[Dmaxx]

Just recently ordered an MX, itching to try film. How will the focal length be for the Tamron AF 28-75mm f/2.8 XR Di for 35mm film body? is it still 28-75mm? since we always multiply the magnification factor of the apsc when using film lens to digital body, would it be applicable vice versa (dividing it by the magnification factor). Also is it only the 3rd party brand that offer a new digital lens with aperture ring, would like the option of being able to swap film and digital bodies with my lens. Plan on buying ultra wide lens from either Sigma 10-20mm and Tamron 10-24, instead of Pentax 12-24 because of the aperture ring option.

Regards

[Adam]

Focal length is focal length, it never changes (even on digital). On film, that lens will give you a diganal FOV of about 75-30 degrees. And yes, you will need a lens with an aperture ring if you plan on using it with the MX.

[redrockcoulee]

The 28 is a wide angle similar to a 18 or 19mm on your dSLR and the 75 is a small telephoto sort of like using a 50 in digital. The comments that a 28 is a 28 on all formats is correct but how it seems is different and if you never used more than one format it is hard to understand that truism. My wife has the 10-20 Sigma and it is for all practical purposes unusable on my film camera as the image is not large enough to cover the entire film surface, you will end up with severe vignetting. 10 or 12 would be extremely wide on a film or full frame camera, I have the 17-28 fisheye which is more like a 15mm at the widest end and seldom use it just too wide for me.


I shoot a K-r, a 35mm film camera, a Hasselblad and three formats of large format cameras. Sometimes I look at lens equivalencies like if I think I need a wider lens for 5X7 what would give me the same as the 90mm on a 4X5 but generally I call my 210 mm lens a 210 even though it is a slightly longer than normal on one format, the normal on a second format and a wide on the third it is still the same lens. Same as the 35 DA 2.4 is a normal on my K-r and a mild wide on the MZ5n but is will always be a 35mm lens and I never think of it as a 35 X 1.5 = 52.5 mm. It is a 35. What you need to know with wider lenses is do they cover film/full frame and of course it must be compatible with the MX.

[Dmaxx]

Thanks Adam, and redrockcoulee. I see, so only the field of view change, no actual magnification is being done, after all these years i was made to believe otherwise . Hmmm no wonder most of the widest 35mm film lens i see stop at 15mm, and only just recently we have the 8mm, and 10mm. So the only usable range of the wide angle lens will probably 15-20 for the sigma/tamron on my MX, now im having second thoughts on buying ultra wide lens

[HGMonaro]

How will the focal length be for the Tamron AF 28-75mm f/2.8 XR Di for 35mm film body?

great range for a general purpose lens.

[TomB_tx]

Be aware that many of the lenses designed for the smaller digital sensors won't cover the full 24x36 frame of a film camera. With their smaller image circle (for the same focal length) you may have dark corners at least on the resulting film image. I don't know about the specific lenses you are considering, but this problem is often overlooked when going "back" to film.

[Stratman]

Here is an example of the difference between 28mm on APS-C digital, and 28mm on film. These shots were taken from the exact same spot. Will give you an idea of the difference..

Digital



Film

[Dmaxx]

Thanks TomB_tx, Stratman based on the picture itself not only the field of view change also some magnification did happen hmm..

[Philoslothical]

The "magnification" is an illusion. Both images are being shown at the same resolution, so the narrower field of view appears to be closer. Since film doesn't use the same resolution scale, it would depend on the scanned resolution of the print, compared to the full resolution of the digital image. Both images above have been resized down considerably (presumably, since film is usually scanned quite high, 300 dpi I think?), so there's no real comparison to be made.