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12-15-2012, 06:12 AM   #1
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Extension tubes. Advice please?

Hi folks,

I have just bought a set of old extension tubes from Ebay, they don't have a manufacturer name on them but they do have an aperture lever. The lever on each moves freely on each one but I noticed that when I use an old manual lens on my camera and press the green button to meter there is a noticeable 'schnick' noise which I have always assumed is the camera operating the aperture lever. But when I put on the extension tubes and press the green button it no longer makes that noise, it still meters, presumably because the aperture is set manually on the lens anyway.

I suppose my question really is 'is this normal' or does the lack of noise suggest that the aperture lever on the tube is jamming the lever in the camera? I don't want to be using something that might damage my camera.

Also, I noticed that my DA* lens has an additional ramp shaped flange right next to the aperture lever that the old manual lens doesn't have, I strongly suspect this would block the aperture lever on the tube and potentially damage the lens - does anyone know why that additional flange is there?

Thanks in advance for any thoughts.

Cheers!

12-15-2012, 07:05 AM   #2
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I think an easy check would be to watch from the front. The aperture is wide open when mounted, the aperture stops down when green button is pushed.... Of course taking a few photos will help too. I can't see how it could hurt the camera - the lever does not move when lens apertures are set to their maximum in normal operation.
12-15-2012, 08:06 AM   #3
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I will recommend that you be careful which lenses you use with them, there are some optical designs that simply aren't well suited to having much more than 45.46mm of space behind their rear element, and it can cause some pretty odd behaviour from otherwise perfectly satisfactory lenses. I had one such issue arise from using my Sigma 180mm f/3.5 Macro lens (a non DG version, mind you) that developed a flare issue that only reared its ugly head at 1:1 focus with 25mm extension tube. It simply revealed a issue with internal reflection within the lens - the extension tube simply made it stand out more.

- this is the flare problem I encountered with my Sigma 180mm f/3.5 APO EX [IF] these spots would appear right in the middle of the frame.

So all I can say is be mindful of the lenses you use with them. Personally I use exclusively manual lenses on extension tubes, I never use my DA or DA* lenses on them - the reason for that is there is a big difference in way the aperture mechanism works between the older K~FA series lenses and the newer D-FA~DA* lenses that do not have aperture rings. I assure you there isn't likely to be any mechanical problems - it is simply the fact that DA and DA* lenses the camera controls the aperture electronically, with manual lenses you have all the control over the aperture used. The best way around this problem is to avoid it altogether. Also using extension tubes can cause the viewfinder to become darker and darker as you add more tubes, having a fast lens certainly comes in handy here - and having a fast lens helps with nailing the focus. Speaking of focusing I have been rather lucky with my extension tubes they are able to be used with all pentax K AF mount lenses with full auto-focus, and full automatic metering however, I never make use of this faculty, because at 1:1 and beyond even manually focusing can become a real challenge - and even the most advanced AF camera I own ( Nikon D4) cannot focus consistently at 1:1 with my Nikkor 105mm f/2.8G VR ED at f/2.8.

Last edited by Digitalis; 12-15-2012 at 07:28 PM.
12-15-2012, 08:25 AM   #4
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That's really really helpful - thanks a lot, guys!

12-15-2012, 10:53 AM   #5
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QuoteOriginally posted by Digitalis Quote
Personally I use exclusively manual lenses on extension tubes,
Me too, though I have used DA 21 Ltd in the past with no difficulties - just remember you are at minimum aperture when the camera stops down. From my Single In January 2012 so many months ago:



QuoteOriginally posted by Digitalis Quote
Also using extension tubes can cause the viewfinder to become darker and darker as you add more tubes, having a fast lens certainly comes in handy here - and having a fast lens helps with nailing the focus.
Adding extension effectively changes the FL of the lens you are using - that being said, the aperture value you register on the aperture ring can be up to 2 or 3 stops larger depending on the FL prime you are using, and the amount of extension. In my opinion, using a tripod is key to sharp shooting.

There are lots of "pro" level macro shooters here who have lots to share - I enjoy using extension tubes, but I have much to learn.


12-15-2012, 01:18 PM   #6
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Awesome snail!

(now that's not a phrase you hear everyday...)
12-15-2012, 01:28 PM   #7
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The preview (stop down) lever will not operate the lens if the tube doesn't make good electrical contact with the contacts in the camera lens mount; and in fact may not stop down when taking a picture - assuming it's a later Pentax dSLR. The camera uses the contacts just to sense if a lens is in place. You may need to "sand" the tube flange in the area of the contacts to get all to work.
Without that, it may take all pictures with the lens wide open (unless it is a Takumar with the A-M lever) which will give little depth of field.
12-15-2012, 07:30 PM   #8
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As you get further into exploring macro subjects you may also wish to include some flash equipment - which is another subject in itself, a challenging but extremely rewarding skill to learn how to work with light on small scale.




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