[Leica] leica digital back-initial test results

[jonathan at openhealth.org (Jonathan Borden)]

Frank Filippone wrote:
>
>
>
> Thank you Henning.  It is hard to believe that Ektar25, Tech Pan, 
> Velvia, or
> Tmax100 would not be sufficient to test any lens.  OTOH, there may be 
> some
> issues that a B+W film could not capture and that Velvia might not be 
> color
> sufficient for.
>
> My gripe with the whole digital thing is to come to terms wih capture
> software does something with the images.  It is not glass on film, it 
> is
> glass on sensor modified by some software and put on a CRT.  I find 
> that a
> third or fourth generation image ( digital) can touch a first 
> generation
> slide or B+W negative.
>

You might consider post processing software the rough equivalent to 
darkroom chemistry. Folks have selected various developers etc. in 
order to "modify" the latent image on film ... on the other hand one 
cannot actually see the latent film image, consequently there is always 
some "post-processing" for every image taken, whether this be silver 
halide or silicon.

> Through limitations in the sensor design/technology, some lens
> defects that were unnoticeable on film are now obvious on digital. In
> those cases, FF digital can be 'better' than the lenses, but you have
> to remember that part of that equation is a lack in the sensor.
>
> In other ways, the 'bull puckey' description applies.
>
> Digital does not come close to testing the MTF of the better lenses.

This all has to do with "MTF" issues, that is one has to compose the 
MTF of the sensor (digital or film) onto the MTF of the lens (and onto 
the MTF of any post processing), in order to get the actual image.

Considering this, it is possible that given a particular sensor MTF, 
one might need to design a particular lens in order to get the best 
possible resolution, i.e. that conceivably lenses might need to be 
designed with particular sensors in mind.

Jonathan