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Category: New Questions

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Photography Question 
Amit S. Gujrathi

member since: 6/14/2004
 

Film SLR Lenses Vs. Digital SLR Lenses


Are film SLR lenses compatible with digital SLR's? If yes, how can you tell which ones??

6/14/2004 2:48:11 PM

 
doug Nelson
DougNelsonPhoto.com

member since: 6/14/2001
  Some Nikon and Pentax digital SLR's can use the company's older manual-focus lenses, as well as autofocus lenses. Canon digital SLR's use EOS lenses. Any lens can be used that fits the camera, but there is a digital factor of about 1.4 that must be considered. For example, a 50mm Canon, Nikon or Pentax lens will be about a 70mm when used on a digital camera.

Nikon, Canon, Olympus, Tamron and probably others make lenses especially for digital SLR's. If you haven't yet decided on a digital SLR, consider a make that has its own digital-specific lenses.

6/15/2004 5:48:58 AM

 
Chris 

member since: 1/22/2004
  [quote] "Any lens can be used that fits the camera, but there is a digital factor of about 1.4 that must be considered. For example, a 50mm Canon, Nikon or Pentax lens will be about a 70mm when used on a digital camera." [unquote]

This is not correct. A 50mm lens on a digital SLR camera will still be a 50mm lens. The size of the objects will be identical to the size they would be if it were a normal full-frame 35mm film camera.

The difference is in the Field-of-View (FOV) ONLY. The FOV with a 50mm lens on a digital SLR will be as if it were shot through an 80mm lens.

So the objects within the image will be the correct size, but the amount of objects in the frame will be as if someone cropped the edges of the photo away. The factor is typically 1.6 for all but professional end digital SLR's and is known as the "crop factor".

It arises because the digital sensor in the SLR is about x0.6 the size of a 35mm frame. Thus a 35mm frame size is effectively divided by 1.6 (the crop factor) to get the digital SLR frame size.

Many people mistakenly believe that using their lenses on a digital SLR will effectively increase the focal length of that lens and "bring objects closer" than normal with that lens. It just isn't so. Only the FOV changes.

Chris UK

6/15/2004 3:36:51 PM

 
Andrew Hart

member since: 3/12/2004
  Be sure that you check the FOV multiplier before purchasing. This is variable across different manufacturers.
The EOS1D M2 is 1.3, Nikon D70 is 1.5, Sigma SD10 is 1.7 (same for SD9), Nikon D2H is 1.5, Canon EOS-300D is 1.6, Olympus E-1 is 2x (sourced from specs listed at www.dpreview.com).
This will mean that some will have better access to the wide end of the lens range than others.

Check before you buy!

6/16/2004 12:45:03 AM

 
Amit S. Gujrathi

member since: 6/14/2004
  Thank you very much guys !!
Amit

6/16/2004 6:29:13 AM

 
goutam sen

member since: 5/31/2004
  It seems very funny about the answer of chris because FOV or angle of view depends on the diagonal of the format,& as digital format is smaller so it's diagonal is as a reasult the angle of view is smaller & conversly a normal lens of a 35 camera shall act as a perfect tele photo to a digital format as it happens with 35mm & 120 mm,and I am confident about it because I use MAMIA 6/7,MAMIA 6/4.5,LINHOFF TECHNIKA,CANON 300D,& NIKON FM2N.REGULARLY.
GOUTAM SEN

6/16/2004 12:14:40 PM

 
Chris 

member since: 1/22/2004
  Gotam

The only thing that changes is FOV.

Take a 50mm lens and put it on a 35mm camera and point it at an object (a tree for example). Now without changing position, put the same 50mm lens on your Canon 300D. The tree will be EXACTLY the same size.

However, because the angle of view of the digital sensor is narrower (because it's only 22mm x 15mm rather than the 36mm x 24mm of a 35mm camera) it will not "see" as much of the scene as a 35mm camera film frame does.

So the scene is "cropped" by a factor of 36/24 if you take the horizontal dimension of the sensor or 24/15 if you take the vertical dimension or 43/27 if you take the diagonal dimension. It makes no difference to the result though... all of these come to 1.6, so the FOV of the 300D lens ids reduced by a factor of 1/1.6 = 0.6 BUT the focal length DOES NOT CHANGE.

Of course you can enlarge the photo to be as big as you like, but the tree on the sensor is definitely the same size as the tree on the 35mm film.

This has been repeated ad nauseum on many photo forums (or is it fora?)

Chris

6/16/2004 1:04:12 PM

 
Dave Cross

member since: 4/8/2004
  People.

To respond to Chris. I agree with you 100%, the image of our tree on the sensor will not change size.

BUT

Isn't the whole point that when you put the 50mm lens on the digital it APPEARS to be increased in length, and, to all intents and purposes IS the increased length.

BTW since one translation of 'forum' is "one place" or "central place" it can't have a plural -- or can it LOL.

Cheers
DC

6/17/2004 6:46:15 AM

 
Chris 

member since: 1/22/2004
  Dave
[quote]"...when you put the 50mm lens on the digital it APPEARS to be increased in length, and, to all intents and purposes IS the increased length......" [unquote]


Apologies Dave but I don't agree at all.

My point is that it DOESN'T appear to be increased in focal length.

Suppose you took a photo with a 35mm camera of say 20 people standing next to one another from left to right across the scene.

With the same lens and from the same position with a digital SLR the people would look exactly the same size but there would only be about 12 of them in the frame (ie: 0.6 x 20).

Nothing else changes.. only how much stuff is in the frame. There is no sense of there being some telephoto effect... just less people!

Chris

6/17/2004 7:21:03 AM

 
Dave Cross

member since: 4/8/2004
  Chris.
You are still right of course, and you don't need to appologise for that.

I think the reason people become confused over this issue is that the first thing they do with their photo (35mm or digital) is print it 6x4.

Now our cropped digital will need to be enlarged to a greater degree to fill the 6x4 paper, so our 12 people will be bigger on the print. Hence the APPEARANCE of a telephoto effect. Just as if we cropped out the centre of the 35mm and then blew it up to fill 6x4.

In this case we are BOTH right... it's just different points of view :-)

DC

6/17/2004 7:32:27 AM

 
goutam sen

member since: 5/31/2004
  Chris does not the magnification changes when I use a 50 mm lens in 300d and the same with a nikon film camera.If you calculate magnification you shall see that it increases by 1.5 times in a digital camera and more over the perspective acchieved in a digital camera with a lens of 35mm camera (in this case a little longer focal length shall shows better )is areal perspective instead of normal perspective.Does all these does not suggest that a 35mm camera lens serves a tele photo purpose in digital format ?

6/17/2004 11:44:08 AM

 
Chris 

member since: 1/22/2004
  Dave

You're quite correct in that (post-shot) we would enlarge the scene to fill the 6x4 and so there would indeed be an increased (digital) magnification of x1.6.

Goutam

[quote]"Chris does not the magnification changes when I use a 50 mm lens in 300d and the same with a nikon film camera" [unquote]

NO.... it doesn't. The optical magnification is exactly the same in both cases. A 50mm lens is still a 50mm lens in both cases.

As Dave quite rightly points out above we may choose to enlarge the print more to fill the say 6x4 photograph but this is digital magnification, after the shot is taken, NOT optical magnification which is to what you are alluding.

Chris

6/17/2004 4:45:23 PM

 

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