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Photo Forum / Digital Photography / DSLR Cameras / May 2005"film" and "digital" lenses
Someone said in alt.photography that "film" lenses are designed to focus the different color wavelengths differently to make up for the layered emulsion in film. That sounds like non-sense to me. Opinions?  SignatureMark Photos, Ideas & Opinions http://www.marklauter.com > Someone said in alt.photography that "film" lenses are designed to > focus the different color wavelengths differently to make up > for the layered emulsion in film. That sounds like non-sense to me. I believe you're right. The 'layers' of film emulsions are so thin as to escape correction in the optics. Film thickness variance, optics variances, film transport variances and so on, combined, are huge compared to the thin-ness of the film emulsion. Further, the film companies have differing emulsion build up designs, including Fuji "4th layer" in some negative films. I never heard of needing special lenses for that... > Opinions? The only 'issue' I know of, and don't pay much attention to, is whether UV filters are necessary anymore. A flat piece of optical glass as a sacrificial filter (or better: none at all) is all that is needed. This does apply to CCD (lower UV sensitivity than film), I don't know about CMOS. OTOH I've seen another claim that lack of UV filtering may lead to 'blooming' when photosites are close to saturation. (May apply to CMOS and not CCD, I don't know). All the lenses, unless designed to filter specifically, pass a range of light far larger than the visible range we're interested in but are centered in the visual spectrum where focus on the film plane is concerned. The sensors have filtering (to greater or lesser degrees) in their covers to block IR and possibly UV. Cheers, Alan. Signature-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm -- [SI] gallery & rulz: http://www.pbase.com/shootin -- e-meil: Remove FreeLunch. > > Someone said in alt.photography that "film" lenses are designed to > > focus the different color wavelengths differently to make up [quoted text clipped - 10 lines] > including Fuji "4th layer" in some negative films. I never heard of > needing special lenses for that... Or special lenses for black and white... >>Further, the film companies have differing emulsion build up designs, >>including Fuji "4th layer" in some negative films. I never heard of >>needing special lenses for that... > > Or special lenses for black and white... Good point. Cheers, Alan Signature-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm -- [SI] gallery & rulz: http://www.pbase.com/shootin -- e-meil: Remove FreeLunch. >>>Further, the film companies have differing emulsion build up designs, >>>including Fuji "4th layer" in some negative films. I never heard of [quoted text clipped - 3 lines] > >Good point. I seem to remember a special three-layer B&W film from perhaps the late 1960s or early 1970s. I have never used it, but I read the reviews of it with great interest. Each layer was a different ISO, and by selective color filtration in the enlarger, you could select the layer which had what you wanted. IIRC, the review showed a shot of a clear glass light bulb, in operation, and from one layer, you could get the image of the glass envelope (with the filament vastly over-exposed), while from another, you could get an image which showed detail of the glowing filament. But, granted, this is an extreme example, and as far as I know, the film had a very short life in the market -- just too special purpose. :-) Enjoy, DoN. SignatureEmail: <dnichols@d-and-d.com> | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- > I seem to remember a special three-layer B&W film from perhaps > the late 1960s or early 1970s. I have never used it, but I read the [quoted text clipped - 12 lines] > the film had a very short life in the market -- just too special > purpose. :-) I love trivia like that. People tried to achieve new things in smart ways. Like you say, a little too special for a market that demands fast access to the film and reasonable turnaround. That film seems to have required too much post processing to be any fun to use. Cheers, Alan. Signature-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm -- [SI] gallery & rulz: http://www.pbase.com/shootin -- e-meil: Remove FreeLunch. >> I seem to remember a special three-layer B&W film from perhaps >> the late 1960s or early 1970s. I have never used it, but I read the [quoted text clipped - 20 lines] >Cheers, >Alan. Ilford XP1 = garbage. It had supressed grain but was so finicky when it came to contrast it wasn't worth using. -Rich > > Further, the film companies have differing emulsion build up designs, > > including Fuji "4th layer" in some negative films. I never heard of > > needing special lenses for that... > > Or special lenses for black and white... That was the first thing I considered. I even asked the poster about that and several folks have replied that he's full of $#@!, but he has apparently disappeared. SignatureMark Photos, Ideas & Opinions http://www.marklauter.com > Someone said in alt.photography that "film" lenses are designed to focus the > different color wavelengths differently to make up for the layered emulsion > in film. That sounds like non-sense to me. > > Opinions? I heard there is a coating on the rear element to prevent reflections off the sensor for digital lenses though I've not seen any example of these reflections so I assume it's quite a minor issue. SignaturePaul Furman http://www.edgehill.net/1 san francisco native plants >> Someone said in alt.photography that "film" lenses are designed to >> focus the [quoted text clipped - 7 lines] > off the sensor for digital lenses though I've not seen any example of > these reflections so I assume it's quite a minor issue. So minor that DSLR's cannot do OTF TTL metering. Any need for coatings to help in this regard sounds like the cry of the marketeers. Cheers, Alan. Signature-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm -- [SI] gallery & rulz: http://www.pbase.com/shootin -- e-meil: Remove FreeLunch. > I heard there is a coating on the rear element to prevent reflections > off the sensor for digital lenses though I've not seen any example of > these reflections so I assume it's quite a minor issue. Wouldn't film do the same thing? It's shiny plasticy stuff after all. SignatureMark Photos, Ideas & Opinions http://www.marklauter.com >> I heard there is a coating on the rear element to prevent reflections >> off the sensor for digital lenses though I've not seen any example of >> these reflections so I assume it's quite a minor issue. > > Wouldn't film do the same thing? It's shiny plasticy stuff after all. Not as shiny. BTW, you wouldn't necessarily see the reflections, they can manifest as a general lack of contrast. SignatureBen Rosengart (212) 741-4400 x215 Sometimes it only makes sense to focus our attention on those questions that are equal parts trivial and intriguing. --Josh Micah Marshall >> I heard there is a coating on the rear element to prevent reflections >> off the sensor for digital lenses though I've not seen any example of >> these reflections so I assume it's quite a minor issue. > > Wouldn't film do the same thing? It's shiny plasticy stuff after all. Not as shiny. BTW, you wouldn't necessarily see the reflections, they can manifest as a general lack of contrast. SignatureBen Rosengart (212) 741-4400 x215 Sometimes it only makes sense to focus our attention on those questions that are equal parts trivial and intriguing. --Josh Micah Marshall "Ben Rosengart" <br+rpdss@panix.com> wrote in message > BTW, you wouldn't necessarily see the reflections, they can manifest > as a general lack of contrast. I hadn't considered that. Thanks. SignatureMark Photos, Ideas & Opinions http://www.marklauter.com >> I heard there is a coating on the rear element to prevent reflections >> off the sensor for digital lenses though I've not seen any example of >> these reflections so I assume it's quite a minor issue. > >Wouldn't film do the same thing? It's shiny plasticy stuff after all. The film itself is (that is the plastic backing material), but the emulsion which faces the lens is typically a matte gray prior to development. Thus it is not capable of specular (mirror-like) reflections. There is also typically a darker coating on the back of the film to reduce reflections from particularly bright highlights which can punch through the emulsion and reach the back. This is dissolved in the processing of the film. Enjoy, DoN. SignatureEmail: <dnichols@d-and-d.com> | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- > Someone said in alt.photography that "film" lenses are designed to focus > the different color wavelengths differently to make up for the layered > emulsion in film. Thats BS.. SignatureStacey Mr. Mark wrote: > Someone said in alt.photography that "film" lenses are designed to focus > the different color wavelengths differently to make up for the layered > emulsion in film. Like George Preddy claiming Lateral Chromatic Aberration was a Sigma feature... > > Someone said in alt.photography that "film" lenses are designed to focus > > the different color wavelengths differently to make up for the layered > > emulsion in film. > > Thats BS.. Thanks all to answered. It sounded like a load of crap, but I'm no expert. :) SignatureMark Photos, Ideas & Opinions http://www.marklauter.com >From my personal evaluation of film lenses on digital ... ... it seems to be a generational thing. Some particular coatings that have a desired effect on film have a negative effect with digital. My Pentax SMC 30/2.8 is outstanding for both film and digital, as are the newer Pentax-F 50/1.7 and Pentax-FA 50/1.4. But the "A" series lenses (Pentax-A 50/1.7, 35/2, and 100/2.8 [non-macro]) are only average lenses. There's some color fringing toward the edges unless I correct the white balance. So the answer is yes and no. Some film lenses don't perform well with digital. But some do. It's not necessarily because they were film lenses. There is a correlation, but it is not a causal relationship. Conversely, digital lenses should always perform well with film, especially with traditional b&w with its single-layer emulsion. In the Pentax world, the new Pentax-DA 40/2.8 is a tempting new offering, well-suited for both fomats. (But I'm not quite ready to shell out $399 for it.) Yes, it's another pancake. And a pretty one at that. Collin KC8TKA > Conversely, digital lenses should always perform well with film, Well, watch out for "digital" lenses that project a smaller image circle. You'll get *severe* vignetting on a film camera. SignatureBen Rosengart (212) 741-4400 x215 Sometimes it only makes sense to focus our attention on those questions that are equal parts trivial and intriguing. --Josh Micah Marshall True. Some of Pentax' newer releases are for both (DA series, iirc) and others are only for digital. Collin |
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