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03-23-2013, 09:56 AM   #1
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I cant seem to get the aperture working as it should

Hi all, i recently purchased a used Pentax k-30 along with a 18-55mm AF zoom lens and they i also bought an old used 50mm manual focus lens a little later. Ive spent all of today playing with the 50mm lens but it seems that turning the aperture ring seems to do very little with regard the outcome of my photos, be it fully open or fully shut they look the same. (same problem with the the 18-55mm zoom lens)

i could upload some photos to show you if need be but basically the focal length dosnt seem to change at all, there must be some setting someplace that i need to change that i have overlooked?

I take 2 photos, all settings exactly the same except turning the aperture ring fully each way (i know it physically is turning, i took it off and looked at it) and the 2 photos look nearly exactly the same except maybe one is a tiny bit brighter. i then flicked it into video mode and in the preview screen before starting recording it looks like the same problem but as soon as i start recording the aperture ring works as you would expect.. opening the lens makes things alot brighter and less grainy and decreases focal depth very noticably so why does it not work for me when trying to take stills? ive tried both auto mode and TAV (aperture priority mode)

03-23-2013, 10:07 AM   #2
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What mode are you shooting in?
Have you enabled using aperture ring in the menu?
03-23-2013, 10:10 AM   #3
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tried shooting in all modes i believe, yes i had to enable that in the menu cause before i did that the camera wouldnt fire at all. I got the camera and lenses 2nd hand and it didnt come with a manual and this is my first jump to DSLR from a compact so its all a bit new to me.
03-23-2013, 10:19 AM   #4
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With the 50mm manual lens wouldn't you want to set the camera to aperture priority?

On my K10D when I use manual lenses, there is a setting to tell the camera what the focal length is. If I don't set it prior to taking pictures then the camera doesn't know the focal length.

And when shooting with the manual lenses, I shoot in aperture priority, set the aperture, and the camera chooses the shutter speed for the correct exposure.

03-23-2013, 10:23 AM   #5
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QuoteOriginally posted by Racer X 69 Quote
With the 50mm manual lens wouldn't you want to set the camera to aperture priority?

On my K10D when I use manual lenses, there is a setting to tell the camera what the focal length is. If I don't set it prior to taking pictures then the camera doesn't know the focal length.

And when shooting with the manual lenses, I shoot in aperture priority, set the aperture, and the camera chooses the shutter speed for the correct exposure.
Only with an A series lens. All Pentax DSLRs have a crippled K mount so you need to use stop down metering (Green Button) in M mode with all manual lenses. In Av the lens will always be wide open.

https://www.pentaxforums.com/forums/pentax-beginners-corner-q/110658-using-ma...x-dslrs-f.html
03-23-2013, 10:23 AM   #6
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there was a setting i changed to '50mm' because the camera couldnt auto detect what the lens was. the setting was called "input focal length" did i set it right, i thought it must be 50mm cause its a 50mm lens.
03-23-2013, 10:25 AM   #7
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I'm a bit confused here. You say "50mm lens but it seems that turning the aperture ring seems to do very little with regard the outcome of my photos, be it fully open or fully shut they look the same. " then you say "(same problem with the the 18-55mm zoom lens)"
If this is the Pentax 18-55 you can't possibly be having the same problem with the aperture ring as you have with the 50 as the 18-55 doesn't have an aperture ring.
If by Auto you mean aperture priority, they should look the same. You are choosing the aperture and the camera is choosing the appropriate shutter speed.
TAV is not aperture priority. In TAV you select the aperture and shutter speed, the camera selects the ISO to give you proper exposure; so the pictures should look the same in that mode as well.
03-23-2013, 10:28 AM   #8
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the prime lens is a Pentax-M SMC 50mm f1.7 if that helps.

Parallax: Yes, the 18-55mm AF lens dosnt have an aperture ring, with it i need to put the camera into eg. TAV mode i think, and then i can use one of the scroll wheels on the camera to adjust the aperture, but regardless of what setting i put it at my depth of field dosnt seem to change at all though i can see the aperture changing on the screen on the back of the camera.

03-23-2013, 10:31 AM   #9
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QuoteOriginally posted by Parallax Quote
TAV is not aperture priority. In TAV you select the aperture and shutter speed, the camera selects the ISO to give you proper exposure; so the pictures should look the same in that mode as well.
shouldnt the blurriness of things in the background change as you change the aperture in this mode?
03-23-2013, 10:33 AM   #10
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QuoteOriginally posted by MADDSNIPER Quote
the prime lens is a Pentax-M SMC 50mm f1.7 if that helps..
Follow the instructions in the link I posted. An M series lens has to be used with the Green Button in M mode. Also make sure Auto-ISO is turned off or M mode won't work on the K-30...
03-23-2013, 10:42 AM   #11
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QuoteOriginally posted by boriscleto Quote
Only with an A series lens. All Pentax DSLRs have a crippled K mount so you need to use stop down metering (Green Button) in M mode with all manual lenses. In Av the lens will always be wide open.

https://www.pentaxforums.com/forums/pentax-beginners-corner-q/110658-using-ma...x-dslrs-f.html
Thank you Boris. I keep learning more and more from helpful PentaxForums members like you!
03-23-2013, 10:42 AM   #12
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ok i put the camera in M mode, (the writing comes up on the screen telling me its av mode, makes it seem that av mode, tav mode and m mode are all the same with this lens) the green button dosnt really seem to be doing anything though the camera knows im pressing it, i took 2 photos one with aperture 1.7 and one with aperture 22. they both look exactly the same. i will resize them both and upload now to show you guys.
03-23-2013, 10:44 AM   #13
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QuoteOriginally posted by MADDSNIPER Quote
shouldnt the blurriness of things in the background change as you change the aperture in this mode?
Only on the actual pics, not as you change the settings as the lens is wide open until you actually shoot. Can you upload pics to flickr or something?
03-23-2013, 10:45 AM   #14
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QuoteOriginally posted by MADDSNIPER Quote
the prime lens is a Pentax-M SMC 50mm f1.7 if that helps.

Parallax: Yes, the 18-55mm AF lens dosnt have an aperture ring, with it i need to put the camera into eg. TAV mode i think, and then i can use one of the scroll wheels on the camera to adjust the aperture, but regardless of what setting i put it at my depth of field dosnt seem to change at all though i can see the aperture changing on the screen on the back of the camera.
You can also do that in Manual, and Aperture Priority.

QuoteOriginally posted by MADDSNIPER Quote
shouldnt the blurriness of things in the background change as you change the aperture in this mode?
In your original question you said that the pictures looked the same. I took that to mean that you were wondering why they were all exposed the same. Now I see we're discussing DOF.
As to whether the blurriness of the background should change or not; it depends on the distance to your subject, the focal length of the lens, and the distance between your subject and the background. The simple answer is that the farther you are from your subject, the less difference you will see. If you are far enough away that your subject and background are within the hyperfocal distance for the aperture you are using then they both will be in focus. In the case of the 18-55, you aren't going to see much difference no matter what. At the wide end, you have a very large DOF due to the relatively small (3.5) aperture and wide angle of the lens. At 55mm the even smaller f5.6 aperture is going to have the same effect.
03-23-2013, 10:46 AM   #15
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QuoteOriginally posted by MADDSNIPER Quote
ok i put the camera in M mode, (the writing comes up on the screen telling me its av mode, makes it seem that av mode, tav mode and m mode are all the same with this lens) the green button dosnt really seem to be doing anything though the camera knows im pressing it, i took 2 photos one with aperture 1.7 and one with aperture 22. they both look exactly the same. i will resize them both and upload now to show you guys.
Turn off Auto ISO. The K-30 has what IMO is a bug. If Auto ISO is turned on M mode doesn't work...this is because it inherited most of its firmware from the K-01 where Auto ISO in M mode is a stealth TAv mode. Older Pentax DSLRs automatically turn off Auto ISO when the camera is set to M.

You also have to set the Green Button to function as Green Button...

Last edited by boriscleto; 03-23-2013 at 10:54 AM.
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