Re: Auto-focus on digital SLRs.

Wolfgang Weisselberg wrote:
> nospam <nospam@[EMAIL PROTECTED]
> wrote:
> 
>>Anon <abuse@[EMAIL PROTECTED]
> wrote:
> 
> 
>>>Try getting a dslr to focus on a white card or a blank wall when
there's 
>>>nothing else in view...
> 
> 
>>kinda hard to manually focus on that.
> 
> 
> Ever heard of microprisms?
> As in "microprism ring"?
> Try Google on that term, or ask your local dealer, preferably one
> that has a proper "old" manual focus SLR on hand for demonstration ...
> 
> -Wolfgang

Also there is the likelyhood that unless your blank wall or white card 
has no surface texture (ie perfectly smooth) and/or is illuminated 
completely evenly (no shadows from any surface texture), there is 
probably more than enough contrast for a DSLR camera to AF on the 
surface and also it's enough for manual focus without the aid of a split 
prism and microprism ring on the viewfinder screen anyway.