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02-06-2015, 08:34 AM   #1
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True MF

So as pentax finally making FF can we hope for true MF sensor in 645 line? If I recal it 645D and Z sensor (especially D) are just two apc-s sensors put together side by side and true MF is two FF sensors side by side.

02-06-2015, 08:43 AM - 1 Like   #2
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QuoteOriginally posted by i83N Quote
So as pentax finally making FF can we hope for true MF sensor in 645 line? If I recal it 645D and Z sensor (especially D) are just two apc-s sensors put together side by side and true MF is two FF sensors side by side.
Well... not quite from what I remember... true MF is slightly larger than 2 FF senzors next to each other...
Film size comparison attached.
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02-06-2015, 09:03 AM - 2 Likes   #3
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What's a "true" medium format? As mrNewt shows, there are lots of different frame sizes projected onto a 120/220 roll of film and all are called "Medium Format". In the digital age, I guess we want to define Medium format as either a cropped version of the 6x4.5 or all of it. What happens when sometime in the future we get a 6x6 or 6x7 sized sensor.
02-06-2015, 09:05 AM   #4
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QuoteOriginally posted by tuco Quote
What's a "true" medium format? As mrNewt shows, there are lots of different frame sizes projected onto a 120/220 roll of film and all are called "Medium Format".
I assume he is referring to the 645 MF... which is larger than 2 35mm slides put next to each other when considering its "true" size.


Last edited by mrNewt; 02-06-2015 at 09:58 AM.
02-06-2015, 09:11 AM   #5
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QuoteOriginally posted by tuco Quote
What's a "true" medium format?
This is completely subjective on my part, but in my mind medium format has always been anything on a roll that's bigger than 35mm. I've always considered sheet film to be large format.
02-06-2015, 09:15 AM   #6
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QuoteOriginally posted by Parallax Quote
This is completely subjective on my part, but in my mind medium format has always been anything on a roll that's bigger than 35mm. I've always considered sheet film to be large format.
Even though the same roll is used, it's probably better to think of the different formats by the systems they are loaded in. Technically, yes, a 645 Mamiya, a 6x6 Hasselblad and 6x7 Pentax are all MF, but the way they are used and their output can't really be compared apples-to-apples.

QuoteOriginally posted by i83N Quote
So as pentax finally making FF can we hope for true MF sensor in 645 line? If I recal it 645D and Z sensor (especially D) are just two apc-s sensors put together side by side and true MF is two FF sensors side by side.
Depends on the camera in question, but full-frame (645) MF is considered to be around 40.5 x 56mm. Even if we were to put two 35mm sensors side-by-side, we would "only" have 36x48mm, which is quite a bit smaller. And of course it's not as simple as putting anything "side-by-side", the Sony 51MP sensor is a completely original design that likely doesn't even borrow from the D800 since the pixel pitch is different. Sony does have to use mask stitching to achieve a sensor of this size and resolution, all while maintaining the small production process required for high DR, so it's not easy to manufacture even as it is.

There are only a few companies in the world that actually make computer chips, so Pentax is wholly dependent on Sony (or others) for whether or not anything bigger will come out, but how prepared Pentax is to bet on something another company may or may not do is out the scope of our knowing. For now we can only speculate, but it does seem that Pentax isn't writing the possibility off entirely, since the 645Z is exactly the same size as the D, which is the same size as what a film Pentax would be... unless they plan on putting out a full 645 sensor version, there is no reason why they should have kept the camera this large if they only ever expected to utilize a crop sensor.

Last edited by Kolor-Pikker; 02-06-2015 at 09:43 AM.
02-06-2015, 09:42 AM   #7
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QuoteOriginally posted by mrNewt Quote
Well... not quite from what I remember... true MF is slightly larger than 2 FF senzors next to each other...
Film size comparison attached.
What he said!

Medium format is a loose term and in the modern sense for film includes all formats that can be serviced with 120/220 roll film with the smallest being 645 (6cm x 4.5cm) and the largest being 6cm x 12cm. Digital medium format falls a little short of 645 and far short of the rest of the traditional MF range. I don't know of any maker who make a camera with a true 645 sensor, much less a 6x12*.

I believe the largest is about 5.4cm x 4cm which is somewhat larger than two FF sensors side-by-side. The 645Z is 4.4cm x 3.3cm.


Steve

* There are scanning MF backs for use with view cameras that cover a larger format, but they are a special case and must be used tethered to a computer.

Last edited by stevebrot; 02-06-2015 at 09:50 AM.
02-06-2015, 09:42 AM   #8
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QuoteOriginally posted by Kolor-Pikker Quote
... unless they plan on putting out a full 645 sensor version, there is no reason why they should have kept the camera this large if they only ever expected to utilize a crop sensor.
I think the image circle of the new 645D/Z lenses tells you just how much they are looking at the future size of the 645 sensor. And when the 645D came out, Pentax did not have the deep pockets of Ricoh. So to keep the same registration distance of the film camera meant utilizing exiting legacy glass which relaxed the pressure to come out with a completely new line of lenses for the 645D.

02-06-2015, 09:53 AM   #9
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QuoteOriginally posted by tuco Quote
I think the image circle of the new 645D/Z lenses tells you just how much they are looking at the future size of the 645 sensor. And when the 645D came out, Pentax did not have the deep pockets of Ricoh. So to keep the same registration distance of the film camera meant utilizing exiting legacy glass which relaxed the pressure to come out with a completely new line of lenses for the 645D.
Even with keeping the registration distance the same, there is a lot of bulk in the other two dimensions that could have been shaved off, while still keeping compatibility with the larger lenses.

And what about the 4cm/1.6" distance between the sensor plane and the backside of the camera? Certainly modern electronics don't need a 4x14x10cm large cavity in which to fit?
02-06-2015, 09:54 AM   #10
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QuoteOriginally posted by Kolor-Pikker Quote
the 645Z is exactly the same size as the D, which is the same size as what a film Pentax would be... unless they plan on putting out a full 645 sensor version, there is no reason why they should have kept the camera this large if they only ever expected to utilize a crop sensor.
There are a full flaws to this logic, but the core truth is that the registration distance is the same between the Pentax 645 film cameras and their digital cousins. As with the FF digital vs. 35mm film cameras, the actual camera size will vary due to design/feature constraints.


Steve

Last edited by stevebrot; 02-06-2015 at 10:04 AM.
02-06-2015, 10:01 AM   #11
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QuoteOriginally posted by Kolor-Pikker Quote
Certainly modern electronics don't need a 4x14x10cm large cavity in which to fit?
LOL...ROFL...

Have you looked at the flagship Nikon or Canon FF products lately? The optical path is a very small portion of the bulk there. In the digital MF SLR world, the Leica S and Pentax 645 are the slim and trim models. I can assure you that the space behind the sensor plane is not empty.


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02-06-2015, 11:33 AM   #12
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QuoteOriginally posted by stevebrot Quote
LOL...ROFL...

Have you looked at the flagship Nikon or Canon FF products lately? The optical path is a very small portion of the bulk there. In the digital MF SLR world, the Leica S and Pentax 645 are the slim and trim models. I can assure you that the space behind the sensor plane is not empty.


Steve
...maybe, even in a smartphone 70-80% of all internal space is just the battery, if a complete $600 phone can stick all processing and memory on a stick about the area of a post-it note, it would be disappointing if the same couldn't be done in the camera world. In any case, even the 1Dx and D4 have significantly lower volume, if not mass, than the 645Z, although the latter doesn't have a vertical grip.

One simply has to look at the a7R to know that you can compress things down quite a bit, electronically it's not dissimilar from any other kind of camera, although pro bodies have such an over-abundance that they can expand to multiple processors for more efficient processing.
02-06-2015, 11:48 AM   #13
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QuoteOriginally posted by Kolor-Pikker Quote
One simply has to look at the a7R to know that you can compress things down quite a bit,
I was thinking specifically about the A7 when I typed my comment. I suggest that you look at the tear-down of the A7R and A7ii to see just how much stuff sits behind the sensor.

LensRentals.com - The A7R teardown: A look inside Sony's awesome full-frame mirrorless camera

LensRentals.com - The A7II Teardown: A Look Inside Sony's New Camera

Space inside most sophisticated AF cameras is at a premium.


Steve
02-06-2015, 12:09 PM   #14
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IBIS takes a lot space. And the bigger the sensor the more space it will require.
With Pentax is also the issue with the flange distance since they try and offer support for their legacy lenses. Also, the mirror size and the prism size affects the body size. Then you also want all the quick controls on the body rather than spend hours going trough the menus and such... all these adds to the bulk and end result.
If Pentax will drop the current mounts and mirror, they will magically get smaller as well .
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