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06-11-2016, 06:27 PM   #1
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What are these red and purple lines?

G'day everyone, how are you? I have a SMC Pentax K 300mm F4 lens, and the aperture doesn't stop down when it's on the camera (pentax k-x dslr). When I touch the aperture lever off the camera, however, it stops down. Does anyone know what the problem is? Is it repairable?

My photos taken with this camera also have red and purple lines running around the subjects, as seen in the crops below- does anyone know what they are?

Thank you!

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06-11-2016, 06:33 PM - 1 Like   #2
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QuoteOriginally posted by bessa-66 Quote
G'day everyone, how are you? I have a SMC Pentax K 300mm F4 lens, and the aperture doesn't stop down when it's on the camera (pentax k-x dslr). When I touch the aperture lever off the camera, however, it stops down. Does anyone know what the problem is? Is it repairable?

My photos taken with this camera also have red and purple lines running around the subjects, as seen in the crops below- does anyone know what they are?

Thank you!
This behavior is normal. The lens should stop down when you go to take a photo, otherwise it will stay open.

Make sure you follow these instructions to meter correctly:
https://www.pentaxforums.com/forums/54-pentax-lens-articles/110657-how-use-me...k-x-k-7-a.html

What you're seeing in the photo are chromatic aberrations, which are common on older telephoto lenses that do not employ corrective elements. Stop down to reduce their severity. Also, while I won't go in detail, things that aren't in focus typically exhibit more aberrations than things that are. That's why the boat has all those halos, while the houses just have a small amount of fringing.

Adam
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Last edited by photolady95; 06-11-2016 at 06:45 PM.
06-11-2016, 06:37 PM   #3
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https://en.wikipedia.org/wiki/Chromatic_aberration

you can correct them in post processing too
06-11-2016, 06:43 PM   #4
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Thanks for the reply guys! Adam, the lens doesn't stop down when the photo is taken- it stays wide open for some reason. I've put the camera into bulb mode and set the ring to f22 and didn't see it close down like on my other lenses. Any ideas?

06-11-2016, 07:02 PM   #5
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QuoteOriginally posted by bessa-66 Quote
Thanks for the reply guys! Adam, the lens doesn't stop down when the photo is taken- it stays wide open for some reason. I've put the camera into bulb mode and set the ring to f22 and didn't see it close down like on my other lenses. Any ideas?
Did you set your camera's aperture ring custom function to allowed? See the instructions at the link Adam provided.
06-11-2016, 07:33 PM   #6
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QuoteOriginally posted by Quartermaster James Quote
Did you set your camera's aperture ring custom function to allowed? See the instructions at the link Adam provided.
Sure did!
06-11-2016, 07:49 PM   #7
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QuoteOriginally posted by bessa-66 Quote
Sure did!
And you are metering with the green button?
06-11-2016, 09:06 PM   #8
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QuoteOriginally posted by bessa-66 Quote
Sure did!
If so, the lens should stop down to the setting on the aperture ring for exposure. If it does not, you should confirm that the body is able to consistently stop down other lenses that you might have.


Steve

06-11-2016, 09:31 PM   #9
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Hi Steve, I meter using the green button, and the shutter speed changes accordingly. But when I twist the aperture ring to another value, the shutter speed doesn't change (if I'm pointing at the same subject). There is no clicking noise as with my other lenses. Checking now just to be sure
06-11-2016, 09:51 PM   #10
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QuoteOriginally posted by bessa-66 Quote
Hi Steve, I meter using the green button, and the shutter speed changes accordingly. But when I twist the aperture ring to another value, the shutter speed doesn't change (if I'm pointing at the same subject). There is no clicking noise as with my other lenses. Checking now just to be sure
If I understand what you are saying correctly, everything is operating as it should. The shutter speed isn't going to change again until you meter with the green button again. If you meter, then change the aperture, then your exposure is going to be off.
06-11-2016, 10:11 PM   #11
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QuoteOriginally posted by bessa-66 Quote
Hi Steve, I meter using the green button, and the shutter speed changes accordingly. But when I twist the aperture ring to another value, the shutter speed doesn't change (if I'm pointing at the same subject). There is no clicking noise as with my other lenses. Checking now just to be sure
QuoteOriginally posted by Quartermaster James Quote
If I understand what you are saying correctly, everything is operating as it should. The shutter speed isn't going to change again until you meter with the green button again. If you meter, then change the aperture, then your exposure is going to be off.
What he said. You are in manual mode. The green button stops the lens down for a moment and changes the shutter speed to match, but when it opens back up you are fully manual again.


Steve
06-11-2016, 11:58 PM   #12
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I think it might be the aperture linkage for this 300mms lens... Maybe it's out of alignment or something- in manual mode, I tested with another lens and it did stop the aperture down. The 300mm is 45 years old after all!
06-12-2016, 12:13 AM   #13
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Is the mount black or powdered or something? If the contacts are not making contact the body might think you are having an 'A' on the lens since the 'A'-contact (which should be making contact) is not contacting.
Of course I guess you are using the body in using the lens in the setting that it would use 'non-A' lenses? Although I mainly shoot with manual lenses withouth 'A', I sometimes forget the setting... and then it stays open during exposure (and if the body experiences an 'A'-lens it uses the calculated value of the body/the movement that would go with the aperture-setting on the body).
You can try in lifeview what the lens does: if it closes down, the linkage is working as it should ( I don't remember if the K-x does has lifeview though)
06-12-2016, 12:28 AM   #14
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QuoteOriginally posted by bessa-66 Quote
is 45 years old after all!
What's your point here, I'm older than that and I still work... well most of the time.
06-12-2016, 01:30 AM   #15
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Hi guys, just tried to stop down my other manual lenses, and I can see the diaphragm stop down when I press the button. Not so with the 300... it does stick when I press it down off the camera- is there any chance that this can be fixed with a little oil or something?

---------- Post added 06-12-16 at 01:30 AM ----------

QuoteOriginally posted by Kerrowdown Quote
What's your point here, I'm older than that and I still work... well most of the time.
Aaah, but you're not a glass tube! :P

---------- Post added 06-12-16 at 01:32 AM ----------

QuoteOriginally posted by elvinhaak Quote
Is the mount black or powdered or something? If the contacts are not making contact the body might think you are having an 'A' on the lens since the 'A'-contact (which should be making contact) is not contacting.
Of course I guess you are using the body in using the lens in the setting that it would use 'non-A' lenses? Although I mainly shoot with manual lenses withouth 'A', I sometimes forget the setting... and then it stays open during exposure (and if the body experiences an 'A'-lens it uses the calculated value of the body/the movement that would go with the aperture-setting on the body).
You can try in lifeview what the lens does: if it closes down, the linkage is working as it should ( I don't remember if the K-x does has lifeview though)
Hi Elvinhaak, this lens has no A setting on the ring at all
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