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01-02-2014, 12:15 PM   #1
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Pentax SMC-M 50mm f1.4

Hi,

I recently bought a pentax smc-m 50mm f1.4 lens and i am using it on my canon 550d with the help of a adapter, i have seen a lot of good reviews about this lens but in my case its not working that much good. Most of the pics are not sharp at all, i tired everything (shooting still objects and using tripod) even then its not up to mark. I am confused whats wrong here?

Is the problem with the lens or camera ?

Thanks

01-02-2014, 12:54 PM   #2
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QuoteOriginally posted by yepee9 Quote
Hi,

I recently bought a pentax smc-m 50mm f1.4 lens and i am using it on my canon 550d with the help of a adapter, i have seen a lot of good reviews about this lens but in my case its not working that much good. Most of the pics are not sharp at all, i tired everything (shooting still objects and using tripod) even then its not up to mark. I am confused whats wrong here?

Is the problem with the lens or camera ?

Thanks
Can you post some samples? If you're shooting wide-open the whole time, the image quality will of course not be as great as when stopped down, but it's hard to say without seeing some photos. This lenses is otherwise a very solid performer! Also, make sure the lens is mounted properly since it's not a native Canon lens.

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01-02-2014, 12:57 PM   #3
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Using any lens on a camera it wasn't originally intended to work with is always a chancy thing. In your case the focus could be off just a bit and there are several variables that could cause this to happen. For starters, the focus screen on the Canons were not intended for manual focus so you may not be able to easily tell when you are in or out of focus. Next, if the adaptor is not correctly built to place the lens the correct distance from the sensor it will not focus correctly. Finally, the lens itself could be having problems.

The first thing I would try is to lay a meter stick or yardstick on a table, focus on the middle number and take a picture. Print the picture and then look at it to find out which numbers are actually in focus to see if you are front focusing or back focusing.
01-02-2014, 01:06 PM   #4
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The depth of field is small at f1.4 and close up. Your viewfinder won't show it accurately either - it will show more depth of field than the image will have. So the first check is to take a shot kind of like this, maybe more carefully. The subject should have some detail in the frame from front to back. Shoot it at an angle so the distance varies within the shot. Shoot wide open. A tripod will make this shot more consistent and allow you to test further. This shot is at 50mm, f1.7 because that's what was on the camera, just about minimum focus distance. The shot only shows something is in focus, a good starting point.



Then you could take the same shot at different apertures. If your first shot was well-exposed at say f1.4, ISO 200 and 1/60, then keep ISO fixed, stop down to f2.8 and drop the shutter speed to 1/15. You should get the same image brightness (roughly) and more depth of field. The f2.8 shot should be sharper in the center and have more contrast too. You can keep doing this at other apertures and compare the resulting shots.

Another test is to shoot a detailed flat subject maybe ten feet away, with the camera's sensor parallel to the subject plane. The left side should be as sharp as the right. The M50/1.4 has a slightly curved focus plane which is more obvious at close distances with this test, but it's not supposed to be lopsided.

A test shot with bright out of focus highlights might be useful. Christmas lights are good. You can shoot wide open and the highlights should be round. Stopped down should show the shape of the aperture blades.

01-03-2014, 08:03 AM   #5
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does the 50/1.4 experience focus shift? Regardless fast 50s are difficult to manually focus. Have you shot using live view?
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