Re: 1.5X Sensors VS. Full Frame and other questions...


"Mark²" <mjmorgan(lowest even number here)@cox..net> wrote:
Progressiveabsolution wrote:
What exactly does the 1.5X crop do to the image that is produced from
the camera? In other words, does it degrade the quality of the
picture when comparing to a full framed camera body?

What is the essential difference in image quality between a full frame
body and a 1.5-1.6X cropped body?

How much of a difference is there in image quality between the full
frame body and the 1.5-1.6X sensor bodies?

I'm sure this has been answered but hopefully I can get some more info
on this.

Thanks all for your help!

The lens still projects a full-frame image...its just that the sensor only
sees the middle portion of it due to the sensor's size being smaller than
the full-frame projection. Think of it as a slide projector projecting a
6 foot wide image onto a 5 foot wide screen. The projected image stays
the same...you're just not catching all of it on the screen.

Because of this, image quality is not changed at all...rather, you are
simply (in effect), utilizing all your sensor's pixels on the "sweet spot"
of your lens.

Ah, but you are enlarging the sweet spot 1.5x times more. So the question
becomes: is the center section of a 35mm lens really 1.5x times better than
the whole area of a 50mm lens.

Since the 35mm lens is designed to cover 24x36, it's a much wider angle lens
than the 24x36 50mm lens, and is going to have _worse_ performance, not 1.5x
better performance. Even comparing a point, say, 10mm off axis on the 35mm
lens with a point 15mm off axis on the 50mm lens.

Some see this as an advantage due to decreased vignetting and the use of
only the sharpest portion of the lens. Others who want wide angle may not
like losing the wide angle of view they are used to...

The decreased vignetting _wide open_ comes at the cost of reduced
resolution/contrast. It's really hard to make wide angle lenses, and for
lenses with an 80mm or wider FOV, cropped cameras with legacy lenses are a
bad idea.

The good news is that this effect doesn't apply to telephotos. But
telephotos (other than cheap consumer zooms) don't have a sweet spot,
leaving you with the 1.5x greater enlargement penalty. Oops.

The idea that a smaller sensor is better flies against 150 years of
photographic common sense, and is simply nuts.

David J. Littleboy
Tokyo, Japan


.

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