High Res Scans

[rob_garsson]

<p>First off I'm kind of a noob when it comes to scanning. I've read from a few sources that when scanning negs (medium or 4x5) past 2000 dpi the differences in quality become imperceptible. Would you say that's generally true, even for large prints (say 20x30 or larger)?</p>

<p>I'm sure the answer depends on many factors, such as how good the original neg is and what type of scanner is being used. For the purposes of this conversation I can't afford drum scans and will likely be working with an older imacon 848. While I plan to run some tests of my own in the next few weeks I thought I'd pose this question here as it may influence the next camera I buy. Say working from a 6x7 neg is it worth scanning at 3000 dpi instead of 2000 if I take advantage of the resolution when printing big? Does it simply add noise when scanning past a certain resolution? I find it kind of curious that the imacon 848 has different resolutions per film size, from 8000dpi at 35mm and 2040dpi at 4x5 (http://www.hasselblad.se/media/af870cd4-d074-4eff-b81c-2cfd18fb6cac-Flextight_848_English.pdf). Is there a reason it can't scan the 4x5 at 8000 dpi? Are the numbers for 35mm bloated?</p>

<p> </p>

[wolf_weber]

<p>For one thing Rob, an older Imacon 848 sounds like a good choice if the unit got serviced on a fairly regular basis<strong>..!</strong> If I remember correctly, the model has a diffuser incorporated which can greatly reduce the amount of time needed to prepare an image for printing, etc. When the scanner came to market <strong>FILE SIZE</strong> was still an issue, therefore a 6x7 or 5x5 scanned at anything higher than, say, 3000dpi would have produced files few PC's could have handled within reasonable delays. Also, if need be, especially today, there are many good ways to obtain increased file size without loss of resolution & detail.<br /> I the Imacon scaner wasn't so large and heavy (for transport back & forth to get serviced) I would trade my current Coolscan 4000, not because I am not content with results, but rather because scanning with the 848 is so much faster.</p>

[john_a5]

<p>I have an 848 and it is a great scanner. I scan most everything as 3F files at maximum resolution so that I have the option of multiple outputs from the same scan (3F's are sort of a RAW file).</p>

<p>You do get much better results from using larger files when making large prints--less resampling. But if you camera is not up to snuff, files will look better when scanned at lower resolutions. I had a camera I used for a few years, never scanning over 50-60mb files and everything looked good. When a client wanted very large files, I scanned them full resolution and the flaws in the lenses and camera became very clear.</p>

<p>The 848 is sort of like a scanner as it has an enlarger lens in it. If you consider you get a 2000 dpi scan from a 4 inch wide neg/chrome then using the same sensor, that would be an 8000 dpi scan from a 1 inch wide neg/chrome. The lens moves inside the scanner to accommodate the film size. I don't remember if it is 35mm or one of the other formats, but one of the formats will scan at a higher resolution if it is scanned vertically versus horizontally--probably 35mm.</p>

[john_a5]

<p>"The 848 is sort of like a scanner" well it is a scanner, I meant an enlarger!. </p>

[mattb1]

IMO, you can get more than 5000 dpI of info from film and it will indeed be noticeable. The question becomes if the

technique used for the photo was good enough to record that much info. 2000 dpi from MF or LF? IMO, that is not

why I would shoot a larger format.

 

The imacons were well regarded, I have never used one though. I'm sure their attention to quality would make their

lower res scans look better than the higher res scans. A lot more goes into a good scanner than a high pixel count.

Great glass and light source and image chip, not to mention how the film is handled. I would be concerned about

support, and repair.

[john_h.1]

<blockquote>

<p>dpi scan</p>

</blockquote>

<p>?</p>

[rob_garsson]

<p>Wolf: Right-o on the file sizes. 4x5 negs at 2040dpi and 16bit come back as 450mb files. Luckily my computer can handle them pretty decently.</p>

<p>John A: In regards to the scanner and resolution while I believe what you're saying is true it still doesn't make logical sense to me, in that if the scanner can get 8000 dpi from a 1" wide neg wouldn't it be 4x that (32000 dpi) for a neg that is 4" wide? I'm sure I'm missing something. Oh well, I'm not terribly astute on the technical end, maybe knowing that 2k is the best I can get from this scanner for 4x5's is all I need to know.</p>

<p>Matt: What type of scanner do you use?</p>

[robert lee]

<blockquote>

<p>... when scanning negs (medium or 4x5) past 2000 dpi the differences in quality become imperceptible. Would you say that's generally true ...</p>

</blockquote>

<p>It is mostly false. The same film emulsion at different film sizes (be it 135, 120, 4x5 or whatever) has the same recording characteristics - the same MTF curve, the same grain characteristics, the same everything. Practically and to a first order, it's generally acceptable to digitize at lower resolution for larger formats primarily because the amount of enlargement to print is lower.</p>

 

<blockquote>

<p>I find it kind of curious that the imacon 848 has different resolutions per film size, from 8000dpi at 35mm and 2040dpi at 4x5 ...</p>

</blockquote>

<p>It's a limitation of this particular scanner. The CCD imager is wide enough to cover 120 film. It isn't wide enough to cover 4x5 and has to be mechanically backed off. Simply, it's the same number of photosites covering both 120 or 4x5 - a bigger area of coverage means lower coverage density.</p>

 

<blockquote>

<p>Are the numbers for 35mm bloated?</p>

</blockquote>

<p>You mean 8000dpi? No - for TechPan. Yes, if you're thinking Tri-X.</p>

[david_henderson]

<p>As others indicate the resolution of the scan varies with film size because it makes the scanner easier and cheaper to produce. The thing that makes this acceptable is that enlargement is often smaller from a larger film size.</p>

<ul>

<li>Is there any point canning at a higher resolution than 2000<em><strong>ppi</strong></em>? Mostly yes. There is generally more detail than that in a piece of film of whatever size, although what it does contain depends a lot on subject matter, a lot on how steadily the camera was held, and somewhat on film type. If 2000ppi was the effective limit for film, then we'd all have Epson 700s and be happy.</li>

<li>In many cases, and subject to the points above it will be well worth while increasing scan resolution from 2000 to 3000 ppi. on medium format, assuming also that your appication can use the extra detail. For example not much point in scanning a MF frame at 3000ppi if you're aiming to put the result on a computer screen only. Therefore it may not be worthwhile scanning everything you take at highest available resolution. </li>

<li>Rob Garssons last post seems to be confusing measurements per unit of size (eg 2000ppi) with overall size of scan. When a scans dimensions increase it gets bigger by doing the same thing over a larger area. In fact as Mr Lee informs you, sometimes the scanner has to offer a reduced resolution at larger sizes.</li>

</ul>