now at fortunecity as well. http://members.fortunecity.com/lostt...ax-resize.html http://members.fortunecity.com/losttoy/pentax-crop.html |
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