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04-15-2013, 01:15 PM   #1
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Medium Format Lenses + Q

Is anyone out there currently using their Q with medium format lenses? If so, how is it working out, what has the experience been?

04-15-2013, 01:25 PM   #2
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Just FYI, the Pentax materials warn against trying to use medium format lenses on the Q.
04-15-2013, 03:03 PM   #3
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QuoteOriginally posted by Docrwm Quote
Just FYI, the Pentax materials warn against trying to use medium format lenses on the Q.
Oh, now I am so gonna try it!

The focus peaking should be good for the tilt adapter, too!
04-15-2013, 03:10 PM   #4
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Not exactly using, but I've tried it a little.

My CZJ Sonnar 180/2.8 is pretty soft (and stupidly large and heavy). Not really surprising. I'll have to try the even larger CZJ Sonnar 300/4 some time.

My Pentax 645 A 120/4 macro is ok, but too large and heavy for a lens without a tripod foot. (Might actually be good if you rig up some support.)

My Pentax 645 FA 75/2.8 seemed pretty good in a quick test, and isn't even particularly large. (Large on the Q of course.) I might find the time to test it a bit more, but it's longer than I tend to want.

04-15-2013, 03:21 PM   #5
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QuoteOriginally posted by Docrwm Quote
Just FYI, the Pentax materials warn against trying to use medium format lenses on the Q.
Well, I wonder if that's because of the Q-K converter attachment foot loading capacity, or something else. A little forethought would suggest the use of a lens attachment, rather than the converter's, for heavier lenses. One would have thought that resolution wouldn't have been an issue.
04-15-2013, 03:31 PM   #6
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Given that ultimate enlargement from medium format negatives may be lower, it may be that the resolution is lower than 35mm lenses. I have been wondering about this a littke
04-16-2013, 02:45 AM   #7
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All the talk of diffraction and pixel size and so on just had me wondering if these lenses have properties that are exposed by the Q that wouldn't be on a larger format camera? In the end the real world examples tell the tale but I don't have a Q so I don't have any testing to do.
04-16-2013, 03:23 AM   #8
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QuoteOriginally posted by littledrawe Quote
All the talk of diffraction and pixel size and so on just had me wondering if these lenses have properties that are exposed by the Q that wouldn't be on a larger format camera? In the end the real world examples tell the tale but I don't have a Q so I don't have any testing to do.
How do they perform on a Pentax DSLR compared to film?

From my experience film in 35mm format is about a 10MP at best resolution. It may be better with the slower films used in medium format but lets say it can do double the resolution.

That gets a 35mm frame to 20 MP or about 3600 pixels in 24 mm for a pixel pitch 6.66 microns

The Q has a pixel pitch of about 1.75microns

It has about 4 times the resolution at the sensor.can the lens deliver?

04-16-2013, 05:20 AM   #9
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Another issue might be loss of contrast with all the unwanted light bouncing around in the long register adaptors.
I found that making K to M43 adaptors. The bore needs to be as large as possible all the way and the internal coating needs emissivity close to unity.
On the other hand the Pentax 110 lenses have an image circle of same size as M43 and a short register so the adaptors work well, even though those little lenses may not be as high quality.
04-16-2013, 05:52 AM   #10
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QuoteOriginally posted by wombat2go Quote
Another issue might be loss of contrast with all the unwanted light bouncing around in the long register adaptors.
Yeah, I thought this would be the main thing. And possibly resolution, because the Q sensor is so dense.

It could also just be mechanical, if you have a very big and heavy lens you might risk damaging the mount?
04-16-2013, 06:04 AM   #11
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QuoteOriginally posted by wombat2go Quote
Another issue might be loss of contrast with all the unwanted light bouncing around in the long register adaptors.
I found that making K to M43 adaptors. The bore needs to be as large as possible all the way and the internal coating needs emissivity close to unity.
On the other hand the Pentax 110 lenses have an image circle of same size as M43 and a short register so the adaptors work well, even though those little lenses may not be as high quality.
I just put a bit of on old (black) sock in the adapter. Seems to work well enough.
04-16-2013, 06:29 AM - 1 Like   #12
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QuoteOriginally posted by drougge Quote
I just put a bit of on old (black) sock in the adapter. Seems to work well enough.
Here is my M43 adaptor bored as large as possible and coated with 2 coats Krylon Camo matt black.
The sheen from the necessary step down to M43 bore can be seen.
Since then I am using Protostar self adhesive telescope flocking for bores and lens boards. It is really black, excellent stuff.
When I get time i will cut a little annulus of flocking and cover over that step. I think that will improve the adaptor.
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04-16-2013, 01:44 PM   #13
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QuoteOriginally posted by Lowell Goudge Quote
That gets a 35mm frame to 20 MP or about 3600 pixels in 24 mm for a pixel pitch 6.66 microns
The Q has a pixel pitch of about 1.75microns
It has about 4 times the resolution at the sensor.can the lens deliver?
I'm going to need to see some kind of drawing or something to make this make sense, I suppose I am more of a visual learner. Off to the internets to see what I discover.
04-16-2013, 03:10 PM   #14
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Well, more testing suggests that at least the SMC Pentax 645-FA 75mm f/2.8 is sharp enough for the Q. (Of course, it's probably Pentax's sharpest 645 lens (same as the A version), possibly excluding the new made for digital ones, so this is not terribly surprising.)

It's fine at f/4 and f/5.6, acceptable wide open and up to maybe f/11 (where it is naturally softer than wide open). (Quite a bit of PF wide open though.)

These are at 5.6 and 6.7, but not because of any great thought going into those choices. (Full size available on flickr.)

04-16-2013, 03:58 PM   #15
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QuoteOriginally posted by littledrawe Quote
I'm going to need to see some kind of drawing or something to make this make sense, I suppose I am more of a visual learner. Off to the internets to see what I discover.
Imagine comparing the 12MP K-r and the 12MP Q camera. They both have the same size images that they output, the same number of pixels. But the Q has a much smaller sensor. Each pixel is a little node on the sensor that detects light, which means that on the Q they must be smaller and packet closer together. Otherwise you can't get the 12MP onto a smaller area. The second part is that lenses have a certain resolution of their output. If he camera sensor has the same resolution, it will be optimally sharp. But if the sensor has a higher resolution than the lens, the lens will appear to be not sharp, because the sensor is detecting more fine detail than the lens can deliver. So a lens that looks sharp on the K-r, might look less sharp on the Q. But it might look perfect on a 6MP APS-C camera.
Same principle for medium format lenses. Btw, the D800e, with its high MP count, is facing this problem because a lot of lenses that were perfectly decent on older models now no longer look as good on this camera. So if you make a sensor with much higher resolution, you also need to make lenses that match it.
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