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Re: [OM] Mea Culpa - & - Scanners

Subject: Re: [OM] Mea Culpa - & - Scanners
From: "C.H.Ling" <ch_photo@xxxxxxxxxxxxx>
Date: Mon, 6 Jan 2014 09:30:37 +0800
----- Original Message ----- 
From: "Ken Norton" <ken@xxxxxxxxxxx>
>
>> Williams spends many pages describing the maximum resolutions attainable
>> by amateur and professional photographers using unskilled and skilled
>> hand held methods and low to high resolution films on up to heavy studio
>> grade equipment with very high resolution B&W and extreme measures take
>> to prevent vibration.  The average hand held photograph taken with
>> typical color films of the day fares poorly with resolutions ranging
>> from 20 lppm for the typical rank amateur to 30 lppm for the careful
>> amateur to 40 lppm for the very careful and meticulous processional.
>> It's actually rather disappointing since 40 lppm only translates to
>> (80x24) = 1920 pixels vertically and (80x36) = 2880 pixels horizontally
>> or about 5.5 megapixels for a 35mm film scan.  Is this perhaps where the
>> 5 MP resolution of the E-1 comes from as "good enough"?  Of course, it
>> probably takes 4000 dpi to actually resolve that 1920 pixels vertically.
>
> And this is where the rub comes in. It's not how many line pairs per
> mm there are in film, but where those line pairs are. What if those
> lines aren't exactly parallel or perpendicular to the sampling
> (scanning) technology? It takes much more scanner resolution to
> effectively oversample the film in order to get an adequate
> representation of what the film actually captured. I find that 4000
> dpi is pretty close to that, but 5400 (Minolta) would be even better.
>

I'm with you Ken, I think more than 4000dpi is required for the better 
slides/negatives if you want to accurately reproduce the details, lower 
resolution scan will distort the fine details (thin lines become thick...)

>
>> Resolution of low contrast areas in typical
>> color films only ranges from about 50 to 80 lines/mm and perhaps double
>> that in high contrast areas.  No matter how good and stable the lens the
>> end result can't be better than that and will likely be appreciably less.
>
> This is highly dependent on the film. Fujichrome Provia 100F being
> actually pretty bad in this regard. Velvia 100 (not F) is about the
> best Fujichrome.
>

I did some tests with the original Velvia 50, with the Zuiko 50/3.5 I got 
70lp/mm resolution.

I also found the old lenses/films with casual shooting not necessary mean 
low resolution, it depends on the type of image. Landscape under good 
daylight are usually having very high resolution. I have some 1980's Kodak 
Gold 100 with a Sigma zoom produce results that challenge my 5D II/80F4 copy 
setup. I also found copying with a DC is not pixel to pixel equal to a film 
scanner, I think it require double the pixel count for a closer match.

To get a high resolution landscape, the most challenging thing is shutter 
speed, to me the 1/focal length rule does not work, It require more than 
1/250s even with a standard lens. I once shoot with the Zuiko 50/1.4 on the 
5D II at 1/50s, I need to shoot five to get one really sharp image. Ok, the 
shutter shock of the 5D II is one thing to blame.

C.H.Ling











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