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#1
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"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? -- Mark Photos, Ideas & Opinions http://www.marklauter.com |
#2
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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. 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. -- -- 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. |
#3
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"Alan Browne" wrote in message ... 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. 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... Or special lenses for black and white... |
#4
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Martin Francis wrote:
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 -- -- 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. |
#5
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In article ,
Alan Browne wrote: Martin Francis wrote: 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. 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. -- Email: | 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 --- |
#6
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DoN. Nichols wrote:
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. :-) 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. -- -- 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. |
#7
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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. -- Mark Photos, Ideas & Opinions http://www.marklauter.com |
#8
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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. 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. -- Paul Furman http://www.edgehill.net/1 san francisco native plants |
#9
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Paul Furman wrote:
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. 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. 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. -- -- 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. |
#10
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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. -- Mark Photos, Ideas & Opinions http://www.marklauter.com |
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