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01-01-2014, 03:37 PM   #1
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Strange defect with smc 50mm f2

Hi there. I am a entusiast pentax forums, I read a lot of this forum, and I want to share with you a defect that I have with my old SMC Pentax-M 50mm F2 attached to my pentax k-5. I donīt know with is that. Can you tell me? There was a hard light at the right, but the defect is really heavy. Do you know why is that? The iso was a 1600, the exposure 1/100 and I think It was f8 or similar.



If you could help me, I would aprecciate.

The other thing that happens to me with this lens, is that I put it in f22, and the depth of field is like it was in f6 or 8, or similar, is low. Why can be that?

Thanks in advice. and sorry for my english.
Greetings.
Florencia.

01-01-2014, 04:08 PM   #2
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That kind of light is hard to shoot in, and that's how it ends up looking, especially at high isos. It's not the lens's fault.

As for the depth of field, take the lens off the camera and verify that the aperture diaphragm is working properly. You can also use the dof preview feature to check it.

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01-01-2014, 04:19 PM   #3
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LED lighting?
01-01-2014, 04:27 PM   #4
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Why f/8, 1/100 and ISO 1600?

01-01-2014, 06:07 PM   #5
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Thanks for the replies.
I'm glad that is not a lens's fault.

I'm an amateur photographer, and in low light is dificult for me to take good photos. I don't know if the light was of led but it was very very hard light.
I was using 1600 iso because of the low light, 1/100 to keep the subjects still and focus, and the f8 was because I didn't want to have a very low DOF. Sure is not the best configuration, but I am learning.

About the aperture diaphragm of the lens, I check it outside the camera and it works of. I will do the test with the dof preview feature to see what happen.

Thanks.
01-01-2014, 07:13 PM   #6
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Yep...LED stage lighting.


Steve
01-01-2014, 10:09 PM   #7
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Tinted LED lighting can be extremely tricky, and sometimes the only way to get a good shot is to underexpose quite a bit. Higher ISO also makes it harder to fit the light into the the histogram as the dynamic range gets smaller. Also if you shot JPEG it makes it harder to save than if it was raw.

Try an image processor like Photoshop, Lightroom or Aperture and experiment with the purple, magenta and blue color channels to see if it's recoverable. If not change it to black and white and try to make it usable that way.

Good luck and you are not the first nor the last to face this issue with stage lighting so see it as a learning experience.

Here's a couple of LED stagelighting cases I managed to save, but non were as burned your pic.






01-02-2014, 08:18 AM   #8
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Perfect. Thank you very much for the help.
Next time I will try to underexpose a little and put a lower iso.
Thanks to everybody!

01-12-2014, 06:37 PM   #9
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Sorry to bother again, about the aperture diaphragm of the lens, I did the test outside the camera, and the diaphragm works all right, but in the camera, is not working well. I send you 2 photos, one with f2.0 and the other with f22. The thing is that the DOF is working in f22 like it were in f2.0 but I know the diaphragm is close because I have to put a low time of exposure to get the same light. Something is not right, any thoughts? The first is with f2.0 and the second with f22.





Thanks in advice!
01-15-2014, 07:23 AM   #10
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You have to be in manual mode. So, are you in manual mode?
01-15-2014, 10:21 AM   #11
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QuoteOriginally posted by flosampodg Quote
Something is not right, any thoughts?
Problem is you expect to see something that is not the result of your setup.

f/2 -> thin DOF
f/22 -> wide DOF

still keep in mind that:

focus close -> thin DOF
focus far -> wide DOF

you're just too close at 0,5 meters to see to infinity, since the background is far away in relation to you and your focus point - so the DOF is thin and that's that.

pick the tripod+camera up, move it 10 steps back, focus carefully again to the bottle, and see if f/22 does something then.
01-16-2014, 02:25 AM   #12
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QuoteOriginally posted by flosampodg Quote
The other thing that happens to me with this lens, is that I put it in f22, and the depth of field is like it was in f6 or 8, or similar, is low. Why can be that?
This is likely to be softness caused by the diffraction limit, not DOF. That is a fundamental law of physics which shows up on high resolution sensors.
01-20-2014, 12:57 PM   #13
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Thanks for the help! I was using the old lens in others modes but not in manual. Now it works like a charm
Thanks!
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