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12-17-2013, 03:17 PM   #16
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QuoteOriginally posted by stevebrot Quote
My printer supports pixel extrapolation (data is made up where data does not exist). I assume that is what you are using? Not a bad thing, it just depends on how close the viewer is to the print!


Steve
8 inches away you can see a difference, at 3 feet away, looking at a 30x20 print, it seems to be a mystery. As I said, there is some empirical evidence supported by tests on multiple subjects, that say from a normal viewing distance, 100 dpi and 300 DPI are pretty much indistinguishable. 300 DPI is probably pretty good for blowing your mind when you're stoned and 8 inches from the painting.

I'd love it if someone would do some definitive tests on this, but I doubt the printer companies would be happy.

12-17-2013, 03:46 PM   #17
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I just had a 30x20 print done at a printing service at 240 dpi (their recommendation) and it looks fine close up. Just to make it more confusing, inkjet printers use multiple dots of single colours to mimic each individual coloured dot in the digital image. Even if your image doesn't have enough dots to print clearly at the size you want, you can use software to upscale the image, and if the software does what is called "anti-aliasing", you will still get sharp edges in the print even if the number of pixels is much greater than what came out of your camera. Regardless if your camera produces 6 megapixel or 16 megapixel images, if the lens doesn't allow a sharp image to hit the sensor, you won't have a sharp print. At smaller print sizes, lousy images don't blatantly look as bad as they do at larger sizes, but you still can't make a silky 4x6 print out of that photographic sow.
12-17-2013, 03:50 PM   #18
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I'm sure you guys are all printing your own. But.

Unless you you are dealing with a custom processor (do they still exist?) anything you send to an online printing site will look about the same no matter what you send. They compress the the images you upload to a very small file before they print. Somewhere around here I have some tagged images where I tested various compressions and dpi counts.
12-17-2013, 03:53 PM   #19
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This thread might help as well: https://www.pentaxforums.com/forums/151-pentax-k-30-k-50/241835-large-prints-k-30-a.html

12-17-2013, 04:06 PM   #20
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@fevbusch, Am I understanding correctly that you aren't getting good 8x10 prints from your K100D files? 6 megapixels would give you around 250 dpi, and anything 200 or higher generally looks very good. Check whether your old K100D files were really saved at 6 mp rather than a lower resolution. Also check the settings in your processing software and printer; some printers have settings to make the most of "low resolutiuon" (below 300 dpi) images.

Viewers frequently won't notice anything wrong as low as 100 dpi unless they are "inspecting" the photo rather than "seeing" it. Photographers and artists are much fussier about dpi and image sharpness than the general public.
12-17-2013, 04:24 PM   #21
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QuoteOriginally posted by Colbyt Quote
They compress the the images you upload to a very small file before they print
The compression is done to save bandwidth and storage space at the server. It can be done by a script on the web page, or at the server. If the number of pixels in the image you upload is below what the printing service is set up to accept from the server, you will end up with a less detailed image than you are entitled to. To keep customer refunds to a minimum, the amount of compression shouldn't affect the final result to a noticeable degree, and you should almost always end up with as good of a print as the printer is capable of. I guess you could say the quality of the print is set to the expectations (or tolerances) of the kind of customers they are looking for.

QuoteOriginally posted by DeadJohn Quote
some printers have settings to make the most of "low resolutiuon" (below 300 dpi) images
If you operate the printer yourself, by all means experiment with these settings, but you can do the same with post-processing software and have more control over the final result.
12-17-2013, 04:24 PM   #22
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A lot depends on the picture being enlarged. Simpler shots with large expanses of the same thing, blue sky, yellow flower, etc. can usually be enlarged a bit more with lower dots per inch.

You can also use software like Genuine Fractals (no known as Perfect Resize) to get more out of your picture. I regularly use my ist DL2 (6 megapickels) to make 13x19 enlargements by using this software. However, it does not work as well with images that contain lots of detail.
12-17-2013, 04:26 PM   #23
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In my opinion, for prints larger than about 8x12, you are going to be fine with a 240 dpi or greater original. I make a point of sampling to the recommended printing resolution (300 for HP in my case). It is best to use a higher quality interpolation method - Lanczos at 6x6 or 8x8 is best; and you might want to apply conservative sharpening if upsampling. Not sure if the more-recent Adobe products have incorporated Lanczos yet. Bicubic and bilinear are not all that great (and fostered sampling programs like Genuine Fractals that provided some interpolation improvement).

12-17-2013, 04:33 PM   #24
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QuoteOriginally posted by Pioneer Quote
A lot depends on the picture being enlarged. Simpler shots with large expanses of the same thing, blue sky, yellow flower, etc. can usually be enlarged a bit more with lower dots per inch.

You can also use software like Genuine Fractals (no known as Perfect Resize) to get more out of your picture. I regularly use my ist DL2 (6 megapickels) to make 13x19 enlargements by using this software. However, it does not work as well with images that contain lots of detail.
Genuine Fractals can get pretty funky quickly with some images, as you say. I think it pretty much has been marginalized since Lanczos has become more widely available. It does a fine job of preventing jaggies as you upsample. Even Irfanview has it, but my use is through a more-comprehensive photo editing tool, Picture Window Pro. It takes a little more time, but separating the upsampling from any kind of sharpening is a cleaner operation yielding more exacting results.
12-17-2013, 05:44 PM   #25
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Something that always has to be considered is the intended viewing distance to the print. Let's Make two prints of the same subject using the same original image file. If you double the print size but also double the viewing distance, the print quality will look the same.
12-17-2013, 10:28 PM   #26
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QuoteOriginally posted by stevebrot Quote
it just depends on how close the viewer is to the print!
The late Bruce Fraser in his book Real World Image Sharpening published the chart below translating 20/20 vision to image viewing distance with eye resolution in DPI. This is about as authoritative as I've seen on the subject and should be useful in determining resolution requirements.



M
12-17-2013, 10:51 PM   #27
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QuoteOriginally posted by Miguel Quote
The late Bruce Fraser in his book Real World Image Sharpening published the chart below translating 20/20 vision to image viewing distance with eye resolution in DPI. This is about as authoritative as I've seen on the subject and should be useful in determining resolution requirements.



M
Very interesting. Here are two articles that I ran across about a year ago that include some useful equations that provide equivalent numbers to your chart:
Visual Acuity, DPI, and Resolution | The Creative Endeavors of

Visual Acuity, DPI, and Resolution – Revisited! | The Creative Endeavors of
The hitch is that people tend to walk up to a hanging photo and look at it closely as well as from a distance. So we had best to anticipate the close-focus limits of the youthful eye. 300 dpi is a liberal approximation of such.

Steve

Last edited by stevebrot; 12-17-2013 at 11:01 PM.
12-18-2013, 07:57 AM   #28
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QuoteOriginally posted by stevebrot Quote
Very interesting. Here are two articles that I ran across about a year ago that include some useful equations that provide equivalent numbers to your chart:
Visual Acuity, DPI, and Resolution | The Creative Endeavors of

Visual Acuity, DPI, and Resolution – Revisited! | The Creative Endeavors of
The hitch is that people tend to walk up to a hanging photo and look at it closely as well as from a distance. So we had best to anticipate the close-focus limits of the youthful eye. 300 dpi is a liberal approximation of such.

Steve
Very liberal…there are also people who have done test shooing people can tell the difference between 300 and 600 DPI up close. So you can definitely go over the deep end and the guy who has sold the world's most expensive photograph (Andreas Gursky) at over 3 million dollar clearly does, but he also shoots with two different lenses and overlays the images in some proprietary methods that give them a 3D looks, but the guy who only got a million for his image Peter Liks has an image that isn't dependent on resolution at all, but the more tradition, colour and pattern rendition. SO framing the discussion in terms of the limits of human eyesight is not necessarily a a good idea, unless you want to be Andreas Gursky. And you aren't going to be Andreas Gursky with a DSLR or even an MF camera, so just ditch that right now.

https://www.pentaxforums.com/forums/38-photographic-technique/203024-who-took...hotograph.html

You can go for the high def look, but it's not in any way necessary or in cases like Peter Liks photo, even desirable. And implying that you have to a produce an image where the viewer can walk right up to the image and see detail to the limits of the capabilities of his eyesight, is technogeeky. Folks like myself, who have consciously rejected cameras like the D800, because for our style, 36 Mp has little to offer over 16 Mp, because the added detail looks bad as often as it looks good, look at the Mp races and go pffft… I know pros who are still shooting 12 Mp and are doing quite well with it.

So there's a sliding scale there, that has to do with style and subject. And detail is just one of the factors that is influenced by style. If you really have to ask, "why wouldn't I just go for the most detail possible", talk to me when you've sold an image as good as Peter Liks. His image sold for a million, without jumping on the high def band wagon. It's sad, but to satisfy the detail freaks, you have to have a lot more than 36 mp. That's a tough market to work for.
12-18-2013, 09:06 AM   #29
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QuoteOriginally posted by normhead Quote
You can go for the high def look
Not really going for the high-def look...just want my prints to be acceptably sharp at reasonably anticipated viewing distances. No sense buying great glass if the results are not consistently present in the final product.

A recent example would be the calendars a photo friend of mine had printed and which she showed me a couple of nights ago. She is an excellent photographer and I was dismayed to see the poor print quality of reproduction on her calendars. The size was about 11x14 and did not reflect the state of her craft. What is the expected viewing distance for a calendar? Would it have been too much to ask for at least 300 dpi from the printers?

You are correct about there being a sliding scale. Much has to do with subject. Cartier-Bresson's work generally sucks from a technical perspective, but his subjects transcend the need for sharpness and technical perfection. On the other hand, would there be any merit in an Ansel Adams landscape if the print was less than technically superb?

Acceptable megapixels for large prints? In 2007, I heard a salesman pitching a Nikon D80 (10 megapixels) to a customer. In response to a question about maximum print size, the sales guy responded by saying that he had done acceptable 4x6 foot prints from images taken with that camera. Exaggeration to close the sale? Perhaps so, but if the print was displayed on the wall of a large corporate lobby, it may well have been acceptable. For the average suburban living room, it would have been less so.

As for "doing" Gursky with a dSLR or medium format...I have large format film for that.


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12-18-2013, 09:21 AM   #30
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QuoteOriginally posted by stevebrot Quote

As for "doing" Gursky with a dSLR or medium format...I have large format film for that.


Steve

Exactly, I think each of us at some point will make a decision, "will we go large format?" Having carried around an 8x10 view camera in my teens, and now being 65 years old, I think I'm pretty safe in saying, I could buy a large format system, but I probably wouldn't use it. I don't even use my MF film camera. On the other hand, I would encourage anyone one starting out to give Large Format a try. You can't really understand what it can do, until you work with it. I was envisioning a series the other night while lying in bed, how to do a series that would dramatically illustrate the advantages of tilt shift. I don't have a tilt shift system so I can't, but once you've worked with one, I think it's pretty safe to say, you realize that there a lot of situations where you'd improve your images if you had one with you. And if you haven't used one, you don't know what you're missing. It's not all about the resolution.
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