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07/12/2002 07:23:32 PM · #1 |
One of the Challenge Suggestion threads got me thinking (yes, there's a first for everything!) about printing and "the photo processing" prints. The more I think about it, the more confused I get. Many, many moons ago, I played with photo processing with real film. To make a print, I took the negative to a projector unit that shot light through my negative to the target (photo paper). If I moved the optics further away from the paper, the image got bigger. Seems pretty clear to me. Now, I'm into digital, no film, and print most of my stuff on a pretty nice ink jet printer. I "get" the idea that more data (larger file sizes) can be printed in larger formats. My first digi-cam max'ed out at 320x200, very small prints before pixelation killed them.
Long sigh......
With that huge preface (I hope somebody has the patience to read this!)
Now comes the parts I don't "get". I have taken my 2250x1800 photos and sent them to ink jet plotters at ANSI C, with little or no pixelation. What makes the difference between a desktop inkjet printer and a plotter inkjet appliance? (Why can I print BIG on a plotter and not on a desk printer?) Next, if these web sites that offer photo prints are using a photo processes, why can't they move the optics further back and print HUGE without pixelation?
Which leads me to another related idea that I have never tried to afford. (Space, money and chemicals) If I took an LCD Projector with an image displayed on the wall, providing that I could work in the dark, why couldn't I place an unexposed piece of unexposed photo paper, place it on the wall, open the projector to the screen for the correct number of seconds, develope the paper....Wouldn't this work to make giant photo "prints"? If no, why not?
Thanks for any with the patience to read this, tackle as much or as little as you can. I am really interested in this idea/subject!
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07/12/2002 09:04:35 PM · #2 |
Swash,
What do you mean by big?
With a 2250x1800, you should be able to get a 10x12in image with a little interpolation, and probably even 11x14 if the photo is very sharp.
For inkjets, 200dpi is considered minimun for photo quality.
What is the prefered image resolution for jet plotters?
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07/12/2002 10:45:10 PM · #3 |
Originally posted by Swashbuckler:
I have taken my 2250x1800 photos and sent them to ink jet plotters at ANSI C, with little or no pixelation. What makes the difference between a desktop inkjet printer and a plotter inkjet appliance? (Why can I print BIG on a plotter and not on a desk printer?)
A Guess: The plotter prints each pixel as its own little spot of ink. Printers for desktop publishing usually assemble the pixels into (halftone dots) which are much coarser (typically 90/inch vs. 300). But it could be something else entirely.
Next, if these web sites that offer photo prints are using a photo processes, why can't they move the optics further back and print HUGE without pixelation?
I believe those photo printers also "plot" each pixel as a laser spot hitting the paper. I don't know if they use three different color lasers, or one laser with a series of three filters. If you were to shine those spots through a magnifier/enlarger, each spot would just get bigger -- exactly the same thing as pixelation on a printer/screen. You get that (eventually) with film, too, only it's called grain (I'm sure you know more about this with your film experience). It's my understanding that ASA 100 film (35mm) has a grain size approximately equal to 8000 dpi -- if you enlarge a 35mm negative a few hundred tims (e.g. make a 20x30 print) you will see the individual gelatin granules, and if you enlarge further, you just get bigger spots, but no more detail. We used to image 35mm sides where I work; at 4000 dpi we used a file 2048x1366 pixels (about 8MB in RGB), for 8000 dpi the dimensions doubled (4096x2730 pixels, 32MB). At that, I think each pixel served two scan lines... The photo printers "native" resolution seems to be 300 dpi. I would use that, or an integral factor (e.g. 200, 150). I have had one 20x30 made from a 2000x3000 pixel file and it looks kinda grainy (it was a low-light photo anyway) but not pixelized (no little squares). My current plan is to make the largest prints by re-sampling the image up in Photoshop. That way I can see how much enlarging will affect the image, and maybe compensate some (re-sharpening is usually needed). I think that's better than letting someone else enlarge it.
Which leads me to another related idea that I have never tried to afford. (Space, money and chemicals) If I took an LCD Projector with an image displayed on the wall, providing that I could work in the dark, why couldn't I place an unexposed piece of unexposed photo paper, place it on the wall, open the projector to the screen for the correct number of seconds, develope the paper....Wouldn't this work to make giant photo "prints"? If no, why not?
This should work, but first take a close look at the image made by those projectors. Not only are they limited to a relatively small number of pixels, but on the one's I've seen the pixels always seem to be jumping or "swimming" around (remember each pixel is actually flashing on and off about 75 times/second) -- I think you'd get a fuzzy print. An alternative way to make an extra-large prints (or many copies) is to have your file sent to standard 35mm negative (only costs a couple of bucks) or a 4x5" sheet negative (I think about $25) and have "traditional" prints made from that. But you'll still need a ton of pixels... |
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07/13/2002 01:53:30 AM · #4 |
Now comes the parts I don't "get". I have taken my 2250x1800 photos and sent them to ink jet plotters at ANSI C, with little or no pixelation. What makes the difference between a desktop inkjet printer and a plotter inkjet appliance? (Why can I print BIG on a plotter and not on a desk printer?) Next, if these web sites that offer photo prints are using a photo processes, why can't they move the optics further back and print HUGE without pixelation?
Hey Swashbuckler
Simply put, a Raster Image Processor or RIP, is the "thing" that goes between your computer and printer containing the material you want to print onto. It allows the translation of the image in your graphics program into a series of dots that your printer or plotter either fills in or leaves blank, thus creating the desired output. This is called "PostScript interpretation". This âRIPâ, can be either a hardware or software device. This translation of image is what makes it possible to print a small image on your home printer and print the same picture considerably larger on a large format printer with no additional bitmapping or distortion of the image. texttext |
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07/13/2002 02:52:49 AM · #5 |
Originally posted by Gotcha:
Simply put, a Raster Image Processor or RIP, is the "thing" that goes between your computer and printer containing the material you want to print onto. It allows the translation of the image in your graphics program into a series of dots that your printer or plotter either fills in or leaves blank, thus creating the desired output. This is called "PostScript interpretation". This âRIPâ, can be either a hardware or software device. This translation of image is what makes it possible to print a small image on your home printer and print the same picture considerably larger on a large format printer with no additional bitmapping or distortion of the image.
This is true only of printers running Adobe's PostScript language. Many (most) printers, such as HP, use a different (but I'm sure similar) page description language. HOWEVER, scalability of even PostScript graphics is limited to "vector-based" images: those drawn by defining a line or area with a mathematical formula, and then applying color and effects to it. A raster- or pixel-based image (scan, digital photo or video) has exactly the same scalability limitations as a TIFF, JPEG, or any other format, even if it is "Encapsulated" within a chunk of PostScript code.
If you have to enlarge a digital photo, you're still best off doing it in Photoshop (or equivalent) where you can see (and modify) the effect of the enlargement.
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07/13/2002 03:09:49 AM · #6 |
Most all Large format printers have a RIP that is compatible with multiple graphics programs and files. This is from the HP web sight:
The HP DesignJet 10ps graphics printer delivers fast, color-accurate, photo-quality comps and proofs with the look and feel of offset prints. Designed for graphics professionals, the printer comes complete with Adobe PostScript 3 RIP for personal use. Features: Six-color, 2400 dpi writing system...
But you are good Paul.... Your damn good. |
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07/13/2002 03:13:31 AM · #7 |
O.K., I had to rethink this a couple times, but now I got it, no, well, maybe. O.K.
I don't know post script or RIP, except that it is something between the print command and the printer. As for the LCD Projector idea, I knew it had to have problems, it was too simple to work well. I hadn't thought about the screen refresh. I have a lot of bad ideas, but every once in a while the moon does show somewhat blue. General, you the man! What would you consider to be an overly big file? Gotcha, thanks, well put. Zeiss - BIG, ANSI C is about 20x24. Me, I want giant life size poster BIG. Don't ask me why, I think big, then find reality someplace below.
Bottom line: I want to see my stuff on a billboard! |
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07/13/2002 03:15:18 AM · #8 |
Paul (GeneralE) Do you know much about fractal software programs for enlarging digital photos to huge sizes without distortion??
I'll be in Concord Mon. & Tue.... Dinner is on me. |
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07/13/2002 03:21:39 AM · #9 |
| A big file to most of the people in my world would be a Gigabyte and a half. This would produce a life-size picture of a human, (72"). When you are talking about a billboard.... well, they can run in the neighborhood of a couple of terabytes. |
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