"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

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.

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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...

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.

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
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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.

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

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

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.

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