Archived posting to the Leica Users Group, 2004/02/16

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Subject: Re: digital lenses was: Re: [Leica] Digital Bessa RF
From: "animal" <s.jessurun95@chello.nl>
Date: Mon, 16 Feb 2004 23:53:17 +0100
References: <005101c3f4d4$f995bd10$6401a8c0@CCA4A5EF37E11E>

- ----- Original Message ----- 
From: "B. D. Colen" <bdcolen@earthlink.net>
To: <leica-users@mejac.palo-alto.ca.us>
Sent: Monday, February 16, 2004 10:36 PM
Subject: RE: digital lenses was: Re: [Leica] Digital Bessa RF


> Actually, someone has done such film to mgp approximations and come up
> with, among other things, the fact that at between 5-6 mgp you get
> results equal to that of 35 mm tri-x. Which is all I care about. ;-)
>
> -----Original Message-----
> From: owner-leica-users@mejac.palo-alto.ca.us
> [mailto:owner-leica-users@mejac.palo-alto.ca.us] On Behalf Of Jonathan
> Borden
> Sent: Monday, February 16, 2004 4:07 PM
> To: leica-users@mejac.palo-alto.ca.us
> Subject: digital lenses was: Re: [Leica] Digital Bessa RF
>
>
> Feli di Giorgio wrote:
>
> >On Mon, 2004-02-16 at 03:00, frank.dernie@btinternet.com wrote:
> >
> >
> >>The problem is, Jim, that we do not need film dimension to match film
> >>quality,  digital sensors about 1/4 the size of Minox film match 35mm
> >>P&S quality. We  only need a full size sensor to utilise the full
> >>angle of view of our existing  35mm design lenses
> >>
> >>
> It is a mistake to assume that an optimal 35 mm lens (e.g. "M" series)
> will be optimal for a smaller imaging area. Consider state of the art LF
>
> lenses e.g. the Schneider Symmar XL 150mm f5.6 which covers 8x10" -- I
> don't see people clamoring to use this in 35mm -- indeed it would be a
> rather mediocre lens even though its sweet central spot covers > the
> 35mm film area.
>
> The issue is that optimizing a lens for 8x10 is much different than
> optimizing a lens for 35mm or a smaller area.
>
> >Frank
> >
> >That may be true, but I really detest the increase in DOF you get with
> >the 1.5 multiplication factor.
> >
> >
> >
> I believe the actual DOF is related to the F stop and focal length -- 
> you mean the *apparent* increase in DOF. The way to correct for that
> would be to use a wider F stop. Indeed for a lens optimized to a smaller
>
> imaging area you should be able to use a wider maximal F stop. All else
> being equal such a lens should also have a *high* resolving power in
> lpmm.
>
> The question has arisen as to how many pixels are needed to approximate
> 35mm film. Assume 75 lpmm that would be approximately 2000 lines x
> 2000lines or at least 2 pixels/line = 16 megapixels. Now if your lens is
>
> not good, or your focus is off or your hands shake etc, you need less
> pixels -- and also remember that there isn't necessarily a 1:2
> correlation between lines and pixels (for example it is widely
> acknowledged that a digital CD recording at 44 khz cannot truly
> reproduce an analog recording even though the human ear cannot hear > 20
>
> khz) i.e. you probably should have more pixels to capture all the
> information.
>
> In any case this is a back of the napkin approximation that tells us
> that a good 5 megapixel sensor is not enough to equal good 35mm film
> given a high quality lens. The 75 LPmm is for Provia F 100 slide film --
>
> for Tech Pan and on a tripod, you are going to need many more
> megapixels.
>
> Jonathan
> --
Even when handholding at 1/60 the resolution is higher then 5 megapixels
just tried this with a friend with a stabilised Canon.This is a crop from a
slide exposed 3 stops under by mistake at 1/60 th on 100 iso film
http://www.leica-gallery.net/apekop/image-60653.html
this is from the Canon with IS on
http://www.leica-gallery.net/apekop/image-60650.html
this is at 1/8th on film
http://www.leica-gallery.net/apekop/image-60652.html
it,s very funny if you blow up the tiff,s and see the artifacts of the
digital image.
looks great though with little noise.even shots from a tiny ixus 2.1mp
looked suprisingly good.
http://www.leica-gallery.net/apekop/image-60655.html
We have no doubt however that the 5mp camera would not improve much by
putting it on a concrete block while the film would.
The target was 50 feet away
http://www.leica-gallery.net/apekop/folder-6280.html
best regards
simon jessurun

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In reply to: Message from "B. D. Colen" <bdcolen@earthlink.net> (RE: digital lenses was: Re: [Leica] Digital Bessa RF)