Vuescan final image size

<p>Hi Guys,</p>

<p>I just cannot find any relevant post concerning this and feeling lost that i cannot figure it out how to correctly set my final image size, resolution. <br>

First of all, my settings:<br>

Input tab: Scan dpi: 2400, Bits per pixel: 48 bit RGB, Auto save: Scan<br>

Output tab: Printed size: Scan size, Tiff file ticked, TIFF size reduction: 1, Tiff file type: 48 bit RGB, Tiff compression: ON<br>

I'm scanning 35mm negative film. Final pixel size: 3252x2168, File size 42,6 MB<br>

So, I've got a huge file with a relatively low resolution. I tried to play around with all the settings in input and output tab, but couldn't find the solution. <br>

Could you let me know how to set my final image size properly? <br>

Thanks,</p>

<p>What were you expecting to get out of it? The scan size is not far off. 35mm frames are 36mm wide x 24mm tall (1.42" x 0.94"), just less than an inch tall, so with a little cropping on the scan (maybe to remove the hard edge of the frame or a slide holder shadow), 2168 pixels on the short dimension is not unreasonable. You are saving in 48-bit TIFF, or 6 bytes of color information per pixel. Doing the math, 3,252x2,168 is 7,050,336 pixels for the image, times 6 bytes, is over 42 megabytes for the image. Allowing for TIFF and file system overhead, and everything seems about right on the money.</p>

<p>If you want a larger pixel size, you'll need to raise the "Scan DPI" above 2400. However, you need to be careful there, as if you go above the scanners native ability, you may find undesirable results. Many scanners advertise 4800 DPI, even higher, but the scanner device often isn't capable of that many pixels natively, so the scanner software (or VueScan) interpolates the in-between pixels.</p>

<p>If you want a smaller file size, you can either lower the scan DPI (probably not what you want), or choose a lower color depth for the TIFF file, like 16bits, which would give you a file size around 14MB.</p>

<p>Vuescan won't let you go above the scanners native dpi, or at least the native dpi is the largest preset value that you can choose.<br>

48 bit RGB will produce a file sized much larger than a 24 bit RGB file.<br>

If you want to reduce the pixel count then Tiff size reduction of 2 would halve the pixel count. I'm not sure what 3 would do but I do know you can't set a non-whole number.<br>

Tiff compression is compressing the file, you lose some quality, and if your pixel count is already sub-par you'll notice it quite readily. No compression will produce a larger file size, but once you convert the file to a jpeg it will be more manageable.<br>

The low resolution may be an affect of the actual scanner you're using. Scanner manufacturers put out their numbers in absolutes, 2400dpi, 4800dpi, etc... yet will never tell you that that's just what the sensor picks up. What the lens in the scanner delivers to the sensor to pick up is another thing entirely. Most flatbed scanners have an effective pixel count of about half of the actual pixel count (generally speaking, some are better and some are a lot worse).</p>

<p>Assuming you're not maxing out on your dpi change these values-<br>

Input tab: maximum dpi, Bits per pixel: 24 bit RGB, <br>

Output tab: Tiff size reduction 2, Tiff file type 24 bit RGB, Tiff compression off</p>

<p>Now this will increase your scan times, but (assuming you have a 4800 dpi scanner) it will give you the same pixel size output but it will be sharper and being 24 bit will be much smaller in size. You can turn the tiff size reduction back to 1 if you'd like larger images than what 2 gives you, then reduce the size in post processing to whatever you want.</p>

<p>A scan of a 35mm slide (24x36mm) at 4000ppi will yield a image that is 5352x3668 pixels, roughly, depending on cropping of the original in scanning. The <strong>size of the image in <em>pixels</em></strong> is determined by the scan density (e.g., 3200 ppi, 4000 ppi, 9600 ppi).<br>

If you set the Vuescan "Printed Scan" size to 8x10", then the final image in the case above will set the maximum dimension to the 10" so the image as it comes out of the scanner and in the file, will be 6.8" by 9.985" which is as close as can be got to 8x10 with the image from the slide. This translates to a "resolution" of 536 pixels per inch.</p>

<p>But that isn't important, all that counts is the ppi size. If you <strong>resample</strong> to 13x20", the resulting image resolution will be at 267.6 pixels per inch, but the SIZE OF THE IMAGE WILL <em>STILL</em> BE 3668 X 5352 PIXELS. This sort of resetting is important when you print, but is not important until you print.</p>

<p>I think what you're looking for is the (printing) dpi. If so, that's on the Output Tab.</p>

<p>So, I've got a huge file with a relatively low resolution</p>

<p>I think you're unclear on the difference between scanning dpi and printing dpi. Try zooming in with some image viewer or Photoshop, till you're at 100% viewing ratio. That'll give you a feel for your image size. If you've got a huge file, you've likely got lots of pixels. Check the x and y pixel dimensions.</p>

<p>BTW, unless things have changed: do not do any downsampling with Vuescan. It uses a method similar to "Nearest Neighbour" (in Photoshop). Photoshop's biCubic does a better job. Vuescan downsampling messes up fine detail.</p>

<p>Thanks guys for the replies (i was away on a trip, i can just now reply). <br>

You enlightened me in a lot of aspects for, but new questions popped up. <br>

So. Until recently i used 24 bit both on the input and output tab. But i read on the forums that it should be 48 bit as it gives better quality.<br>

My pictures are going to the web almost always, but i want them stored in an appropriate file size which will be good enough for larger prints if needed. It's important for me, because after having scanned the negs i make some basic editing in Aperture. So i don't want to scan the files later on again if i need a bigger size and i wont be able reproduce the exact same colours. That's why i want to control the resolution, details as much as i can. <br>

On the other side i want to avoid extreme file sizes. Now, I'm a little confused about the optimal dpi, resolution. (I've got a V700 which has 6400 dpi on paper.)<br>

It is also not quite clear what's the difference between the input and output dpi? I mean if i set 48bit for input and 24 bit for output for example.</p>

<p>Flatbed (scanning) dpi is a grey area. With dedicated film scanners, with holders, a transport system, and lens, the professed dpi is pretty much as advertised. But with flatbed you have to take the numbers with some skepticism. The scanner will deliver a file with the pixel dimensions that agree with the dpi, but in most case the higher dpi's aren't really getting more detail.</p>

<p>I'd hazard a guess with yours that somewhere between 2400 and 3200 is the practical limit, ie: scan higher than that and the results won't be much different then scanning (say) at 2400 and upsampliing. The numbers I threw out are just guesses though, maybe other users of your scanner will weigh in.</p>

<p>You can test it yourself, by scanning at different resolutions, then upsampling the lower res to match the higher, and comparing visually: is there any additional detail?</p>