lens confusion..

hello all, just a question. Are modern pentax lenses made for a crop sensor or full frame??
i want to buy a 50mm prime. Will the DA 50mm 1.8 be an actual 50mm or a 70+ mm??
if the latter, the DA 35mm 2.4 AL will be the closest perspective to a 50mm on a full frame right?

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just a newbie with a good eye

The focal length of a lens is as marked, regardless. However, the coverage, that is, the size of the image circle the lens projects, depends on the format it is intended for. For a given format, the focal length needed for a "standard" lens varies, usually taken to be the measure of the diagonal of the frame.

So a "standard" lens for a 35mm film camera is technically a 43mm, but more usually 50mm.

The "standard" lens for APS-C is about 35mm, so you are correct that it will show a similar image to a 50mm lens on a 35mm film camera.

On APS-C, the 50mm is a short telephoto, just about right for portraits. The 55mm is almost exactly equivalent to the 85mm so popular as a portrait lens on 35mm film.

Hope that helps!

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Best regards, John

I admit to being a bit confused by the current Pentax range as well. In general I believe that most of the new DA lenses are only suitable for APS-C digital models, so if you put them on a film SLR then you would see a progressive darkening from a third or so in from the edges to black at the edges (thanks to John in an earlier thread for explaining this).

But I have seen references to this or that DA lense actually covering a 35mm film frame (ie so-called FF digital model). But I am unclear on how this is specified in the lens name?? Is it just the Limited range? Any info much appreciated,as if I want the option to buy a FF camera in the future then I'd better not buy any more cropped DA lenses!

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My Guides to the Pentax Digital Camera Flash Lighting System : Download here from the PentaxForums Homepage Article .... link
Pentax K7 with BG-4 Grip / Samyang 14mm f2.8 ED AS IF UMC / DA18-55mm f3.5-5.6 AL WR / SMC A28mm f2.8 / D FA 28-105mm / SMC F35-70 f3.5-4.5 / SMC A50mm f1.7 / Tamron AF70-300mm f4-5.6 Di LD macro / SMC M75-150mm f4.0 / Tamron Adaptall (CT-135) 135mm f2.8 / Asahi Takumar-A 2X tele-converter / Pentax AF-540FGZ (I & II) Flashes / Cactus RF60/X Flashes & V6/V6II Transceiver

The focal length of 50 mm is 50 mm regardless of whether it's APS-C, 135 or 645/6x6/6x8/6x9/6x12/6x17/10x8,5x4, 110 or 126 etc etc...

Yes, the 35 DA/FA on a K-5 would give the same view as a DA/FA50 on a Z-1, just as a K-5 +DA*55 would give the same view as the wonderful FA*85 on the Z-1....

Likewise 35mm on APS-C gives the same view as 75/80 mm on a 645 film camera (6x4.5/6x6).....a Pentax or Mamiya 645 45/50/55mm would be a wideangle....

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AKA Welshwizard/PWynneJ
Assorted Pentax/Nikon/Mamiya stuff

The explanation I read was that the format covered by Pentax DA lenses was generally a generous APS-C, so this makes allowance for movement of the sensor as it shifts for SR. This is not the same as them covering a full frame area.

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Best regards, John

Ah ha - a good point John, for this reason Pentax's 'cropped' lenses have to project a slightly bigger image circle than some other brands. And lets not forget also the 'Horizon Adjustment' and 'Auto Horizon Correction' features!

Acutally, I think I noted when buying the camera that the Pentax sensor is bigger than the original APS film frame anyway, a little bit bigger??

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My Guides to the Pentax Digital Camera Flash Lighting System : Download here from the PentaxForums Homepage Article .... link
Pentax K7 with BG-4 Grip / Samyang 14mm f2.8 ED AS IF UMC / DA18-55mm f3.5-5.6 AL WR / SMC A28mm f2.8 / D FA 28-105mm / SMC F35-70 f3.5-4.5 / SMC A50mm f1.7 / Tamron AF70-300mm f4-5.6 Di LD macro / SMC M75-150mm f4.0 / Tamron Adaptall (CT-135) 135mm f2.8 / Asahi Takumar-A 2X tele-converter / Pentax AF-540FGZ (I & II) Flashes / Cactus RF60/X Flashes & V6/V6II Transceiver

thanks for the helpful comments! i finally understand now hehe

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just a newbie with a good eye