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07-27-2012, 03:06 PM   #1
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645 or 67 lens to be used w/ tilt shift adapter?

Hi,

I am trying to figure out the best option for getting a T/S lens on my K20 to do mostly product shots. I have read a lot but I still need some advice on how to proceed. I have been looking into getting a Mirex T/S adapter for Pentax 645 lenses. I am confused as to what are the differences between the 645 & 67 lenses? I really know nothing about the 2 formats. Do they have different mounts? Are the lens' optical circles different sizes?

I know getting the adapter & a 45 or 80mm lens would be more expensive than getting one of the Arax lenses I see on ebay. Are the Arax lenses medium format lenses as well as the 645 lenses? I have read a couple of folks arguing whether or not you get get a pronounced tilt / shift effect on the smaller sensor camera like the K20. As I said I will be doing mostly product shots , so more tilting & swinging than shifting.

I have been in touch with the Mirex folks about their adapters and am just a little apprehensive about going the route of the adapter & 645 lens because of the expense and me not knowing how well they would work.

Does anyone have experience with both setups (the Arax & adapter plus lens)? The adapter setup seems a little more appealing for being able to use arguably better glass, and the ability have more than one focal length as I get more lenses.

Any thought or advice would be greatly appreciated.

Thanks!

George

07-27-2012, 03:33 PM   #2
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I do not know anything about the T/S adapter you mention but the conversion of a 6x7 or 645 lens to K mount is fairly straight forward. Both 6x7 and 645 mounts are, of course, larger than the k mount and there will be no connection, mechanical or electrical to the lens but it's very simple to do stop-down metering in manual mode on the K20. I'm not versed well enough to say anything about the optical circles but I can say that my 6x7 & 645 lenses with adapters to K-mount work just like any manual lens on my K20 and K5. Hopefully someone else has more to add on this.

Oh, you can also get an adapter to convert 6x7 lenses to 645 mount but taking that then to a k-mount might be a bit weird.
07-27-2012, 06:03 PM   #3
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QuoteOriginally posted by gsrokmix Quote
Hi,

I am trying to figure out the best option for getting a T/S lens on my K20 to do mostly product shots. I have read a lot but I still need some advice on how to proceed. I have been looking into getting a Mirex T/S adapter for Pentax 645 lenses. I am confused as to what are the differences between the 645 & 67 lenses? I really know nothing about the 2 formats. Do they have different mounts? Are the lens' optical circles different sizes?

I know getting the adapter & a 45 or 80mm lens would be more expensive than getting one of the Arax lenses I see on ebay. Are the Arax lenses medium format lenses as well as the 645 lenses? I have read a couple of folks arguing whether or not you get get a pronounced tilt / shift effect on the smaller sensor camera like the K20. As I said I will be doing mostly product shots , so more tilting & swinging than shifting.

I have been in touch with the Mirex folks about their adapters and am just a little apprehensive about going the route of the adapter & 645 lens because of the expense and me not knowing how well they would work.

Does anyone have experience with both setups (the Arax & adapter plus lens)? The adapter setup seems a little more appealing for being able to use arguably better glass, and the ability have more than one focal length as I get more lenses.

Any thought or advice would be greatly appreciated.

Thanks!

George
Evening George,

I had a K20 that I used the Pentax K 28 Shift lens on (I use it now on my K5). That is the only shift lens that Pentax has made for the 35mm format. The lens has an expanded image circle, such that when it is shifted (in the case of the k28 a maximum of 11mm), there is a sufficient image circle size available to cover the sensor (the film in the case of what the K 28 shift was designed for) and in the case of the K20 the sensor. On shift lenses, the image circle is much larger than on the standard lenses. Given the reduced size of the APS-C sensor, this just makes it all the easier to for the image circle coverage.

The 645 lenses have a larger image circle (than either the full frame or the DFA lenses), and the 67 lenses have even a larger image circle. From what I have seen of the 645 and the 67 lenses, the mounts are just a larger or expanded mechanical version of the Pentax K mount.

The reason why the approach used by Arax (and there are a couple of other from what I understand) actually works, is that for both the 645 and the 67 lenses, the registration distance of these respective mounts is longer than that of the 35mm K mount. This allows Arax to slide the Tilt / Shift mechanism between the camera body and the 67 and 645 lenses such that the Shift and or Tilt adjustments to the lenses central optical line can be made by the user.

As indicated previously Pentax had a couple of shift lenses (and I guess I only imagined a 645 shift lens):What is nice about the approach that Arax and I think Hartabli use, is that you can specify the lens mount, thus be able to use Zeiss 645 lenses or Minolta, etc. That way you can get the focal length that you need (across the MF lenses available out there). The problem with this is that in the larger format cameras, real no wide angle lenses were made (below say 25mm) since the larger sized format "sensor" took care of that. When using this approach on the 35mm SLRs, you are somewhat stuck (on Pentax especially) with the focal lengths available and then you have the crop factor penalty for wide angle to boot. Since you are looking for 45 and 80 mm lenses, this should not affect you much at all.

Going back to your concerns, Arax should be able to work with you in terms of the projected sensor circle of the lens, which ones should work well, and if one does not, advise you as to what you will actually see.

From what I have found using the K 28 shift on both the K20 and K5 is that the greater the shift, the more the center of the lens shifts off the center of the sensor. This is obvious and as expected. So what you have is that the edge of the lens is over the sensor's center, and even a farther outlying edge of the lens is over the far edge of the sensor. The best quality light is thus falling over on the other side of the sensor. That coupled with the reversing effects of the lens, the light from the far side of the lens is entering into the lens and then being projected over to the far side of the sensor at a pretty radical angle. This really did not affect film, however digital sensors are composed of pixels. You can think of each pixel site as essentially a bucket. It likes light coming straight down into it. However, since the light is coming in at an angle (from the far side of the lens edge), the angle is pretty acute. Think of a billiard ball being shot into the side pocket with a pretty low angle. I hope you get the idea. What this boils down to is that the less you shift, the better the quality of the light getting to the digital sensor.

Hope that helps...

07-28-2012, 08:49 AM   #4
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Thanks very much for the replies guys. I think I am leaning towards the 80mm Arax at this point just to get my feet wet. I mostly shoot all of my tabletop stuff with the Tamron 90mm macro so the 80 would be fine for me. I have the Sigma 180mm macro as well but it just puts me too far away most of the time indoors.

I suppose if I am really liking what the Arax is giving me then maybe at that point I would look into other lenses with an adapter. The Mirex adapter alone costs what the Arax 80mm lens would cost. I know they make adapters for lens mounts other than Pentax. I suppose it will take a lot more research to see what people are having luck with.

Thanks again!

George

07-28-2012, 09:48 AM   #5
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Another idea and approach to this is a set of bellows and focus rails. They vary in price, and you need to look around, but a good set of bellows will also allow you to shift and tilt, along with anywhere from 1 to about 5x of magnification. The challenge is finding a unit and then changing at least the camera end mount to a lens K mount. I was given a Contax Auto Bellows that had all of this and I wound up passing it along to a local fellow forum member who was swapping the mounts.
07-28-2012, 10:05 AM   #6
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IO, I have an M42 bellows. How could you set that up to get tilt out of it? I have an M42 to PK adapter so getting my lens on the end shouldn't be a problem. I use strobes, a meter & shoot in manual mode.
07-28-2012, 10:51 AM   #7
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Unfortunately, the bellows really need to be designed with the front element being able to turn from side to side (for the tilt) and also shift from side to side (for the shift). This way, you can apply the amount of shift and tilt you find necessary. I know of three auto bellow - and they are all the same - Contax, Minolta and I believe Yashica, that offer this. You really need to look around for these, however the down side is the problem with the mounts both the lens end as well as the body end. You will have to figure out how to swap the mounts or find an adapter. The old ones can go for a lot of money, the problem is that there are very few buyers. I would think that you could strike a deal by looking. I would not pay over $100 for the bellows and a good set of focus rails.There are new ones available, however they command a very high price.
07-28-2012, 10:57 AM   #8
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Software solutions...

QuoteOriginally posted by gsrokmix Quote
Hi,

I am trying to figure out the best option for getting a T/S lens on my K20 to do mostly product shots. I have read a lot but I still need some advice on how to proceed. I have been looking into getting a Mirex T/S adapter for Pentax 645 lenses. I am confused as to what are the differences between the 645 & 67 lenses? I really know nothing about the 2 formats. Do they have different mounts? Are the lens' optical circles different sizes?

I know getting the adapter & a 45 or 80mm lens would be more expensive than getting one of the Arax lenses I see on ebay. Are the Arax lenses medium format lenses as well as the 645 lenses? I have read a couple of folks arguing whether or not you get get a pronounced tilt / shift effect on the smaller sensor camera like the K20. As I said I will be doing mostly product shots , so more tilting & swinging than shifting.

I have been in touch with the Mirex folks about their adapters and am just a little apprehensive about going the route of the adapter & 645 lens because of the expense and me not knowing how well they would work.

Does anyone have experience with both setups (the Arax & adapter plus lens)? The adapter setup seems a little more appealing for being able to use arguably better glass, and the ability have more than one focal length as I get more lenses.

Any thought or advice would be greatly appreciated.

Thanks!

George
Playing with machinery is fun, but the software is SO good now, I don't know why you'd bother really. Tried Photoshop CS 6? Perspective, distortions, and ALL the correction controls are absolutely amazing now, including the selective focus thing. You could easily mimic TS functions in software - take a wider angle photo with a higher-rez camera and crop.

IMHO.

Thanks,
Cameron

07-28-2012, 11:14 AM   #9
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IO, those are interesting ideas. I like the Novoflex but for that kind of money the adapter & lens seems more for me.

Cameron, I didn't want to have to spend any time doing PP on these kinds of images so I was hoping to get them to wher eI need them in camera.

George
07-28-2012, 05:11 PM   #10
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Post processing can add defocus effects of many types including similar to selective focus tilt effects, however, for product photography the goal is usually to use the tilt/shift/swing functions to get the entire item into focus or to decrease distortion keeping accurate lines on products. You can't use pp to create sharp focus where it didn't exist in the original image. Sharpness and polarization are two areas that pp can't do (plus pp requires time suck at the computer--Yuck!).
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