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[OM] Re: advantage of higher res. scan when downsampling?

Subject: [OM] Re: advantage of higher res. scan when downsampling?
From: Siddiq <iddibhai@xxxxxxx>
Date: Mon, 21 Feb 2005 21:31:33 -0800
On Mon, 21 Feb 2005 17:29:58 -0800, Moose <olymoose@xxxxxxxxxxxxxxx> wrote:

> Siddiq wrote:
>
>> is there any technical reason to prefer higher resolution scans if the  
>> end
>> product is web-gallery use? 1800x1200 vs 3600x2400 roughly, say? the
<snip>

> "Another useful way of getting multiple image samples is to scan at a
> higher resolution and then average adjacent blocks of pixels. For
> instance, scanning at 2700 dpi and averaging every 2x2 block of pixels
> will result in a higher-quality 1350 dpi scan than just scanning at 1350
> dpi. Scanning at 1350 dpi in this case will throw away every other pixel
> and every other scan line, while scanning at 2700 dpi and setting
> "Output|TIFF size reduction" to 2 will result in averaging 2x2 blocks of
> pixels and increasing the number of effective bits of resolution by 2  
> bits."

aaaah, I see.

<snip>
>> both are JPEG format (i KNOW i read that fuji frontier can output to  
>> lossless TIFF format on photo.net threads, but i guess it depend on how  
>> well the operator knows the machine, in my case they said they can do  
>> high res, not lossless).
>>
> You may not be asking the right question here. JPEG compression can be  
> lossless, very slightly lossy, but nonetheless quite high quality, or  
> highly compressed and pretty bad. The JPEG process allows a wide range  
> of quality/compression settings. You need to know what quality the scan  
> outputs are and what that means in terms of results.

about 600mb for 4 roll of 36exp.

<snip>
> Another issue with the scans you are buying is that they are 8 bit.  
> That's fine for most shots, IF they get the histogram right. If not, and  
> for images with very wide dynamic range, they are not going to give you  
> what is in the film. Also, for images that need considerable adjustment  
> to brightness, color, contrast and/or curves, the 8 bit dynamic range  
> starts to get holes and bumps that can make the image look "funny" in  
> sometimes hard to describe ways. Scanners with 12, 14, 16 bit depths  
> don't have the same problem.

hmm, 8bit/ch yes. if you don't mind, i'd like to send you a few shots with  
tricky lighting, straight off the cd, so you cna see what the historgram  
look like. maybe i haven't seen any really good scanning, because the CD  
histogram looks fairly decent to me.

-- 
/S
aim:iddibhai
icq:104079359
email/msn:msidd004atstudentdotucrdotedu


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