Is 35mm film really 24mm x 36mm?

[james_ogara1]

Sounds like an odd question. I never questioned the assertion that

135 film has a 2 x 3 aspect ratio.

 

But when I load a frame into my Coolscan 4000 ED, and try to line up a

cropping rectangle that has been fixed at 2400 x 3600 pixels (300 dpi

at 8 x 12) it cuts off a bit lengthwise. If I capture all of the long

side, I also end up bringing in some of the unexposed edge on the

narrow side.

 

What's up with that?

 

(Camera = Nikon F-2 and F-4.)

[jimvanson]

James -- I realize that digital is perfect -- that it can do everything -- that we should trust it over everything -- BUT I gotta ask did you go ol' fashioned linear route and measure a frame of film with a ruler?

[markci]

35mm film doesn't have any aspect ratio -- the window in front the film in your camera does. It's not inconceivable that there is some variation.

[stephen hazelton]

Maybe your pixels aren't square!

 

FYI- the mask on film printers that the one-hour labs use, cannot print an entire 35mm negative. Maybe they're actually masked down to a slightly smaller size. Or maybe cameras actually make a slightly bigger image. Ditto with the filmholder on my enlarger. I remember once upon a time having a neat train shot with locomotive at one edge, caboose at the other. Lab could shift if and print one or the other, but not both. Arrrrggh!

 

There's either some variation in the cameras or in all the other doohickies that use film.

[steve_dunn2]

<p>Well, I suppose <em>somebody</em> has to step up and take a ruler to a piece of film ...</p>

 

<p>I measured a frame shot by my old Miranda Sensomat RE; to within the accuracy of my eyesight, it's exactly 24mm by marginally less than 36mm (but much closer to 36 than to 35). Ditto for a frame shot by my old Canon EOS Elan II. I haven't bothered to measure a frame shot by my current Elan 7E. The viewable area of the mounts that some of my slides are in is 23mm by very, very slightly less than 35mm.</p>

[stwrtertbsratbs5]

There are a number of older cameras (Robots and Zeiss Ikon Tenax) that produce 24mm square images on 135 film. So I agree - the camera is the window that determines the size.

[mendel_leisk]

Just finetuning the focus seems to change the x to y proportions a bit, when I'm scanning.

 

Plus, with slides, there's the factor of the frame being skewed in the holder to contend with.

 

Just loosen up a bit, auto crop to get as big a clean rectangular rectange as possible without catching the holder or slide, and forget-about-it.

 

I got hung up on having all my file pixel dims. the same, and some proportion, on my last project. It's just cropping more than you need.

[richard_cochran]

With a scanner, I suspect your pixels may not be exactly square,

and/or the scanner may not cover the complete frame. Since the

scanner uses a different mechanism to determine the vertical distance

between pixels than it uses to determine the horizontal

distance, it's not inconceivable that the two mechanisms

are slightly out of kilter with each other. The fact that

refocusing the scanner can change the ratio a bit boosts this

theory.

<p>

I just measured a frame from my Nikon F3, and it's exactly

24mm x 36mm to the limits of my vision, within at worst a few

tenths of a millimeter. I'd expect all the Nikon F series to have

fairly tight tolerances. But the original poster's was asking

for 2400 x 3600 pixels, which means a precision of better

than 1/100 of a mm, which would mean a one pixel error

is getting dangerously close to the precision that the film

can resolve. Halation of bright light sources can easily

make a bit of the image exceed the nominal frame boundaries.

[berk_sirman2]

I remember reading in the Leica forum that image area CAN exceed 24X36mm when using extreme wide non-retrofocus lenses due to the angle which light hits the film. This can only happen on rangefinders though since SLR mirrors would not allow such lenses.

[x]

My Horizon is 58mm x 24mm is I remember correctly and an Xpan is broadly similar. It's the camera, not the film which determines the frame size !

[janusz_mrozek]

Somewhere in the distant past, I learned that the true dimensions were 23.5mm x 35.3mm. But I can not find a good source for this now; the best source I can find is:

 

http://www.imagingspectrum.com/cgi-local/SoftCart.exe/filmscanners.html?E+scstore

 

Look in the specs for the first scanner.

 

Any idea as to where these dimensions came from, for what equipment they are valid, etc.?

[bill_tuthill]

Back when I was debating Kennedy McEwen about Coolscan cropping,

I measured my negatives, and most of them had frames slightly larger

than 24x36mm. More like 24.5 x 36.5 mm. It does depend on the

camera's shutter design.