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09-22-2013, 03:18 AM   #1
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Stop Down Metering in K30 (with Extension Tube & Lens Reversed)

Hello guys, ive been reading about stop down metering, and up until now, i really have no clear understanding about it. From what i understand so far:

When Manual Lens Mounted Normally: (Im using Pentax SMC M 50mm 1.4)
On Manual Mode:
1. Tweak some settings on the camera to enable use of old manual lens to new DSLR body. Green Button, Enable aperture ring etc.
2. Set the desired aperture manually. (Aperture reading will be F00 since its M lens)
3. Focus on your desired subject.
4. Press Green Button to have the camera set the best shutter speed for that shot. (Light meter doesnt work)
5. Take your picture

So far, it works well. But can someone confirm if im on the right direction?

Also, can some PLEASE provide a simple and clear instruction on how to do stop down metering with the lens on an extension tube or with a lens reversed?
I tried using Vivitar Automatic Extension Tube i bought on ebay, new in box but very cheap. I mounted normally my M-50mm lens on the tubes and for some reason i cannot do the procedure above. I also tried have the lens mounted on reversed without the tubes, i cant do stop down metering. Its like trial and error.

i have read o the internet, someone said he set the aperture ring wide open, take a focus and meter, then set again the aperture as desired, then take the shot. Im confused how he did it on his Pentax camera.

Is it possible to Meter with extension tube on or with a reversed lens?
Or can someone give tips on how o do budget macro using the materials mentioned how to have a correct exposure, etc/
Sorry for the very long post. Thank you guys. I hope youll help me out...

09-22-2013, 05:09 AM   #2
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Are your extension tubes of the "auto" variety? If so no, change to stop down process. I can't comment about non auto tubes. I've never used a reversing ring.

As for "metering" - why not just chimp and adjust using the histogram? One great benefit of digital is the economy on a per shot basis.
09-22-2013, 08:01 AM   #3
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i used "auto extension tube" from vivitar but has no electrical contacts
09-22-2013, 09:30 AM   #4
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Green button metering doesnt need any electrical contacts, I use Asahi Pentax auto extension tubes... the Auto refers to the aperture linkage (wrt say M42 manual apertures). The stop down metering operation is exactly the same as when a K or M lens is mounted directly.

Just noticed you are using Vivitar tubes. If they are painted you will need to sand the paint off so that the body knows there is a "k or m" lens mounted.

09-22-2013, 11:46 AM   #5
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Right if the the tubes do not have bare metal on the mount you will have to remove some of the coating in order for the K-30 to stop-down. You can test this by putting a bit of thin metal foil over the contact area as you mount the tubes. Note also that the instructions for the tube say to mount the tubes on the camera body before mounting the lens in order for everything to line up properly. You can take them apart in any order. I think you only need to remove the coating over the "seventh" (data) pin.

Using a reversed lens is similar to using a screwmount lens. Focus wide open, compose, stop down manually to the desired f-stop, push the green button, tweak shutter speed - take your picture. If you are using an "A" lens reversed you have to take it out of "A" mode.
09-23-2013, 11:43 PM   #6
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With m42 lenses and probabily with reverse adapters you can use AV mode, no need to use green button,
naturally the aperture must be set on the lens, but there is the possibility that you cannot change
the aperture if the lens it's not mounted correctly ie the lens stay always open ore closed
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