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Old Feb 24, 2009, 9:04 PM   #1
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I've got a D40 with 18-55 and 55-200VR. I often wonder what focal length represents "reality" as in no magnification. Exactly as the eye sees it.


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Old Feb 24, 2009, 9:34 PM   #2
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With 35mm, it was commonly accepted that "normal" focal length was somewhere around 50mm, give or take a few mm. On a "crop" camera, like a D40, this should be somewhere between 30mm and 35mm, with 33mm giving you the field of view of a 49.5mm lens on a full frame camera. Just my opinion, but I never found this information to be very relevant to anything I did with a camera. Hope I gave you a suitable answer, someone else may get more technical, but that's just about the gist of it.

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Old Feb 25, 2009, 5:26 PM   #3
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There isn't one ...

... at least not until you specify the camera format, such as "DX" for your D40, the print size, and the viewing distance (eye-to-print).

A "normal" lens has long be defined as one having a focal length equal to the diagonal measure of the film/sensor image, approximately 26-28mm for your D40 and 35-42 for 35mm film, depending on the cropping involved in printing. This definition as "normal" is based on the (unfounded) assumption that the final print will be uncropped and viewed at an eye-to-print distance equal to the diagonal measure of the print. If this viewing distance is used then a lens of "normal" focal length will deliver the perspective (forground vs background relationship) of the human eye/brain combo. Field of view will, of course, be different.
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Old Feb 25, 2009, 5:54 PM   #4
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I'm not asking about printing. I'm wondering what it would be as you look through the viewfinder.
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Old Feb 25, 2009, 10:16 PM   #5
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mckeand13 wrote:
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I'm not asking about printing. I'm wondering what it would be as you look through the viewfinder.
If you are just looking through the viewfinder and not taking pictures, you find that the visual image in the VF of most of today's DSLRs will give a "life size" (1x) image when the objective lens is somewhere between 50mm and 60mm. It will vary from model to model.

The standard for rating the VF magnification of a 35mm film or a digital SLR (any format between 4/3rds and 24x36mm) is to quote the magnification with a 50mm lens attached, though some manufactures may be using 52mm as that is the actual focal length of their "50mm" prime lenses. If you divide 50 by the rated magnification (e.g. 0.92x or whatever) the result will be the focal length that will yield a 1x VF magnification (~54mm if rated at 0.92x and the manufacture is really using 50mm as the reference lens, ~57mm if they're using 52mm).

Again, this is the VF image and not the resulting photograph, which gives varying impressions depending on its display size (either print or computer monitor) and the distance from which it is viewed.
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Old Feb 26, 2009, 1:59 PM   #6
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If you look at an object through the camera and open the other eye, you can move one image over the other and compare what your eye sees compared to the view through the camera with the other eye. I use a tree trunk about 50' away and tip the camera sideways. I've always thought my old Nikon film 50mm lenses were "normal" andmatched natural eyesight, but I tried one last week and it isquite a bit different, but I can't remember whether bigger or smaller.



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Old Feb 27, 2009, 11:20 AM   #7
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Why not find your own reality?

Shoot a few landscapes, looking at them with your own eyes, then zoom your normal/mainlens until the angle of view looks like you want it to look,check the zoom, make a note of that settingand presto, you've just set your own reality, which may be different from what we think. There are very few absolutes in this hobby. Don't try to box yourself intoone that isself-made.

It's all reality to me.
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Old Mar 9, 2009, 7:42 PM   #8
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I was told by a nikon rep that itis about 55mm's . So the max focal on 18-55 lens should be about it.
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Old Mar 10, 2009, 9:43 PM   #9
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mckeand13 wrote:
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I'm not asking about printing. I'm wondering what it would be as you look through the viewfinder.
I've run across this question several times and have heard many different opinions.

With your camera turned vertically, look through the viewfinder with your right eye while keeping your left eye open, and adjust a zoom lens until the superimposed images match. Check the focal length on the lens.

I have done this with 35mm film SLR, mid-zoom digicam, and DSLR. For me, it works out to the 35mm equivalent of about 75mm FL. YMMV

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Old Apr 10, 2009, 12:41 PM   #10
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I always believed a 35mm lens was closer to reality on a film SLR. IMO anyone with 50mm eyes has tunnel vision. 35mm on a film body would be 24mm on a Nikon DX DSLR.
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