Topic Author
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Joined: Sat Jun 23, 2001 3:25 pm

Digital SLR Viewfinders

Sun Jun 22, 2003 4:52 pm

I will shortly have a Nikon D100. I understand due to the size of the CCD a 1.5X factor is added to the lens. So when looking through the viewfinder do you see what the lens is actually seeing, or is the viewfinder magnified or cropped to allow for the 1.5X magnification?

I know that the latest Contax N and Canon 1DS have full (35mm) frame CCD/CMOS so there is no magnification issue with these models.


Topic Author
Posts: 114
Joined: Sat Jun 23, 2001 3:25 pm

RE: Digital SLR Viewfinders

Sun Jun 22, 2003 5:02 pm

I am assuming that you cannot preview a shot in realtime with the LCD on this model.

Just found this info on the web relating to the D100:
Viewfinder frame coverage Approx 95%
Viewfinder magnification Approx. 0.8x with 50mm lens set to infinity and -1.0 m-1

Can someone explain this?

Thanks again,


RE: Digital SLR Viewfinders

Sun Jun 22, 2003 5:28 pm

Check for information about all digital cameras.

Anders Nilsson
Posts: 1921
Joined: Mon Jan 28, 2002 10:48 pm

RE: Digital SLR Viewfinders

Sun Jun 22, 2003 6:01 pm

On the D100 and all other digital SLRs, WYSIWYG is in place. When you look through the viewfinder, you effectively have the 1.5x magnification in place. IE, you use 200mm (on your lens) to photograph the image. You are actually looking at it as through you are using 300mm (1.5x 200=300mm)for it.

D100 gives as stated 95% framing, which means that what you see on the viewfinder is 95% of the entire image. I think the higher end models give u up to 99% framing.

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Topic Author
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RE: Digital SLR Viewfinders

Sun Jun 22, 2003 6:51 pm

OK, so the viewfinder must have it's own 1.5X magnification lens or the mirror is the same size as the CCD to compensate, otherwise a standard size mirror will reflect the standard lens image to the viewfinder and not show what the CCD is seeing.

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RE: Digital SLR Viewfinders

Sun Jun 22, 2003 7:45 pm


Hope this helps, it is based on a Canon DSLR but the basics are the same

Ben Pritchard
Posts: 4586
Joined: Fri Aug 27, 2010 12:26 am

RE: Digital SLR Viewfinders

Sun Jun 22, 2003 8:15 pm

is the same size as the CCD to compensate

Yes, this is the case - the camera body is designed around the sensor and has been "scaled" to provide the same optical pathways as a normal SLR - much in the same way that APS or 110 SLRs were scaled.


Colin K. Work, Pixstel
Topic Author
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RE: Digital SLR Viewfinders

Sun Jun 22, 2003 9:07 pm

Thanks folks, it's all clear now.

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Joined: Fri Jun 13, 2003 9:11 am

RE: Digital SLR Viewfinders

Sun Jun 22, 2003 11:44 pm

There isn't any magnification in the viewfinder. The DSLR's (with smaller than 35mm sensors) have cropped viewfinders. You will notice a difference if you look in the viewfinder of a standard film SLR to a cropped DSLR (I say cropped, because 35mm sized sensors are found in DSLR's such as the Canon 1Ds - this doesn't have a cropped view finder).

Why the cropped viewfinder?
The image itself is cropped due to the small sensor, so the viewfinder should be cropped accordingly.

Why the cropped sensor?
I assume manufacturing costs of larger sensors (the price of the Canon 1Ds is prohibitive).

What does that mean for the image?
35mm SLR's are designed to have light projected onto the size of a 35mm film. The lenses are designed for the ground up to project to an area this size. By attaching the same lens to a DSLR, the same light is projected back onto where the film would normally sit. The DSLR sensor is smaller and hence surrounding light is lost that would normally be captured by film. This leads to cropping compared to film.
A 300mm shot taken on my Canon 10D gets cropped by 1.6x = 300 x 1.6 = 480mm. The perspective is exactly the same as seen by a 300mm lens so isn't the same as attaching a 500mm zoom lens.

This can best be explained by attaching a fish-eye lens to a DSLR.
Attach a fish-eye lens to a film camera and the barrel like distortion is noticiable as a border around the corners. With a DSLR, attaching a 17mm lens that would cause distorsion on film has a similar Field of View as a 28mm lens, but with a draw back - it maintains the distorsions of the 17mm - albeit excluding the corners - the worst part.

Glenn Stewart
Sydney, Australia
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