Grain aliasing when drum scanning newer ISO 100 color neg film

<p>I'm trying to figure out how much of a consideration this is, or should be. I have a project I'll be shooting on color (120) film and then drum scanning, and I'd like to use color negative rather than transparency film.</p>

<p>This page strongly recommends that if you need a 4000dpi scan, to avoid GA one should scan at 8000 spi ("samples per inch" is the term they use) and then downrez it to 4000 rather than scanning at 4000 (see middle pair of photos to see the GA they describe on the latter):</p>

<p>http://www.drumscanning.com/rab.html</p>

<p>This page (same vendor) says grain aliasing is more of a problem with negative films than transparency films:</p>

<p>http://www.drumscanning.com/krrab.html</p>

<p>This page says (near the bottom, in section called "What can be done about aliasing") that "Using film of reputable manufacture and modest ISO speed will minimize any risk of aliasing":</p>

<p>http://www.photoscientia.co.uk/Grain.htm<br /> <br /> But that last page was written in 2000, and a decade later I don't know how relevant it still is with regard to films like Kodak's new Ektar 100, which - one would presume - would be designed to minimize GA if that's possible.<br /> <br /> <strong>It matters to me because</strong> an 8000spi scan costs almost as twice as much as a 4000spi scan and that adds up. Yes, the easy way to be sure is to try, so I'll probably have a frame of Ektar scanned at 8000 (then downrezzed to 4000) and then rescanned at 4000 so I can compare those two 4000dpi files. But before I spend the $150 for those two scans I thought I'd float it here (didn't put this in DigiDarkroom forum because I thought filmies would be less likely to see it there).</p>

<p>TIA.</p>

<p>I don't know if I will be of any help or not. I scan on an the Imacon(hasselbald) flextight and mostly 4x5 and 2-1/4 at about 3200dpi max. I scan mostly neg films and have only had a similar issue when I have scanned b/w negs. In that case, it was before I was scanning everything at 16 bit. Once I changed to a 16 bit scan, the problem disappeared--as did many other issues in post!</p>

<p>Grain aliasing for me has been unpredictable with my flatbed scanner, even on the same roll of film. Before you start your project in earnest you ought to test color transparency and color negative films, no matter what advice you get. Use the subject matter, materials, and process as on your project, and then you will be sure of the right choice.</p>

<p>The reason to use higher resolution in scanning is so that the lens serves as the required optical low pass filter.<br>

The grain on Ektar 100 may be so fine it's not a risk of grain aliasing. The risk comes when the grain is about the same "dot pitch" as the scan is at, that's when you get the "beats" that cause grain aliasing.<br>

Wise advice is to talk to the folks who run the drum scanner service you're using, and see what they say.</p>

<p>The examples they show all have pretty ugly (to my eye) color noise, and I'd want to apply noise reduction before printing. In general, scanning at a higher resolution, applying noise reduction at the higher resolution, and then downsampling should result in cleaner and/or sharper images than scanning at the lower resolution and applying noise resolution directly. I find I much prefer scans of slide films to negative films, but there's a lot of personal preference here. Shoot a test roll of Ektar 100 and of Provia 100F, pick the sharpest 2 or 3 frames from each and get 4000 and 8000 ppi test scans and figure out how to best produce the desired print quality. Check the frames carefully with at least a 20x loupe, if not a 60x microscope, before spending money on scans.</p>

<p>FWIW, the worst grain aliasing I've seen has been consumer color negative films scanned at 2800 ppi, and the most improvement I've seen is by moving to a 4000 ppi scan for those films. So my bet is that you may not see much of a difference. Dealing with 8000 ppi scans of medium format on any computer you can afford will be seriously painful.</p>