[Paul MaudDib]

If Pentax won't make a FF 35mm DSLR, I highly doubt they would make a full frame 645D. The same logic applies - they are investing in lenses that (while they can be used full frame) are designed with crop sensors in mind.

You never know and I would be delighted to be proven wrong, but I wouldn't get my hopes up.

[Yamanobori]

I think they are doing two things. First, they are keeping their options open as there is no standard size for a MFD sensor--there is no such thing as a crop sensor. Second, they are keeping the option open for purchases from their film camera customer base.

[Paul MaudDib]

That's a copout. There are plenty of standard sizes for medium format. 645 is one standard, 6x6 is another, 6x7 is yet another, 6x9 is another still. Lenses are designed with one of those sizes in mind, and people mentally reference cropping from there. You can even see it from Pentax - they made sure the new 90/2.8 covers the full 645.

[Yamanobori]

That is funny. I always thought the format was to do with the image area and nothing to do with the size of the image circle. A 300mm large format lens is a 4x5, 5x7, or 8x10 lens? I wonder if my m4/3 camera becomes crop sensor when I mount a 35mm lens vs. a native m4/3 lens?

BTW, you are simply listing film standards. There are now digital standards.

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Last edited by Yamanobori; 02-10-2012 at 05:02 PM.

[Makten]

A 300mm large format lens is a 4x5, 5x7, or 8x10 lens?

Depends on the image circle, yes. But of course you can use it on a smaller format than intended (you don't make a 300 mm lens with a larger image circle than necessary, I can assure you).

A smaller image circle can actually give a little bit higher (center) resolution, so there are benefits with using an as small image circle as possible. But you'll lose corner sharpness and get worse field curvature as well.

[itshimitis]

That's a copout. There are plenty of standard sizes for medium format. 645 is one standard, 6x6 is another, 6x7 is yet another, 6x9 is another still. Lenses are designed with one of those sizes in mind, and people mentally reference cropping from there. You can even see it from Pentax - they made sure the new 90/2.8 covers the full 645.

Yamanobori was perhaps referring to the sensor size (MFD) which does vary according to manufacturer. Pentax 645D is 44 x 33. Mamiya's, Hassleblad's and Phase's are different. Not by much but they are generally bigger. There is also the possibility that Pentax themselves might want to vary the size of the sensor in the future.

[Digitalis]

A 300mm large format lens is a 4x5, 5x7, or 8x10 lens?

A normal lens for a 4X5 is 150mm*, since 8X10 is twice the size in film area a 300mm lens is required to produce a similar FOV - but the FOV will be the only thing in common between the different lens used for each format.

To get the same FOV as a 90mm lens on 35mm camera on 8X10 format you have to use a 900mm lens - or a 600mm lens on a 4X5 camera.

* which produces a FOV of a 45mm lens 35mm terms - so roughly the same FOV as the Sigma 30mm f/1.4 on an Pentax APS-C camera body

[Yamanobori]

OK large format shooters, show me a modern 300mm f/5.6 4x5 lens that does not cover 8x10 and vice versa. I am not talking about FoV. Just a plain old 300mm from Rodenstock or similar--not a telephoto design BTW. It was not long ago that you bought large format lenses based on the angle of coverage--eg. 72 degrees, regardless of focal length. This is how Rodenstock lines line like Sironan-N and Sironar-S are defined, by the angle of coverage--if I remember correctly, 72 and 75 degrees, respectively.

[Yamanobori]

Yamanobori was perhaps referring to the sensor size (MFD) which does vary according to manufacturer. Pentax 645D is 44 x 33. Mamiya's, Hassleblad's and Phase's are different. Not by much but they are generally bigger. There is also the possibility that Pentax themselves might want to vary the size of the sensor in the future.

Leaf, Phase, and Hasselblad all have 40MP sensors that are 44x33, some are the same as the one in the Pentax. The 22MP and 33MP Leaf/Phase sensors are a little bigger. And then the big sensors are very close to 6x4.5.

In an irony of history, APS-C was first a film format.

[Digitalis]

OK large format shooters, show me a modern 300mm f/5.6 4x5 lens that does not cover 8x10 and vice versa.

I have never heard of a lens designed for 8X10 that couldn't cover 4X5, Rodenstock and Schneider did produce lines of lenses that were specifically designed for 4X5 - it was possible for these lenses to be used on 8X10 format cameras however, camera movements were severely limited* because of the smaller imaging circle. Both makers also make lenses with even smaller imaging circles that are designed for medium format backs, and are incapable of being used with film backs bigger than 6X4.5cm - and with certain lenses even that format is too big.


* trust me, it is essential to have camera movements on 8X10.

[NotaxPen]

90mm on a 645D (44x33) has an equivalent angle of view to:

135: 71mm
APS: 46mm
645: 115mm

OK, that's a little closer to what I need. If I can focus close enough for a tight headshot without distorting the face, I suppose that would work.

I keep forgetting that I can probably crop more out of a 645D image than my 645n.