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02-11-2012, 08:38 AM   #1
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Sharpness and metering problems with Bellows on the K-5

Howdy,

Just scored the following set on fleabay in good shape and for a price too low to dare mention here :

Carena Double Glide Bellows, SMC Pentax-M 1:4 100mm Macro, SMC Pentax-M 1:1.7 50mm


I've tried both lenses with the bellows, and the 100mm gives the most convenient focusing distance to work on the few bugs I've found.

However the bellows don't seem to have electrical contacts so Green button metering doesn't work when I use M mode, and I'm only metering properly through trial and error.

Moreover, my pictures seem somewhat soft even with a tripod and perfect focus using live view, and changing the aperture via the ring doesn't seem to make any difference, am I doing something wrong ?

02-11-2012, 09:24 AM   #2
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Please tell us what the camera body mount on the bellows is like, (black anodized or blank metal?). For light metering there might be an issue of electrical contact if you are using a newer Pentax body.

Anyway, if available light is very low, Green Button metering will not be too reliable. But surely, stopping down your lens in manual mode should produce a visible difference. Have you convinced yourself that the aperture coupler on the bellows work properly? You can test that by stopping down the lens completely, mount it on the bellows and see if the diaphragm opens up when you push the coupling lever on the bellows.

Last edited by Stone G.; 02-11-2012 at 09:30 AM.
02-11-2012, 09:25 AM   #3
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Hi

M won't work there is no mechanical connection to the lens, use Av with manual lenses. You don't need that Green button
nonsense in Av mode. If you want to change the exposure then use the AV+- adjustment.
02-11-2012, 10:03 AM   #4
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Thanks for the answers.

Looks like my lens was staying wide open all the time, hence my sharpness problem.

Bobpur, if I use Av mode and thus the aperture ring will I be able to focus wide open, or will the viewfinder darken ?

02-11-2012, 10:09 AM   #5
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I don't know that model bellows. Is it an "auto bellows" that holds the lens open until a dual cable release closes it? If it's a manual bellows the lens will stop down as you change the aperture setting, but an auto bellows does not. So if it's an auto unit your lens may be staying wide open.
An auto bellows normally uses a dual cable release that stops the lens down before the shutter fires. Of course, the K-5 doesn't use a cable release, but you still need one to close the lens on an auto bellows. (The Pentax Auto Bellows A allows you to press in on the button where the cable release attaches to stop down without a release.)
02-11-2012, 10:16 AM   #6
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QuoteOriginally posted by bobpur Quote
M won't work there is no mechanical connection to the lens, use Av with manual lenses. You don't need that Green button
nonsense in Av mode.
Av is frequently inaccurate by a stop or two when used with fully manual lenses. It does "work" in the sense that it will make the best guess it can, but manual mode and green button metering will be consistently more accurate, which would be why this button came about in the first place. The camera doesn't have to control the aperture to effectively meter in manual mode.

QuoteOriginally posted by Matchete Quote
However the bellows don't seem to have electrical contacts so Green button metering doesn't work when I use M mode
There doesn't need to be electrical or mechanical linkage to meter with the green button. You just need to stop down the lens manually, first. Shorting contacts is only relevant when you're using stop down metering with mechanical linkage, because it allows the camera to close the aperture to where you set on the aperture ring. It doesn't apply when using bellows, provided the bellows isn't keeping the lens wide open. It sounds like TomB_tx's idea may be the issue here.
02-11-2012, 10:43 AM   #7
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Here is a picture of the bellows. I'm pretty sure that they are manual.

Philoslothical green button metering doesn't work with the 100mm mounted on them, but works with the 100mm on its own.

And I don't see any noticeable difference when I stop the lens down manually.
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02-11-2012, 11:13 AM   #8
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I use a similar setup all the times. I mostly use a ring flash or multiple flashes to have better control of the light, but here are a couple ways to get a correct exposure with available light.
  1. Keep your lens wide open and focus (Live View will help a lot here)
  2. Set the camera in Av mode so you get continuous exposure readings. Essentially you are using the camera as an exposure meter.
  3. Note the measured shutter speed. This will be for the lens wide open. You can calculate the real speed when you close the lens to the desired f-stop. For example if you used your M 100 which is F4 and measure wide open 1/250, then if you stopped down to F8 the speed now should be 1/60.
  4. Switch the camera to M, set the calculated speed, set the lens aperture ring to F8 on the lens and take the picture.
If there is plenty of light and get speed readings in the hundreds, you can keep the camera at Av and manually close the lens (after focusing) to the F-stop you like. The camera will continue to measure the incoming light and since the lens is physically closed down, the exposure will be correct. If the light is not strong though, and you stop the lens at F16 or F22, it may be too dark for the camera to accurately measure the exposure so use the method above.

02-12-2012, 08:38 AM   #9
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I have the same Pentax bellows as described by TomB. I use mine mostly to scan negatives, but the results are the same if you use them for taking bug photos. First step, set the camera to M. Second, leave the lens wide open to focus using the viewfinder, not live view. Third, stop the lens down using the aperture ring and lock it down with the button on the bellows. Forth, block the viewfinder from extra light entering and use the green button to meter. Last, take the shot.

My shots come out very sharp and the exposure is correct. If I do need to compensate the exposure I use the -/+ compensation. I also have extension rings and use the same procedure. The best lens that I have for this is a 50mm Pentax macro f2.8. Most of my shots are in the f8 to f11 range. Hope this helps.
02-12-2012, 10:37 AM   #10
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QuoteOriginally posted by toooldtocare Quote
I have the same Pentax bellows as described by TomB. I use mine mostly to scan negatives, but the results are the same if you use them for taking bug photos. First step, set the camera to M. Second, leave the lens wide open to focus using the viewfinder, not live view. Third, stop the lens down using the aperture ring and lock it down with the button on the bellows. Forth, block the viewfinder from extra light entering and use the green button to meter. Last, take the shot.

My shots come out very sharp and the exposure is correct. If I do need to compensate the exposure I use the -/+ compensation. I also have extension rings and use the same procedure. The best lens that I have for this is a 50mm Pentax macro f2.8. Most of my shots are in the f8 to f11 range. Hope this helps.
Shooting negatives and photographing bugs are totally different processes. Negatives are practically flat and require very thin DOF to guaranty correct focus and sharpness even when using a relative wide f-stop (e.g. F5.6 or F8). Bugs being 3-Dimensional require much greater DOF and super critical focus. The viewfinder is fine for focusing on a flat surface but for a 3-D object there is no comparison using Live View and enlarging 6x the subject.

You can use the green button to measure (after you close the lens, in which case Av mode will do the same) only if you have enough light. The camera's light meter is sensitive to around 0EV (some models are -1EV and others +1EV). If the light is not strong (e.g. 5EV) and close the lens down 5 stops, you are already at the camera's low limit. Using bellows you loose another 1 or 2 stops depending on the extension making things even worse. That's why all metering in camera's is done with the lens wide open and then calculate the exposure at the f-stop selected. The green button is for convenience for manual lenses and works great for average situations, but it has its limitations.
02-12-2012, 11:57 AM   #11
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QuoteOriginally posted by demp10 Quote
Shooting negatives and photographing bugs are totally different processes. Negatives are practically flat and require very thin DOF to guaranty correct focus and sharpness even when using a relative wide f-stop (e.g. F5.6 or F8). Bugs being 3-Dimensional require much greater DOF and super critical focus. The viewfinder is fine for focusing on a flat surface but for a 3-D object there is no comparison using Live View and enlarging 6x the subject.

You can use the green button to measure (after you close the lens, in which case Av mode will do the same) only if you have enough light. The camera's light meter is sensitive to around 0EV (some models are -1EV and others +1EV). If the light is not strong (e.g. 5EV) and close the lens down 5 stops, you are already at the camera's low limit. Using bellows you loose another 1 or 2 stops depending on the extension making things even worse. That's why all metering in camera's is done with the lens wide open and then calculate the exposure at the f-stop selected. The green button is for convenience for manual lenses and works great for average situations, but it has its limitations.
I agree with most of your statement. However, shooting negatives is just hard as bugs, I also shoot closeups of flowers, but not bugs. Negatives gives a particular problem because if your DOF is off and you focus on the center, than the edges will be out of focus. This is why many people reverse the lens to get a flat field effect. I use a flat field lens so I do not have to reverse it, but I have in the past before I got the lens.

I use window light to illuminate my shots because I do not have to do much color correction, so there is also plenty of light to operate the light meter. I assume that when the OP shoots bugs he is outside, thus would have the same amount of light. Having shot weddings for 40 years (10 as a full time professional) using a Mamiya TLR with bellows, I fully understand the light fall off of when extending them. I had to calculate the effect when taking close ups of the hands etc because the Mamiya is a totally manual camera. But, using the K5 in M will give correct readings when stopped down because the camera sees the light hitting it, not calculating what the light would be if it were wide open. This is especially true using window light.

When I shoot some of my flowers I use tungsten light and a black background. I also shoot those at f8 to f11 to get the good DOP. I have had good luck using my bellows for that. What I was saying to the OP was to try M and stop the lens down and let the camera do the work.

Attached is one of those shots using tungsten light and the bellows.
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02-12-2012, 03:52 PM   #12
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Demp10 and Tooldtocare thanks a lot for the explanations, but despite making several attempts with each of the advised methods I don't see any improvements.

I'm almost certain that my bellows are forcing my lens to stay wide open.

I haven't tried using them in very good light though, whether it be with a ring flash or during a really sunny day, that could solve my "green button problem", but would that magically reanimate my bellows ?
02-12-2012, 04:34 PM   #13
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Look in the lens when you have set a f stop other than wide open. Is it stopped down? Unless you have a bellows like mine that does have a cable release, it should be noticable when not wide open. If it is not, than the bellows is preventing it from stopping down because there are no connections from the camera to the lens. I doubt that this the case though.
02-12-2012, 04:47 PM   #14
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QuoteOriginally posted by Matchete Quote
I'm almost certain that my bellows are forcing my lens to stay wide open.
Machete, in your second pic above, is that a switch in the lower left of the lens mount? If you depress that lever or switch, does the lens stop down? There must be some kind of manual trigger on the bellows for this, if there's no cable release jack.
02-12-2012, 05:00 PM   #15
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Looking at the image of the bellows rear mount, the one that couples with the camera, I can see a protruding level like an aperture control lever. Is this somehow connected to the from on the bellows? Do you see something in the front mount that will keep the lens open?

When you mount the lens and the bellows and then start closing the lens toward F32, you must see the viewfinder getting significantly darker. If not then the front of the bellows has something that keeps the lens wide open. You should be able to see the aperture blades closing very easily.Try to half mount the lens and see if the aperture closes.

Can you post images of the front and back of the bellows?
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