Epson Ink Target

[Vicki Patolot]

Im using an epson perfection V750 PRO to scan medium format black and white negatives and cannot find an answer to a question that I have. Here it goes...my digital imaging teacher (Allison Hahn) told me that the best way to scan my negatives (and she's a pretty qualified scanner expert if you look her up) IF i know what size I want to print them at, to scan only at 300dpi but set the 'target size' to the size I want my print to be. For example, our epson printers here at school print at 300dpi, so if I know I want my final print to be 15inches by 15inches, I should scan my negative at 300dpi and set the target size to 15 by 15 inches.

Now, I have a lab tech here at school who says this is a bunch of b.s. and told me to scan my negatives at a really high resolution and to resize to my 15 by 15 inches later. So, I scanned at 2400 dpi at 'origional' target size. I then resized the image and zoomed way in on one part of the negative. Result, the 300 dpi scan had wayyy less pixelation than the 2400 dpi scan and looked sharper and better.

But, the lab tech described to me that even though the 300 dpi scan (with the 15 inch target size) looked better, the 2400 dpi scan was way bigger and thus had way more information to work with if I for example needed to heavily edit the image.

Scanning for 15x15 inches at 300dpi is already high res - 4500 by 4500 pixels in the resulting scan - 20 megapixels. It's not necessarily maxed out, but it's not a typical scenario where one would necessarily recommend scanning higher and then reducing (and sharpening) just to increase final quality. One reason to scan higher would be if it was going to be your permanent archive for a given photo, and you want to scan once and color correct once, and utilize the max resolution possible in creating your archive.

On this point:

Here you're confusing scan/image res and print res. There are really three things

(1) You scan at a given dpi - the scanner generates a certain number of pixels per inch of your orignal material

(2) Read this a few times to make sure you get it - Your resulting image has its own dpi, which can be changed in programs like Photoshop, that says given the "pixels dimensions" of the image (how many pixels wide and tall it is), how do you want to concentrate/distribute them? This is just redistributing pixels.

Your 15x15 @300dpi scan will be 4500x4500 pixels (15x300). Set the dpi of the image (in Photoshop, after your scan) to 1dpi and your print will 4,500 inches, set it to 4,500 dpi and your print will be 1 inch, set it to 100 dpi and your print will be 45 inches. To simply redistribute pixels when changing dpi, you uncheck "resample" in Photoshop. With resample checked you're actually adding or subtracting pixels and changing the overall pixel dimensions.

(3) Finally, the printer has it's own dpi for the print it's making. For an inkjet it might 300, 600, 1200, but that's a printer thing.

I absolutely HATE the way some software handles this terminology. The only PPI value to worry about with the scanner is the points per inch of the negative being scanned. Your scanner can reasonably be set at 3000PPI. Your negative has a 2.25"x2.25" image area. So you can get up to 6750x6750 pixels. This is excessive for most uses, so say you run it at 2000PPI and get 4500x4500PPI.

3. Is printing the only destination, or are you viewing on-screen? Do you want to pull out all the detail your scanner is capable of, or do you want to stop at that printing requirement? Likely the two requirements are close, but it's something to consider.

Say your negatives are 2.25" square, and you settle on 240 dpi for printing, and your max size ever will be 15" square, and you don't care if there is more potential detail that could be scanned, then should set the Pixels-Per-Inch of your scanner to be:

Now, if you want to view your scans on-screen, and you want to get all the detail your film contains and/or use the full potential of your scanner, all this goes out the window. Then, I'd say scan your film at various Pixels Per Inch, increasing the value until you no longer see additional real data being resolved. Then scan at that resolution in future.

Maybe I'm just not getting the point, but did you answer my question? So what IS better, scanning at 300 dpi(on the epson menu it says dpi, NOT ppi) with a target size of 15 by 15, or scanning at 2400, 3200 whatever and then resizing to 15 by 15 later?? And my scanner actually goes up to 12800 so should i scan at that?

Chris; scan the 2x2 inch original at about the max the scanner really puts out; say 3200 dpi. Then use this image for your prints,.With all the time it takes with scanning; just scan the original once.

The target scheme method is flawed. If you only wanted a 6x6 print your would be scanning the 2x2" original at only 600 dpi; then to do a 12x12 print you would have to rescan it again. Scanning takes time; few folks scan a negative 3 times to make 3 different sized prints. Time has to be spend making sure the negative is dust free; getting it the correct way up; doing a pre scan; saving the file.

The DPI thing vs PPI thing is a constant annoyance, the correct term is PPI but everybody says DPI anyway. DPI is actually a measure of how many ink drops per inch your printer can lay down, and since it takes many drops to make a color, the more DPI your printer has the better and smoother its color reproduction. If my printer is 2880DPI and I have it print a 180DPI image, each pixel of the image will be formed with a 16x16 set of ink droplets, which is a lot.

You take the film size and multiply it by the scanner resolution to get the pixel dimensions of the scanned image. None of this "target size" business - I say that because it causes your brain to go in the wrong direction. PPI is a value that relates only to interfacing a computer with an image in the physical world. If you have a 2.25"x2.25" negative and scan it at 2000PPI, you get a 4500x4500 pixel image. That is an appropriate use of the concept of PPI. It's better to do that math in your head than to use the software's target size function, because it forces you to understand exactly what it's doing and because the PPI of the scanning is an important thing to know. If you do know the desired print size and resolution, do that calculation in your head too to decide how many pixels you need then work backward to the scan resolution.

Now you have the image, it's 4500x4500, and forget PPI. Forget it completely, it doesn't exist, your image is a collection of pixels that have no relation to inches because they don't exist in real space. Photoshop says it has a size in inches and a pixels/inch value, but it's lying because it hates you and it's part of a conspiracy to confuse you.

Now, do whatever work you are going to do on your digital image file, and when you're ready to print it, print it. Set up the paper size in Photoshop and use Scale To Fit Media. Photoshop will now inform you what your PPI is, and it will be telling you the truth, because it's about to put your image into the real world and therefore your image can have a PPI value.

This may seem more complicated, and it does involve doing math, but when you think of it in these steps you will find your understanding of the issues functions at a higher level. You will also know that when, for example, you ask the woman at Ritz Camera what resolution she will scan your negatives at and she says "300 DPI", what she just said makes no sense, and when she clarifies that she's talking about 300DPI for a 4x6 print, she is talking about a pathetic 2 megapixel scan (1200x1800, which you'll figure out in your head in real time) and you need the premium service which comes out closer to 9 megapixels.

BTW the PPI you need for your final print will depend largely on how far away the viewer will be from the print. 240 is fine because a 15"x15" print is put on the wall and viewed from a couple feet. A 4x6 is held in hand close to the eye and should ideally be at 300. The larger the image, the further away it will be viewed from and the lower the PPI requirements. Billboards are often printed at 2 PPI. 1080P HDTV is 2 megapixels and nobody says it's low res. 720P is 0.9 megapixels.

Then the real question is do you really need 300ppi image at the end? printing on a inkjet? epson? 150-200 will do perfectly...making your 2400ppi a too big number for nothing, while 1200 could have done it.

Your teacher suck at explaining the concept correctly, your lab tech suck as what he said is exactly the same thing as your teacher using different number only, and you probably suck as not undertanding correctly both of them maybe..the good news, i had time to help you sleep tonight knowing a little trick to calculate everything all by yourself now ; )

The only difference is when you begin a print process, the default starting point for print size will be different, but you can change that in a blink. The shortcoming is in the program. Vuescan, for comparison, will ask two questions: what ppi do you want, and what's your preferred printing dpi.

Lets say that your scanner has a native resolution of 4800 dpi. Unless you had a good reason to not scan to it's fullest ability (it slows things down considerably and you have a lot of work to get through for example) then scanning at it's fullest capability isn't going to hurt anything except your disk space. Your printer will still print it just fine, and if you decide to photoshop it you have more to work with. Anything over your native resolution is going past the point of diminished returns. You get less back than what you are putting into it. So if your scanner states two different resolutions, go for the native or optical or the non-interpolated resolution.

With the V750; V500 and 2450 and 3200 Epsons; I consider their native resolution to be settings I can really use that work and actually pull our USEFULL detail; ie in the 2400 to 3200 dpi area. Folks that are gullible often believe specs about what a scanners max resolution is. Here since I have done scanning for 20+ years I prefer to do my own tests; each of the dozen plus flatbeds is tested. Thus with an old pro 1200 dpi scanner that cost 3 grand that has 4800 dpi settings; it is BS beyond 1200. It that era scanners were mostly marketed to service bureaus and pros. Today most scanners are bought by amateurs; thus the fluff factor and BIG numbers are used; like marketing speakers and boom boxes.

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