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12-27-2013, 01:01 PM   #16
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QuoteOriginally posted by Lacunapratum Quote
Imagine - some new wide angle lenses taking advantage of the shorter flange distance.
Wide angle (non-retrofocus) lenses and a short flange distance
are a good recipe for color shifts and vignetting:

https://www.pentaxforums.com/forums/76-non-pentax-cameras-canon-nikon-etc/243...ml#post2589255

12-27-2013, 01:09 PM   #17
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QuoteOriginally posted by lytrytyr Quote
Wide angle (non-retrofocus) lenses and a short flange distance
are a good recipe for color shifts and vignetting:
People tend to forget that the telecentricity requirement of the original 4/3 still has its virtues, despite sensors having gotten better at handling wide angles.
12-27-2013, 02:12 PM   #18
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I don't think short flange distances are a good idea at all for digital sensors.

While it can make it considerably easier (and cheaper) to design a good quality wide angle lens it creates a big problem for the sensor, which 'likes' to receive its light as close to perpendicular as possible. The flange distance as it is is already on the 'too short' side for a full size MF sensor.

Typically a digital sensor prefers the flange focal distance to be longer than the longest dimension of the sensor, in other words the diagonal. For non cropped 645 that is 72mm and the flange focal distance of the 645 mount is already just 70.87mm, so you wouldn't really want to reduce it any further.

If one were to go mirrorless I would see the best use for the then 'surplus' flange distance to implement a three chip sensor with ditrichroic prism. You get all the advantages of a B&W sensor combined with the advantages of a Foveon type sensor.

Last edited by lister6520; 12-27-2013 at 02:13 PM. Reason: Typo
12-27-2013, 06:40 PM   #19
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Gosh - I certainly didn't say the rear element should touch the sensor. I also didn't ask for a revival of the Mamiya 7. However, it is well known that a shorter flange distance helps with wide angle designs, e.g. lenses similar to the WATE. So far, most medium format SLRs are limited at a 20mm 24x36 equivalent, and people, including me, resort to technical cameras for shorter focal lengths. For example, I can't mount my 28mm Schneider onto my P645D or my Rolleiflex and strangely enough, it easily beats any of their lenses.

12-27-2013, 06:42 PM   #20
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... ah - 28mm Schneider Super-Digitar XL, just in case ...
12-27-2013, 06:44 PM   #21
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... or the 24mm Apo-Digitar either. Both work very well on digital sensors BTW, in spite of the previous four posters.
12-27-2013, 06:47 PM   #22
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... and those cover larger sensors, just in case anyone comments that there is not much gain in focal length, thus it would be easily imaginable that lenses of shorter focal length could be designed for the Pentax medium format sensor.
12-27-2013, 08:44 PM   #23
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QuoteOriginally posted by Lacunapratum Quote
... and those cover larger sensors, just in case anyone comments that there is not much gain in focal length, thus it would be easily imaginable that lenses of shorter focal length could be designed for the Pentax medium format sensor.
The Apo-Digitar 24mm is only intended for 36x48mm coverage,
not much bigger than the current 33x44mm "crop" sensor of the 645D.
It needs correction (e.g. with a center filter) on larger sensors,
for all the reasons we discussed earlier.

12-27-2013, 09:35 PM   #24
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First of all, none of this contradicts my earlier statement that a reduction of the flange distance would give the lens designer many more opportunities to expand in the wide angle range. Then we (you) discussed color shifts and vignetting. Center filters have little to do with color shifts and vignetting (this is natural light fall-off simply corrected optically). And the Apo-Digitar 24mm XL is perhaps a three generations old design and still works well, for me. Moreover, the 28mm Schneider Super-Digitar HM XL beats any of the currently available MFD lenses, and most would argue that the recent Rodenstocks are even better. They are retrofocus designs, but still would not fit on the P645D or on any of the current MFD SLRs. The use of all of these lenses by professionals instead of MFD wide angle lenses clearly indicates that there are benefits to shorter flange designs. I do own the 24mm XL and the 28mm XL and they are both sharper and produce less distortion than my 25mm Pentax. Moreover, they allow for a slight shift (24mm) or a humongous shift (28mm) which would be another reason for the application of such design for a digital mirrorless medium format system.

As I said - I would be extremely delighted if Pentax came out with such a camera. I guess you wouldn't. Let's wait and see...
12-27-2013, 09:39 PM   #25
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The marketing types will be going for 4k video, not mirrorless.
12-28-2013, 01:33 AM   #26
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QuoteOriginally posted by Lacunapratum Quote
Gosh - I certainly didn't say the rear element should touch the sensor. I also didn't ask for a revival of the Mamiya 7. However, it is well known that a shorter flange distance helps with wide angle designs, e.g. lenses similar to the WATE. So far, most medium format SLRs are limited at a 20mm 24x36 equivalent, and people, including me, resort to technical cameras for shorter focal lengths. For example, I can't mount my 28mm Schneider onto my P645D or my Rolleiflex and strangely enough, it easily beats any of their lenses.
Allowing the rear element to be placed closer to the sensor only helps to make extreme wide angle lenses cheaper to build, it does not make them any better. The rear element as it is in today's designs MF mounts already allows the rear element to be closer than what is prefereable for a digital sensor so reducing the flange distance won;t really help. You will just end up with the rear element being ahead of the lens flange instead of behind it if one wants to avoid the problems of low angle of incidence on the sensor.

I don't see how the fact that there aren't many ultrawide lenses for MF would change by having a shorter flange distance. It certainly has nothing to do with it not being possible. Inprinciple proportional scale up (in all dimesnions) of a 12mm for FF to MF sensor dimensions will achieve that as the ratio of diagonal to flange distance is about the same for FF. I guess the real reason may be that there is not enough demand to justify the development cost.

In any case even if for whatever reason one did want to place the rear element closer to the sensor than is allowed today because of the mirror it neither needs removal of the mirror nor a redesign of the mount to have a shorter flange distance - all one needs to do is lift the mirror out of the way when using that lens, in other words a part-time mirrorless. Ideally there would be some form of mechanical interlock to avoid inserting the mirror when the lens is down or lowering the mirror when the lens is mounted. That way you get all that you would get with a shorter flange distance without costing any versatility.

The only advantage I can see of reducing the flange distance is slightly reducing the size of the camera, something which I wouldn't think would be high on the priority list of anyone shooting in MF.
12-28-2013, 02:53 AM   #27
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QuoteOriginally posted by 672 Quote
The marketing types will be going for 4k video, not mirrorless.

If that helps move units and generate revenue, then I am all for that....especially if, and I think that recent history shows this to be the case, that allows Ricoh to build units that also are great photographic tools.

Btw., 4K and mirrorless are not in themselves in contradiction, are they?
12-28-2013, 04:27 AM   #28
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Getting the info off the chip in a timely enough manor to ditch the mirror is a massive problem. You'd have an entirely redeveloped chip wouldn't you? Huge data rates through big busses and such. Surely they'd have to use a seperate 'live view' chip.
12-29-2013, 12:45 AM - 1 Like   #29
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QuoteOriginally posted by lister6520 Quote
Allowing the rear element to be placed closer to the sensor only helps to make extreme wide angle lenses cheaper to build, it does not make them any better. The rear element as it is in today's designs MF mounts already allows the rear element to be closer than what is prefereable for a digital sensor so reducing the flange distance won;t really help. You will just end up with the rear element being ahead of the lens flange instead of behind it if one wants to avoid the problems of low angle of incidence on the sensor.
Current lens designs for MF digital backs proof you wrong. The Rodenstock 23mm/5.6 S-Digaron leaves 16mm from the rear element to the sensor surface - certainly not enough for the Pentax mirror. This lens in fact can be had with focusing mount and theoretically could be adapted to a mirrorless MFD of short mounting distance. Few of the lenses for MF digital backs, even the telecentric designs, would fit a digital SLR with mirror, unless they are of longer focal length, and with these designs compactness certainly is not an issue.

There are also issues of convenience. Returning to the mirror-up design in the 21st century would certainly have commentators and online blogs scratch their pixels. Moreover, saving weight and saving cost does make a difference when one considers the cost for these lenses (e.g. $5K for the Pentax, $8K for the Rodenstock). And the judge is still out as to which designs would be better. Neither you or I have designed the new generation of lenses for the putative mirrorless P645Dii.

As I said - I didn't propose that the new digital P645Dii should become a Sony A7r on steroids. I'd hope Pentax would do their homework and calculate some excellent wide angle lenses in advance. Perhaps they'll also add a global shutter or a front-end shutter to deal with the shuttershock issue the Sony suffers from. I bought a dozen adapters for the Sony mount, but last minute decided to wait for generation II of the camera body. These mirrorless camera manufacturers are incredibly creative and every generation seems to introduce a bunch of innovations.

I am also not proposing that the Pentax K-01 was the cat's pajamas. An unsuccessful design that didn't save weight and had few if any advantages. I'd hope Pentax learns from this and other mistakes and brings something truly innovative on the market, designed for the photographers, as they did in the past.

I simply felt intrigued by the news that Pentax/Ricoh would come up with something new and different for the 645Dii and I am hoping it's mirrorless. You don't. Let's wait and see.
12-29-2013, 01:19 AM   #30
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QuoteOriginally posted by Lacunapratum Quote
I am also not proposing that the Pentax K-01 was the cat's pajamas. An unsuccessful design that didn't save weight and had few if any advantages. I'd hope Pentax learns from this and other mistakes and brings something truly innovative on the market, designed for the photographers, as they did in the past.
The main problem of photographical industry is, no matter how advanced and progressive technology is mainstream buyers are to conservative. Every one forgets that IQ should come first design of camera second. You can go in two directions in design; K-01 unconservative ergonomic (yes it is ergonomic) is one side of spectrum and Nikon DF traditional-retro unergonomic is the other. Of corse there are cameras in the middle like Olympus OM-D E-M5 and Fuji X Series combine both sides of spectrum.
I think Pentax/Ricoh should go balls to the wall and make unconservative design cameras, especially in MF class.

Last edited by i83N; 12-29-2013 at 01:25 AM.
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