how big can you blow up...
 

Just wonder what size these digital photos would print at naturaly, and what size they can be blown up to while still achieving acceptable quality?
640x480
1600x1200
3072x2048

Thanks

I've printed my 1600x1400 photos from my camera up to about
letter/A4 size without it looking bad (in my eye)... But then again
I'm not really into still stuff, so...

I print my 6M shots from my Canon 10D at 13 x 19 and get results that are indistinguishable from (and even surpass) the chemical film & paper 16 x 20 prints I used to produce in my color darkroom (until I sold it and bought a good digital photo printer ;) ). Examining the grain pattern with a loupe, I don't think it would be practical to go much larger than 13 x 19. However, there are programs that will extrapolate intermediate pixels that, at least as I've been told, allow producing poster-size or better.

As a follow up, and in response to the first part of your original question, there is no native size for a give resolution -- everything depends on the dots-per-inch you select for your printer. The usual rule of thumb for producing photo-quality digital prints is to use 200-300 dpi (I usually prefer 240 dpi, though I know of folks who use 225 dpi). At 240 dpi, you'd get the following print sizes:

640 x 480 = 307K = 2.6" x 2"
1600 x 1200 = 1.9M = 6.6" x 5"
3072 x 2048 = 6.3M (Canon 10D resolution) = 12.8" x 8.5" (roughly A4)

Perfect answer!

Thanks Paul!

Just to keep matters clear, image files use ppi (pixels per inch) and printers use dpi (dots per inch). Some argue that files that go to the printer should be at a multiple of the printers resolution. For example if a printer prints at 1440 dpi then the files sent to it should be 240 ppi, 360 ppi, 480 ppi, or 720 ppi.

Increasing the ppi through interpolation doesn't create new data and the image files can get huge. I use an Epson 2200 and send files to it at 360 ppi. The printer resolution is set to 1440 dpi unless I'm going to 13x19. If I'm printing 13x19 some images seem to benefit from printing at 2880 dpi. The disadvantage of printing everything at 2880 is increased ink consumption and slower print times.

For what it's worth, you can get an 8x10 from a two-megapixel image (1600 x 1200). It's definitely pushing the limits, but it's possible, although a bit of softness will be present in the print. I've got a Canon print sample book with a number of two-megapixel 8x10's which look great, as long as you don't put a four-megapixel print next to 'em.

I work at an organization where we frequently create several glossy magazines, comparable in quality to what you see on the newsstand. Often there is need for product shots and such for ancillary stories, and I'm usually asked to take those shots. Over time, we've come to realize, that in the magazine world, you don't want to go below the 3MP range if you want a full page photo (letter size).

But what's also important is that it's more about the quality of the camera than MP size. I've used 4MP cameras that just don't look all that good. I've found Canons to be my favorite for this application. I have, however, never used a Nikon digicam. I've found several Sonys to be good too, but they need to be color corrected more than the Canons.

The difference is in the camera's image processor. While the megapixel rating primarily determines the maximum print output size, the actual quality of the image depends on the processor. Canon's CPU is proprietary technology, built from the ground up as a photography-specific chip. All others are off-the-shelf electronics components that can be found in PlayStations, Gameboys, X-Boxes, etc. Although Nikon does look very, very good.

Thanks guys!

Out of curiosity, how big can you blow up 35mm film?

I'd say sky's the limit with that. I mean, unlike digital shots, when you blow up 35mm, the worst that happens is that it gets fuzzy edges, not nasty pixelated edges. Plus the larger you get, the less important resolution really gets. Like billboards - those things are printed at something like 100dpi, but it's not like you look at them up close.

Plus, they do, after all, project 35mm film at billboard sizes every time you go to your local theater.

Ultimately, the most important thing is that at blown up sizes, film just starts to look soft. But it's very tolerable. Digital shots that are blown up past their recommended size just look nasty.

I've blown up unexceptional 35mm prints up to movie poster size before, with no complaints. Imagine what you can do with well shot slide film...

ive seen a post size print of the Digital Rebel's image (basically the exact same image as the 10D) and the image looked AWESOME! hardly any grain at all! so much information...

you could try a program called "Genuine Fractals." It does an awesome job of blowing up images with awesome results...

We have a large format printer here at The Media Union. It's a Hewlitt
Packard and is about 4 years old. It can only print at 75 DPI.
I have printed out some 10D stills 3 feet by 4 feet. Although
their quality is not stupendous compared to what the newer
printers can accomplish, most people are awed by them.

The 10D is amazing and if Canon can get this kind of quality and resolution
in the XL2 I will be the first to open my wallet.

Film is limited by grain. In most cases a print larger than 16x20 will not appear acceptably sharp. Digital images lack noise (grain) and are not limited in size by grain. Digital images, however, will show a lack of resolution that limits the maximum size of the digital image.

There are techniques for both film and digital that allow larger size prints to be made with minimal grain or sufficient resolution. A 4x5 interneg can be used with film to help reduce grain. Specialty software can be used to enlarge digital files.

Several digital cameras produce files that equal or exceed 35mm film. Viewing distance is of great importance. Billboards look sharp because you're viewing them from extreme distances (hundreds of yards in most cases).

Jeff,
I had a question that you could probably help me with. In developing a negative (35mm), would developing to scan and to print traditionally be the same? Or would a developer suited for printing on an enlarger not necessarily be good for a negative intended to be scanned and printed? Thank you for your help.

matt

Traditional C-41 processing (color negative) is designed to yield a properly developed negative for traditional color printing. This process is optimized for the traditional output, archival color negative and a RA-4 processed color print.

Until recently there wasn't much choice. However, a company was recently perfecting a process whereby the film is processed in dry chemicals (non-wet process) and scanned at intermediate steps of development. Thus the maximum amount of information was obtained in the shadows and highlights. The dynamic range was very high. The last I heard was Kodak bought the company and was continuing development of the process. I haven't heard any further progress in the last year and I'm afraid Kodak may have shelved the program.

So if I want to scan a 35mm transperency to create an A4 (8.5x11.5) print on a 2880x2880 printer what res should i be scanning at?

That's a shame. I could see that being very attractive, especially if the process could work with one's film scanner they already own and maybe a new program to capture and combine all the scans. I think if anyone could see it through it would be Kodak, but I keep reading that they're making big cuts in their film department and pretty much focusing on digital. Kind of a shame, but then again theres always Ilford. Thank you.

matt

Most scanning software will give yo several different options to adjust the scans file size. You can adjust the target size to anything from original (24mm x 36mm) to finish (A4). Adjust the ppi of the scan to your desired resolution. I like to print files with 360 ppi. So, for the A4 print I would scan at 3060 ppi if keeping the target the same size. If you adjust the target size to A4 then scan at 360 ppi. Some people will print as 200 ppi if the finished size is very large and the viewing distance is also very large. I prefer to print at multiples of the printers native dpi, 360, 240, 480, 720. The greater the ppi the larger the file size.

Thanks Jeff, I've got it now. The ScanGear utility that come with Canon scanners uses output resolution and target image size. Everyone was saying scan at 3200 and if I did I was getting 300+ MB files sizes which was killing my nearly 4 yo PIII.