digital optics

Ok, we know angle of view is linked to the focal length,

We know theres a 1.5 loss in angle of view on a digital camera.

How is that really effecting it optically?

 

my question is:

 

My 28mm lens has less angle of view, but is the optical lens

distortion still simaler to when i use that lens on my film SLR?

 

 

Does a 75mm or 100mm with a gain in angle of view still add to the

dynamic of portrait photography?

 

thanks

What lens distortion does your 28mm exhibit? They are all pretty well corrected by now, in 2005. Just wondering ...

 

Yes a 100mm (on film) lens now becomes 150mm and seems to shorten the perspective to the naive mind a bit more. But if you take the same framed shot from the same position with film and a DSLR, the digital image will just be a crop of the film image. And the perspective is quite the same. Perspective refers to size ratio of a close and a distant object here, as is usual.

 

So, yes, your 100mm lens will crop closer, giving the same perspective, however, from the same spot with a DSLR as it did for film. Go figure and try to understand the inate geometry. It is a bit difficult ...

From everything I have read, most optical problems occur toward the edges of a lens's image. With the digital crop effect much of the edge of the image circle (in a standard as opposed to DX lens) is removed, i.e. you're getting the heart of the lens's performance on the DX sensor. A DX lens has a smaller image circle to begin with so I'd expect more optical issues, such as the barrel distortion seen with the kit lens on the D-70 at its wide end.

Its like Pentax 6x7 lenses being used on smaller format cameras made by Pentax like the 645 or 35mm. The lens won't focus any closer or gain any speed but since the center of the lens is being used and the glass at the circumference is not the image will be sharper since the lense is operating in its sweet spot. The thing that is bad about all this mismatching lens to format is that a 28mm lens has always had a purpose for its design as a wide angle and as a 42mm normal lens on an APS small sensor digital camera it loses its reason for being.

 

Nikon and for that matter has substituted a series of zooms for purposeful prime lenses. The photographer has suffered in many technical ways, and so far no camera company has invested in new prime lens focal lengths to substitute for the old lenses like the fast 28mm; 35mm; 85mm and 105mm. A fast f/1.4 60mm DX format lens could for example be like a 90mm length portrait lens. It would be compact, have shallow depth of field, speed the zooms lack and have sharpness since the lens is optimized for one focal length. I miss the Idea of prime lenses being desireable as part of a system. In the old days a 24/35 /50/90/135 and a doubler was all you needed and they could all be F/2 or so and sharp. Zooms are wonderful but primes are needed to solve specific problems that both digital and film users run into.