Pretty good summary Randy... and also... Just remember to put the paper in the right way round otherwise you get an upside-down print.
On Sun, Mar 19, 2017 at 5:02 PM Randy Little <randyslittle@xxxxxxxxx> wrote:
Well what fun is that Herschel. geez. Printer smart makes up dots. printer only so smart adding lots of dots makes soft image. ;-)On Sun, Mar 19, 2017 at 6:58 PM, Herschel Mair <herschphoto@xxxxxxxxx> wrote:If you're interested in this technology and want to know what the Catmull-Rom spline curve is all about, I can recommend:However, the best way to know how your print will look on a given printer, at a given size and resolution is to make the print. No amount of technical knowledge will give you a better answer and if your printer is interpolating using all kinds of curves, vectors and tangents... well there's not much you can do to change it anyway.My 2c worth... just to irritate the technicians.On Sun, Mar 19, 2017 at 4:17 PM Randy Little <randyslittle@xxxxxxxxx> wrote:what the printer does it interpolate the image to fit its needed resolution at the print head. it does this in a crude way first. Literally saying ok I have pixel one at this value and pixel 2 at this value and I need 10 more pixels in between. Those pixels need to transition from pixel color 1 to pixel color 2 over those 10 (or whatever) pixels. Now there are all kinds of option as to how many pixels to evaluate fron literally the only the pixels that touch a single pixel to convolutions to thousands of pixels. Safe bet is that they only just apply cubic interpolation and maybe michelle or Lanzcos. I doubt printers are going any crazier to more intense math like SinC or Catmull Rom.
FYI the printer rip does this no matter what the resolution up or down as until it hits the RIP and is converted to 9-12-18 or just 4 colors you can't set your file to be what it wants inside normal human being world. We can only get close. Its is why its a good idea to set your files to a perfect divisible number to the printers dpi. It makes all the match work better.On Sun, Mar 19, 2017 at 5:18 PM, karl shah-jenner <shahjen@xxxxxxxxxxxx> wrote:Kostas:>Karl can you alaboarate on these points?.. hardware rips even more so, except that printers themselves have RIPs onboard that often can do the job surprisingly well.The prinetr it's self will apply the algorythms and fuzzy logic required to upsize the image and produce the best image it can without pixellation.Do all printers use this?Hi Kostas. Yes as far as I know these days all printers and the software that comes with them have this ability. In the past some or many printers needed all the specific information fed to them in their language as to what was to be done in making a print.. if the image fed to it was 300 x 300 pixels and the printer printed at 300 pixels per inch resolution than all you could get out of the printer was a 300 pixel or a 1 inch image. Any upsizing done in the printer settings (say if you said make it 10 inches in size) resulted in a 10 inch image, but each inch contained blocks of 30 pixels - and visible pixelation. So a diagonal line from the bottom left corner to the top right would have looked like stairs.RIPs (raster image processors) are made for many purposes, For example architectural RIPs are designed for precise scaling, so the upsized image will show no linear distortion and measuring off a plan will be as accurate as calculating from the original numeric specifications. Some RIPs for graphic design are designed to produce the most accurate colour renderings using the specific print known inks of a known printer (4 color type like used in magazine or carton printing) . Our photographic printers use this too, especially since each printer has it's own special inks these days rather than in the previous example where inks came in tins like house paint. So our photo printer RIPS are tuned to take a RGB or CMYK colour and render it accurately with an ink set that might be (using a 6 colour canon as an example) C lC M lM Y K, Other printer RIPS are designed for greyscale printing and without the need to desaturate an image in your software, the full colour image can be fed to the printer through the software RIP that knows how to best render the colours into a natural looking greyscale*.*I should say 'natural looking' is a bit of sales pitch since eyes interpret colour adtones differently - this is a complicated area for another time, but think of it like this, black and white films had different colour sensitivities.. so which was the most natural, FP4 or T-Max? - red, blue and green were rendered differently by each of these films ..But one of the most useful things in modern printers is the interpolation of the image in upsizing.. so sending a 300 pixel image to a printer and saying 'make this 10 inches long' rather than showing blocky pixels as happened before, the print driver applies whatever upsizing algorithms it has in the program to the job and seeing that line from bottom left to top right in the example above, it preserves that detail and gives you an image with a line rather than stairs. We take this all for granted now but not long ago this would have been considered pretty much magical. In fact we take it so juch for granted we often don't look when we compare printers to see whether one brand does a better job than another brand at this sort of upsizing, we just assume they're all good as one another - but different brands use different RIPS .. I've never compared or tested them though.It's a bit like the fight for automation in cameras - consumer cameras had auto settings, the camera that took the best pictures automatically was the one consumers wanted, it got so good that almost all pictures from all cameras looked good - so not many people stopped to compare what or how the automation varied, or tried to find when or why one camera took better images than another under conditions that might push the cameras automation.. they just went 'oh that one didn't work' when the automation failed.Often this ability (the RIP at work) is mistaken for a dpi setting below the normal quality barrier (300 ppi) - it's not usign a lower ppi at all but rather an interpolation programmed into the printer.here i have lost you....Sorry ;) You know photo printers have high DPI settings, say 4800 dpi.. so up to 4800 dots of whatever ink are needed are squirted out to make the fine gradation of colours and tones. That's the sales guys taking the technical specifications and using them to impress customers. Sure it's lots of dots, but so what? OK more is better but only up to a point where we can differentiate it's not that relevant to us really. you'd be hard pressed to see the difference in the colour range produced by a 1200 dot printer over a 4800 dot printer. Unfortunately throwing those numbers around can confuse people .. really we only need to know a couple of things and that's the number of pixels per inch we can differentiate (usually 300 at normal viewing distance) and the size of the image we need to make a good print.It's true for a wall sized image a lower number of pixels can be used per inch as you'll stand back further to look at it - BUT think of any large picture you've seen lately, is it pixelated when you get up close? These days I'd doubt it.. If we were printing with only a basic RIP or without a RIP of any kind like older printers did, printing at 50 ppi you'd easily see blocks as the pixels grew larger - you'd see those 50 little squares across an inch.even at 200 pixels per inch at normal viewing distance pixels can be noticed, that's why we went for 300 .. it's really hard to see 300 little blocks across an inch but someone with good eyes could spot a 180-200 ppi print was made up of little blocky square pixels - but this doesn't happen any more because again the printer RIP actually does some interpolating and resizing when we scale the image to lower settings that 300.Nowdays when a printer is fed a 300 pixel (one inch) image and told to make it 6 inches across, rather than seeing a 50 pixel per inch image with noticeable blocks the printer smooths it out and - yes sure it may look a little fuzzy - but there's no pixels visible. This is what I meant in the comment above - it can lead people to think that it's OK to print at 50 ppi and that 50 ppi is what they're getting. the image was sent at 50 ppi, but the printer is really just upsizing that image to a fuzzier, larger image at an effecive 300 ppi (it knows what 'the good' setting is)Sure it'll look OK at distance but again the RIP automation has taken over and done the hard work with no thinking involved from us and we can misunderstand what we're seeing. End result itll look fine (or not) but it's not really a 50 ppi image.. that's just what the RIP had to work with before it did it's magic. A better way to think of it would be 'my printer can make a pretty good 8x10 image print from a 400x500 pixel image' rather than thinking of it as printing a 50ppi image.Since we're photographers and we're trying to make the best images we can then aiming for 300 ppi at normal viewing distance is what we try to do as even the fussiest eyes will see that as smooth.These days with so much automation in everything it can be tricky knowing what's going on - sometimes it almost doesn't seem worth trying to understand when the results can seem so good, but it's like automation in cars - everything is great when it works.Στις 4:46 μ.μ. Τρίτη, 7 Μαρτίου 2017, ο/η JW Faul <nyce2jan@xxxxxxxxx> έγραψε:
Roughly 4x5”
On Mar 6, 2017, at 5:28 PM, Lea Murphy <lea@xxxxxxxxxxxxx> wrote:
I have a client with a jpg that is 1770 x 2041 at 75 ppi.How large a print can she make from that and expect to get decent quality?
Art FaulThe Artist Formerly Known as Prints------Stills That Move: http://www.artfaul.comCamera Works - The Washington Post
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