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Resolution

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  #1  
Old 11-02-2003, 04:43 PM
Old Phogey Old Phogey is offline
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Resolution

New to digital photography, and new to this forum. My main interest is in B&W (ex-old hand at film), with some interest in colour. My immediate query is concerning inkjet printers, resolution, and final print size. My recently aquired camera has a max. picture size of 2592 x 1944 pixels. Using the calculation evident in the table on p268 of my copy of the Hidden Elements book, this would equate to a 'max final size for photo quality (200dpi)' of around 13" x 9.7". OK, easy. Now looking at the table on p 271, if I were to buy a printer at say a resolution of 4800 x 1200 dpi (and using the lower figure, a true resolution of 1200 dpi, as indicated in the book), then this would equate to a required file resolution of 300 to 390 ppi ([1to 1.3] x dpi/4). This would (at 2592 x 1944 pixel size) give a picture size (using 350 ppi) of around 7.4" x 5.5". Not the same answer!? I need to buy a printer. On the face of it, the higher the printer resolution, the smaller the optimum print size - is this right? Obviously I would like to print fairly large - A4 or up to A3. Sounds like A3 out of the question, A4, well maybe. Appreciate that these are rule of thumbs, and resizing is possible, but at present don't know consequences of resizing. What resolution printer to buy? Help!
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Old 11-03-2003, 09:40 AM
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Richard_Lynch Richard_Lynch is offline
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Quote:
On the face of it, the higher the printer resolution, the smaller the optimum print size - is this right?
Yessir. Keep in mind that it is also 'optimal'. You can ignore optimal settings, and still get some decent prints. The idea from my end was to tell you what you really needed to make the most of your printer's capability. That is...you want to give it the right amount of information. If you don't, you may be selling the results a little short. However, there also comes a point where human perception will fail, and it may very well be that the difference will not be something you can see (without a magnifying glass).

The key is to understand the trade-off. From what you said, it seems to me that you do.

Richard
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Old 11-03-2003, 10:50 AM
kudbegud kudbegud is offline
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in a recent dpreview sony talk forum thread this issue was thoroughly covered. its a long thread but very informative. pay particular attention to the responses by Peter iNova. he has done test printing at different ppi/dpi resolutions and his conclusion is that you can print at 180 to 220 and get photo quality prints. another response suggests that you let your editor choose the ppi by unchecking the re-inturpolate box and putting in the required print size. using your full resolution photo, i think you will get the size you need...a3 or bigger.
http://forums.dpreview.com/forums/re...essage=6396439
and dont forget, the 4800 x 1200 is for all the ink colors combined.
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Old 11-04-2003, 07:16 PM
Old Phogey Old Phogey is offline
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Thanks for the info and useful link. Lots of info, and will take some time to digest.
In the meantime, I appreciate that a high dpi printer requires a high resolution (high ppi) input to make the most of its capabilities. But at present my 'given' is a 2592 x 1944 pixel camera. Now say outputting at 200ppi (or 300ppi), will the print look any better on a 1200dpi printer than say a 800dpi printer? And if I resize (or rescale) to A3 size, what then at different dpi? Will a higher dpi printer always give a 'better' looking print (as it is noted is the case with monitors - p269 of the 'Hidden Power ' book)?
What I suppose is needed is a plot of 'perceived print quality' graphed against printer dpi, at some different inputs - say 150ppi, 200ppi and 300 ppi. Has anyone any idea what such a graph might look like? Or where the law of diminishing returns starts to take effect (presumably such a graph would flatten off when the eye starts to be unable to resolve further detail)?
And to stir up the mud some more, how does printing in B&W affect this?
I guess I'll go out and buy a 1200dpi printer, just need to decide on A4 max. or whether going up to A3 is worth it. Hmmm....
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Old 11-04-2003, 07:53 PM
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Richard_Lynch Richard_Lynch is offline
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ok...IF you have enough resolution where the prints will have enough to work with AND you will see the difference (can perceive) between the fineness of the two printers (a 720 is usually pretty good), then the more resolution you have in the printer, the better the print. The monitor example points out that when you can see the difference (72-96 DPI onscreen is 1/10th the resolution of 720), having more resolution will make for a better image. This works in print too as the dots that fill the spaces will be finer -- more difficult to see. Like comparing newsprint to a magazine, you have better reproduction with finer print, but there is a balance. feed the finer printer too little information, and the flaw shows in too little resolution.

GENERALLY, as you raise the resolution of your printer, you want more resolution in your image. if you are satisfied with the sharpness of a 720 DPI printer using 200 PPI images, you will be satisfied with a 1440 printer using the same image...and probably more-so with that same image bumped up in PPI and UPSIZED to give the extra resolution to fit the higher frequency. The quality does not go down as you increase printer capabilities, but your ability to descern the difference becomes finer because of the printer's ability to depict.

There is always a balance between quality extremes...you can only get so much out of a 35mm before you need a medium format. You can use 35 mm and blow it up larger than you should, but you lose apparent quality. you can shoot an image in medium format and size it down so small that it never would have mattered had you shot 35, but you can take the equivalent of 35 mm pictures. I'm betting any 1440 printer (that isn't measured that way because of additional colors) can print 720. But that 720 can never print 1440...The higher quality will always win as more versatile.

Last edited by Richard_Lynch; 11-05-2003 at 06:24 AM.
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Old 11-04-2003, 08:00 PM
Old Phogey Old Phogey is offline
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re - last post

Apologies, Kudbegud - I didn't read digest the Sony Talk thread enough before posting. I think the answers are in there (but it seems resolution is a much more complex issue than I thought). A3 printer it is, I think, and get on with using my new camera!
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Old 11-05-2003, 06:22 AM
Old Phogey Old Phogey is offline
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Thanks for your help. I didn’t know what a pixel was a few weeks ago, so the following may be complete naive rubbish (please let me know!), but this is now the (theoretical) angle I have on resolution:-
Image ppi:- Take a subject with full range of colours, tonal gradations, contrast etc. Capture this subject on a digital camera at a range of total pixel levels. Print this range of captures at constant print size (say 10” x 8”) without any resampling, using a ‘theoretically perfect’ printer (showing perfect printed pixels). Then choose the print that looks good to you, beyond which no great improvement is seen. This represents your personal photographic quality. 200ppi. is rumoured to be OK for most people – let’s say it’s OK for me. Using my 2592 x 1944 pixel camera, that comes in at a print size of 13”x 9.7”. With modest upsizing, I’m close to A3. This indicates I’m not wasting money on an A3 printer. Now printer resolution:- Take the 200ppi image, and print it out on a real-world inkjet printer at a range of dpi. again at constant print size. Look at the prints, and again find the point beyond which no great improvement is seen, again representing your personal photographic quality. Rumours of target dpi = ppi x2 to x4 are out there, giving a printer resolution of 400 to 800 dpi. beyond which there might be little benefit. 1200 or 1440 dpi might give flexibility (say when not many inks are firing).
Printer spec sorted!
Though I must say printing in B&W with only one ink still concerns me. What dpi does this represent? On a six colour printer rated at 1200 dpi, does this represent only 200 dpi? What’s the way around this, in order to get the full, even tonal gradations that give the superb modelling in good B&W prints?
PS is this post in the right section of the forum?
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Old 11-05-2003, 06:52 AM
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Richard_Lynch Richard_Lynch is offline
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Pixels per inch is not the same as dots per inch. PPI = image resolution; DPI = printer resolution. This (and more) is all discussed in The Hidden Power ( The Hidden Power of Photoshop Elements 2 ), pages 25-29. In short, the printer uses the PPI you give it to deliver in DPI form by converting image pixels to dots.

The image needs enough information for the printer to make optimal use of its capability. A 720 dpi printer can use, say 180-234 pixels per inch for optimal printing; 1440 can also use this image, but it is not optimized. However, that capability may be beyond your ability to descern difference, and the prints, using the same image, will be interpreted differently into dots...The same image on different printers with different capabilities will look: different. At some point the amount of information as PPI not only surpasses what the printer can handle, but what you can see.

If you are making prints for your own enjoyment, certainly you can do what you say and test for your ability to see difference. HOWEVER, if you are making prints for others, who may have better ability to perceive, you may want to impose other limits on your minimum PPI so more information is available for the printer to make better (read: sharper, truer) images.

In the end, the question comes about to: what are you trying to accomplish? The goal should help you set your targets. If you just want to fill an A3 sheet, and quality doesn't matter, you can do that with any printer. If you want 720 DPI quality, you need to provide enough information from the image to achieve that, and you need a printer capable of 720 DPI. If your aspirations are still higher (for refined quality) you need botha printer with more dots, and an image with more PPI. The ability to get quality may extend to what you print on (media).

I think it inaccurate to oversimplify that 720 is always good enough. Take out a lupe or magnifying glass and have a look at the difference between a 1440 print and a 720. The 1440 should appear ro have a more continuous tone. this may be more apparent in lighter tones. while continuous tone is not always a goal, the inexplicable feel of the image may be different even when the prints inherently look very similar.

Not all 1440 printers are alike. some are better, some lie, some use different ink configurations...these variables also come into play for making a better print. So to the color of the inks (which can vary), media, paper color, absorption/gain...

Then there is color management...

color correction...

capture equipment...

lighting...

and more.

The weakest link is where you can experience the most gain in final quality.

The easiest way to approach the variables is to look at the ultimate goal and be sure the cumulative parts can meet those requirements.

That help?
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Old 11-05-2003, 02:28 PM
Old Phogey Old Phogey is offline
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Thank you, yes, all this has helped. Your book approaches things from the 'bottom up' viewpoint which is right for me. The Tools seem to be what I need (Elements 2 came bundled with my camera, but some intial research made me think it wasn't much good for B&W - no channel separation, curves, duotones - but luckily I came upon your book and there it was!). Out of the fog of confusion, I'm beginning to see some clarity. And it looks like there's a bit of the old 'black art' in there. It's good to know there are people out there who are willing to spend some time helping starters such as me.
I now need to get stuck in to the practice. What am I trying to achieve? In the main, to be able to put up on my walls some good quality prints of a decent size, like I did years ago when I did my own B&W film developing and processing, + some printing in colour. My digital camera came as a retirement gift a couple of months ago. I had zero experience of digital photography before this. Hence my need to know what ancilliaries (e.g. printer) would be 'compatible' with my camera. It's in researching this I realised that this isn't so simple, and some of it is downright counter-intuitive.
I think I've learned a lot in the last few weeks, and realised there is a whole lot more to know. Just right for retirement!
BUT- I'm still not clear on the black and white printing aspect, and how this differs from colour. Will the same printer print, to a decent standard, both colour and black-and-white?
I suppose my 'decent standard' corresponds to 35mm 'slow' B&W film (exposed at around 25 to 50ASA), developed in fine grain developer, with good (well I thought so!) darkroom printing technique to around A4 size
Thanks again.
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