50mm=35mm on film?

Joined: 11 Oct 2005 Posts: 176 Location: philly

what do they mean with the formats on cameras, like a digital slr 50mm lens equals a 35mm on film cameras?

Joined: 02 Jan 2007 Posts: 190

It's due to the smaller sensor size than the conventional 35mm film.

The sensor therefore has a magnifying factor of around 1.5x depending on the camera and make. This then gives us the 35mm equivalent focal length for our dSLR's.

35mm (focal distance, not film size) x 1.5 (sensor mag factor) = 52.5mm (35mm film focal distance equivalent)

hope this helps.

Joined: 18 Nov 2006 Posts: 288

You can't use lenses designed for digital on 35mm cameras because they will vignette - they won't cover the entire frame. You can go in the other direction, however, and this is where the "crop factor" takes affect. A 50mm lens designed for a 35mm camera will be something like a 75mm lens on a digital because the digital crops the frame to about 2/3 the size of a 35mm camera's frame.

Posted: Sun Feb 25, 2007 3:16 pm

Hoosiershooter wrote:

You can't use lenses designed for digital on 35mm cameras because they will vignette - they won't cover the entire frame. You can go in the other direction, however, and this is where the "crop factor" takes affect. A 50mm lens designed for a 35mm camera will be something like a 75mm lens on a digital because the digital crops the frame to about 2/3 the size of a 35mm camera's frame.

I'm sure you know this Hoosier, but your post reads a bit ambiguously.

A 50mm lens is a 50mm lens, designed for digital, 35mm film, 645 or any other format. The field of view recorded is decided by the size of the recording medium (film or CCD). Since most DSLRs use sensors which are smaller than the old 35mm film frame, but are used as direct replacements for 35mm cameras, we end up with the "crop factor".

In fact, APS-C is just another format like any other. The field of view would be exactly the same if you were using one of the few SLRs which were produced for APS film.

Joined: 11 Oct 2005 Posts: 176 Location: philly

so an old 50mm lens on a new digital slr would be 75mm, and when they talk about this they r talkin about how big the photo will be, not the outside lens right

Joined: 18 Nov 2006 Posts: 288

den9 wrote:

so an old 50mm lens on a new digital slr would be 75mm, and when they talk about this they r talkin about how big the photo will be, not the outside lens right

No, it would still be a 50mm lens. It would have an equivalent angle of view that a 75mm lens would have on a 35mm camera.

Joined: 11 Oct 2005 Posts: 176 Location: philly

ok im back for more questions about this

an older 80-200mm lens, would that have the crop factor on a digital?

only the new digital lenses like dx have advertised focal length for digital right?

Posted: Fri Mar 23, 2007 9:51 pm

den9 wrote:

ok im back for more questions about this

an older 80-200mm lens, would that have the crop factor on a digital?

only the new digital lenses like dx have advertised focal length for digital right?

The focal length of the lens is just that. An 80-200 zoom is an 80-200 zoom, no matter what it was made for.

I could take a Pentax 67 105mm lens (designed for 6"x7" medium format film) and mount it via an adaptor on my K10D. It would produce exactly the same field of view as a Sigma 105 DG Macro designed for a crop sensor digital.

Focal length does not change with crop factor. All that is happening is you are cutting out a smaller section of the same image. It's like taking all your film negatives, cutting out a section from the middle and blowing that up to full size.

Joined: 11 Oct 2005 Posts: 176 Location: philly

i still dont understand how a 50mm prime lens is a 75mm on a dslr, is it becuz it has a larger sensor so its getting cropped?

Posted: Sat Mar 24, 2007 4:30 am

den9 wrote:

i still dont understand how a 50mm prime lens is a 75mm on a dslr, is it because it has a larger sensor so its getting cropped?

this has been ask many times and don't get confused
50mm is 50mm in Focal length (they only say it equivalent to 75mm because of cropping the images to fit a smaller size sensor)

why is it that they said it will become 75mm in DSLR
because of the crop factor of 1.5x (now I'm getting redundant here LOL)

it will look likes 75mm in DSLR because of the CROP factor that the Sensor of DSLR is 1.5 compare to 1 of the film size

the focal lenght never change just the crop and field of view

here is another one
let say the film size is 1 inch in diameter the DSLR sensor is 0.75 of an inch to match the size of the film of 1 inch you need to blow up the 0.75 sensor so it looks like you zoom out from 0.75 to 1 to macth the film size thus making it looks like a 75mm to compare to film

so then again 50mm is 50mm in focal length it just change the field of view in DSLR

i hope this help

Joined: 14 Apr 2006 Posts: 224

to boil it down Den9 when a lens says it's equivalent in size its saying that picture you get from a 50mm lens on a digital body would be like putting a 75mm lens on a film body.

The lens focal length doesn't ever change, but the equivalency is from sensor to film.

so an 80-200mm lens is an 80-200mm lens no matter the medium, but because your sensor is smaller than film it is like taking the equivalent of a 120-300mm lens and shooting it on film.

in essence you take a picture with the same lens on a film and digital camera the printed picture will be magnified 1.5 times on digital than on film.

Posted: Sun Apr 15, 2007 7:00 pm

http://www.luminous-landscape.com/tutorials/understanding-series/dslr-mag.shtml

http://www.withinlights.com/Labo/Articles/CropFactor/index_us.php

Hope these help.

Joined: 18 Nov 2006 Posts: 288

den9 wrote:

i still dont understand how a 50mm prime lens is a 75mm on a dslr, is it becuz it has a larger sensor so its getting cropped?

It isn't a 75mm lens. It has an equivalent angle of view to a 75mm lens because the image is cropped. It is cropped because the digital sensor is smaller than the 35mm sensor and only records the central part of what the lens captures. If you were to take a 35mm negative and crop it on an enlarger during printing, you would have the same effect. You would capture the central part of the image on the print and crop off the edges of the frame.

A 50mm lens is considered a normal lens on 35mm, a modest telephoto on an APS digital sensor and a wide angle on medium format. It is still a 50mm lens with all the characteristics of a 50mm lens. The coverage, however is different for each format.

Joined: 11 Oct 2005 Posts: 176 Location: philly

ok i came across this, still confused a little

if i got a 50mm lens on a dslr and a 50mm lens on a film slr, took the same exact picture with both of them from the same distance, would they look the same, or would one be zoomed closer

Joined: 27 Oct 2004 Posts: 451 Location: Gloucester, UK

den9 wrote:

ok i came across this, still confused a little

if i got a 50mm lens on a dslr and a 50mm lens on a film slr, took the same exact picture with both of them from the same distance, would they look the same, or would one be zoomed closer

The majority of digital SLR cameras have a sensor which is considerably smaller than a 35mm film frame. The new Canon EOS 400D for example has a sensor 22.2 x 14.8 mm. The effect of this is that the same lens used from the same position will produce a cropped image on the DSLR. The image will be of the centre section of a 36x24 frame.
It is not 'zoomed closer' which would imply that the focal length of the lens has changed - it has not. Where the confusion comes in is with magazines repeating the same, incorrect information.
If you print a 36x24 image on 6"x4" paper and print a 22.2 x 14.8 image on the same size paper the smaller image is enlarged more. That is not the same as the camera actually capturing a more magnified image in the first place.