tomb@tekecs.UUCP (Tom Beach) (10/14/85)
> As an aside, does anyone out there know how to get good sharp > prints from 35MM slides? I've not had trouble getting sharp prints from sharp slides but I had always considered prints from slides to be inferior to prints from negatives *UNTIL* I discovered internegatives. Reversal color print processes are not as good as negative print processes. MY OPINION: Don't bother to flame if you disagree! Good color labs will make an intermediate negative, typically 120 roll film size, but I've had pro labs that used 4x5 sheet film. The subsequent prints are made from this negative. Clearly this costs more and isn't worth the cost for small prints but I would STRONGLY recommend this for enlargements of 11X14 and up, even 8X10 if it's special to you. I think you'll be pleased. -- Tom Beach email: ..tektronix!tekecs!tomb "The past is another country; they do things differently there."
sasaki@harvard.ARPA (Marty Sasaki) (10/16/85)
As a followup about inter-negatives. Kodak makes a very good interneg
film. It is sharp with good, accurate, color rendition. The only
problem is that it has a useful lifetime measured in days. Kodak
figures that once you have made the print, then you don't need the
internegative any more.
Marty Sasaki
--
----------------
Marty Sasaki net: sasaki@harvard.{arpa,uucp}
Havard University Science Center phone: 617-495-1270
One Oxford Street
Cambridge, MA 02138ron@brl-sem.ARPA (Ron Natalie <ron>) (10/16/85)
> Good color labs will make an intermediate negative, typically > 120 roll film size, but I've had pro labs that used 4x5 sheet > film. The subsequent prints are made from this negative. If you ask! Everybodies default seems to be TYPE-R prints, even from the best labs, but the good labs don't look at you funny when you say inter- negative and try to convince you that negatives aren't required. -Ron
hofbauer@utcsri.UUCP (John Hofbauer) (10/17/85)
> I had always considered prints from slides to be inferior to > prints from negatives *UNTIL* I discovered internegatives. No disagreement here. In fact, I feel internegatives from Kodachrome slides to be superior to a Kodacolour negative of the same size. > Reversal color print processes are not as good as negative print > processes. MY OPINION: Don't bother to flame if you disagree! Ever hear of Cibachrome? The results are luminous. Furthermore the dye stability is such that it won't fade when hung in a brightly lit room. It is ONLY a positive-to-positive process, and VERY expensive. Sigh!
briand@tekig4.UUCP (Brian Diehm) (10/21/85)
>> Reversal color print processes are not as good as negative print >> processes. MY OPINION: Don't bother to flame if you disagree! > >Ever hear of Cibachrome? The results are luminous. Furthermore the >dye stability is such that it won't fade when hung in a brightly >lit room. It is ONLY a positive-to-positive process, and VERY >expensive. Sigh! Sorry, Cibachrome DOES NOT provide the order of results you are looking for UNLESS you shoot the original slide with a Ciba print in mind. This is because the color saturation and contrast increase inherent in the print process CANNOT be controlled to match print to slide. However, if you overexpose the slide, you wind up with a washed-out slide that makes a pretty good Ciba print. It's a no good slide for anything else, though. Yes, Ciba is permanent - at least it's the most permanent color photographic process, in theory. The problem with making prints from slides is that by their nature slides can contain more information than a print can. If you compare the range of trans- mission densities possible through a slide with the reflection density range possible from any print, the print loses. The density range on paper, no matter what the process, is limited to around 2 f-stops, and that's with ideal illumin- ation and display, while the slide is theoretically unlimited. Since the density range of "reality" is quite wide (making metering a process of judgement), a slide can better match reality. The limits to the process are fundamental. However, that DOES NOT say that Ciba is even close to this ideal. On paper, the very best color reproduction is graphics arts 4-color separations, ink on paper. Ironically, this process operates best from transparencies! The best photographic color reproduction is from negatives, again if the objective is on paper. However, if you can get away from paper, transparencies can blow any- thing else away. Hence, the frustration of trying to put a slide on paper. At best, it will always be a compromise. -Brian Diehm Tektronix, Inc.
johnw@astroatc.UUCP (10/23/85)
In article <431@harvard.ARPA> sasaki@harvard.UUCP (Marty sasaki) writes: >... Kodak makes a very good interneg film. ... The only >problem is that it has a useful lifetime measured in days. Kodak >figures that once you have made the print, then you don't need the >internegative any more. > They figure if you later decide you want more prints, them you'll have to get another inter-negative!!! (There in the for the $$$) John W -- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - {...siesmo,allegra,ihnp4...} !uwvax!astroatc!johnw To err is human, to really foul up world news requires the net!
ems@amdahl.UUCP (ems) (10/23/85)
> >> Reversal color print processes are not as good as negative print > >> processes. ... > > > >Ever hear of Cibachrome? The results are luminous. ... > > Sorry, Cibachrome DOES NOT provide the order of results you are looking for > UNLESS you shoot the original slide with a Ciba print in mind. This is because > the color saturation and contrast increase inherent in the print process > CANNOT be controlled to match print to slide. However, if you overexpose the > slide, you wind up with a washed-out slide that makes a pretty good Ciba > print. It's a no good slide for anything else, though. ... > > The problem with making prints from slides is that by their nature slides can > contain more information than a print can. If you compare the range of trans- > mission densities possible through a slide with the reflection density range > possible from any print, the print loses. The density range on paper, no matter > what the process, is limited to around 2 f-stops, and that's with ideal illumin- > ation and display, while the slide is theoretically unlimited. Since the > density range of "reality" is quite wide (making metering a process of > judgement), a slide can better match reality. The limits to the process are > fundamental. > Something which has always bothered me, when you copy a print onto a slide (an perhaps other copies as well) you get 'contrast buildup'. It seems to me that if the contrast range of the print is *less* than that of the original subject, then the contrast range of the slide should also be *less* than the original. So why does the slide show *higher* contrast? I'm sure there is some simple inversion of logic that I am doing somewhere. Some trivial point I have missed... But miss it I have. I hereby cast my reputation for clear thinking onto the net to be ripped to shreds .... (Isn't it amazing what one will suffer to get an answer to an anoying problem?) -- E. Michael Smith ...!{hplabs,ihnp4,amd,nsc}!amdahl!ems 'If you can dream it, you can do it' Walt Disney This is the obligatory disclaimer of everything. (Including but not limited to: typos, spelling, diction, logic, and nuclear war)
dave@onfcanim.UUCP (Dave Martindale) (10/25/85)
In article <2141@amdahl.UUCP> ems@amdahl.UUCP (ems) writes: >Something which has always bothered me, when you copy a print onto >a slide (an perhaps other copies as well) you get 'contrast buildup'. >It seems to me that if the contrast range of the print is *less* >than that of the original subject, then the contrast range of the >slide should also be *less* than the original. So why does the >slide show *higher* contrast? There are two things to consider here - the contrast range that can be *represented* by a particular medium, and the contrast ratios of "good- looking" images in that medium compared with the contrast ratios of the original. A good print material is only capable of about a 30:1 range of reflectances. Thus, when printing, you set your exposure so that some area of the print comes out white, and anything in the image that is darker than 1/30 of this is mostly lost in the shadows. Transparency material, on the other hand, is capable of 100:1 contrast range or more. But representable contrast range has nothing to do with contrast buildup. For a particular photographic material, if you plot the log of reflectance (or transmittance) against the log of the illumination level, you will get an S-shaped curve with a centre section that is roughly straight. The slope of this curve is called "gamma". If it is 1.0, then a given change of luminance between two parts of the image will produce the same change in the photograph - there is no change in contrast (provided both luminances fall in the linear part of the curve, of course). If the gamma is 2.0, for example, then a 2:1 luminance change in the scene will produce a 4:1 change in the final image. Why would you want a gamma of other than 1? Well, it seems that a gamma of 1 is about right for prints, that will be looked at by reflected light. But for images that are projected (slides, movies) or self-luminous (TV), they appear subjectively "flat" or low in contrast if they have a gamma of 1, reproducing luminance ratios correctly. I believe that this has to do with darker tones appearing subjectively lighter than they are because the image is seen in a dark environment. Anyway, an overall gamma of about 1.5 seems to give these types of images enough additional contrast so that they look correct. So direct-positive films, television systems, and negative-positive movie film systems are all designed to produce a final gamma of about 1.5. And they work well if you photograph real images. But if you photograph a slide to duplicate it, you have now increased the total gamma to 2.25 (gammas multiply) and it looks too contrasty. To avoid this problem, you need to do duplication with a film that has a gamma somewhere down near 1.0. In real life, things are a bit more complicated than the description above, since the low-light end of the response curves of many films have a greater gamma than at higher light levels in order to compensate for the loss of contrast due to lens and camera (or enlarger or printer) flare. Dave Martindale
jer@peora.UUCP (J. Eric Roskos) (10/27/85)
> Reversal color print processes are not as good as negative print > processes. MY OPINION: Don't bother to flame if you disagree! Why would anybody flame you! :-) After all, it's true... Color rendition in prints from color negatives is better than the color rendition in prints from slides. This is because present-day dyes have "tails" on their spectral absorption curves that overlap the spectrally-absorptive regions of the other dyes. This is particularly a problem for the cyan layer, and to a lesser degree, the magenta layer. The result of this effect is a color "impurity" in the negative image, typically a red impurity in the cyan areas, and a yellow impurity in the magenta areas. To correct for this, color negative films have a yellow and a red color mask whose color is decomposed in proportion to the presence of the corresponding impurity. Thus in an area with a large yellow impurity, the yellow mask will be almost completely decomposed, i.e., the yellow mask goes away, to be replaced by the yellow impurity. Likewise for red. The result is that the film has a uniform yellow-red cast to it, rather than having a red cast in the cyan areas and a yellow cast in the magenta. However, with slide films, this can't be done, since the slide is intended to be viewed by projection, and a yellow+red cast (well, possibly the complementary colors for a reversal film) would be unacceptable, whereas when printing from a negative this can be corrected with color correction filters. Thus, so that the whites will be white on a slide, the other colors have to be compromised slightly in the print. This is why color negative films exist. (Well, also because the processes to develop them are simpler.) Contrary to popular opinion fostered by the fact that photojournalists and others who intend their photographs to be reproduced by ink printing use slides (and the biased editorial position of some popular photography magazines), the color rendition of color negative films is "truer" than for slide films. It should seem intuitively probable that a film that is *designed* for making prints would be better-optimized for making good prints than a film that was designed for making slides which are occasionally printed. On the other hand, grain is marginally better in Kodachrome. It's my personal feeling that image sharpness is not sufficiently good with 35mm cameras to make that much of a fuss over grain (eventhough I do use a very fine-grain B&W film myself!) when comparing an ASA 100 film with Kodachrome, and they don't make Kodachrome for larger-format cameras. -- Shyy-Anzr: J. Eric Roskos UUCP: Ofc: ..!{decvax,ucbvax,ihnp4}!vax135!petsd!peora!jer Home: ..!{decvax,ucbvax,ihnp4}!vax135!petsd!peora!jerpc!jer US Mail: MS 795; Perkin-Elmer SDC; 2486 Sand Lake Road, Orlando, FL 32809-7642
bhuber@sjuvax.UUCP (B. Huber) (10/29/85)
> Something which has always bothered me, when you copy a print onto > a slide (an perhaps other copies as well) you get 'contrast buildup'. > It seems to me that if the contrast range of the print is *less* > than that of the original subject, then the contrast range of the > slide should also be *less* than the original. So why does the > slide show *higher* contrast? > > E. Michael Smith ...!{hplabs,ihnp4,amd,nsc}!amdahl!ems > The contrast range of a medium basically is the difference between its blackest black and its whitest white. Actual scenes can have an apparent range of over 10 f-stops; the greatest range typically available on B&W paper is about 7 stops. The photographic process reproduces images, then, by "squashing" the grays: differences between grays are understated in the image. A contrasty image is one, then, which represents a fairly small range of grays with its full black-to-white spectrum; a noncontrasty image will reproduce a wide range with nearly uniform gray. To answer your question: The contrast range of the slide is (except in extremely exposed cases) constant for all subjects; what concerns you is the relation between a given contrast range in the subject and the range of brightnesses with which that is reproduced. Think of it like this: a demagogue will reproduce ideas as either black or white, with little gray in between. A sophist will never use either extreme; everything is just shades of gray. The demagogue's black isn't really blacker than the sophist's; nor is one's white really brighter than the other's. What differs is how they compress or expand the ideas in the middle. The former is contrasty, the latter far less so.
ron@brl-sem.ARPA (Ron Natalie <ron>) (10/31/85)
> The contrast range of a medium basically is the difference between its > blackest black and its whitest white. Actual scenes can have an apparent > range of over 10 f-stops; the greatest range typically available on B&W > paper is about 7 stops. I disagree with this simplistic view. The black and white intensities are not what determines contrast, but the number of distinguishable intensities. Take it as sort of a visual S/N ratio. Both grade 1 paper and Kodalith have the exact same white and black values, but you can see more shades of grey on the lower contrast paper. I'm don't think f-stops are a valid unit here. Actual scenes is a misnomer here as well. What you are really saying is the human eye has a much greater contrast range than any film does.