Re: [Leica] OT - film resolving power

[Christer Almqvist <chris@almqvist.net>]

Resolving power of the negative says very little  (IMHO: nothing) 
about how sharp/clear an enlargement looks. T-Max 100 is well known 
for producing less than sharp looking prints. The fine grain of this 
film may be an advantage, but to me the disadvantage for a Leica 
photographer of this film, i.e. the muddy look, is much greater than 
the advantage of having fine grain and high resolution.

Also, resolution figures say very little  (IMHO: nothing) unless the 
corresponding contrast index of the developed film is given. It is 
easier to get high resolution if the film is developed to a very high 
contrast than if it is developed to what most of us call normal 
contrast, but the image quality for pictorial work of prints from 
high contrast negatives is unacceptable in most cases.

The film with the highest resolution at normal contrast I have ever 
tested is the new Kodak Image Link film (see Kodak web site for 
meager details). It is available in 35mm double perforated rolls, 
unfortunately generally only in 30.5 meter length, and even worse, 
these rolls are only sold in 20-packs! I guess the well known POTA 
developers used for Tech Pan will all work with this film. For 
pictorial use there is no advantage in having this super high 
resolution which you buy at the cost of low film speed, not to speak 
of the extra dollars.

I have some comparable resolving power figures from my own test. Of 
course these are only comparable figures, not absolute ones.  For all 
tests I used a 35 mm Summicron at 5.6 at 40x focal length, enlarged 
16x with 40 mm Focotar at 5.6 and analyzed with a 10x loupe. Some of 
my figures are:

TMX in Perceptol 1+3 resolves 80 lines
Delta 100 in Xtol 1+1 sometimes resolves almost 100 and looks sharper 
than TMX above
Delta 100 in Rodinal 1+50 with 1 gram of Na asc resolves 80 but looks 
the sharpest of all.
Image link in Spur exceed the limits of my test chart which is 100. I 
guess it would be 125 or even 150 if I had a better test chart.

Now for the conclusion:

Go take pictures guys. Don't change a winning horse.
Limit the number of developers (Xtol and Rodinal for me). Limit the 
number of films (Delta 100 for me for normal films and one of the 
following for 400: HP5 or Delta 400 or Tri-X or TMY)

Use a tripod for high  resolution and sharpness

Chris

>Results of testing the resolving power of several films with actual
>photographic lenses (rather than by the film manufacturers' laboratory
>procedures) are reported in "Camera Lens News #19" at www.zeiss.de . Some
>examples are: T-Max 100: 180 line pairs per millimeter; Velvia: 160 lpmm;
>Portra 400 b/w and Portra 160 VC: 150 lpmm.
>Oliver Bryk
>
>
>--
>To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html


- -- 
Christer Almqvist
D 20255 Hamburg and / or
F 50590 Regnéville sur Mer

please look at my NEW  b+w pictures at:    http://www.almqvist.net/chris/dozen/

old pictures still at:     http://www.almqvist.net/chris/new
- --
To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html