best non-lossy graphics file-format?

John Pelz · Post by **John Pelz** » 16 Nov 2004 4:58 pm

I want to get some late 1950s-era 35mm slides of my mom & late father transferred to CD-ROM & then fiddle with the images a bit & print them up for my mom for Christmas. (Don't tell! She doesn't hang out at the Steel Guitar Forum anyway, so I don't think she's going to find out...

I'm thinking of using a local video production company to do the transfer. If I do, I will need to indicate to which graphics file-format I want the slides transferred.

I really don't know much about the strengths & weaknesses of all the different computer graphics file-formats, and was wondering if anyone can advise me on what would be the best file-format to use, and which would provide an archival-quality digital image?

I do know enough (or at least I think -- and hope -- I do!) to avoid JPEG, as that is a lossy format. File compression is not an option for me. I don't care if the resulting file-size is gigantic -- I just want to use the best non-lossy format. Should I use TIFF? BMP? Something else?

Thanks in advance for any help/advice.

Jon Jaffe · Post by **Jon Jaffe** » 16 Nov 2004 6:33 pm

John,

The input file to a printer is not important if the output is not equal to or better. You wouldn't play your steel through a Pignose. TIFF files are fine, but remember you are scanning from a small slide. Will you use Photoshop® to manipulate the files, and How big will you print them? Will you give your mom a copy of the files. If the input is good, ie the scanning was done well, then I do not believe you would notice the difference between JPEG and TIFF files on the average home printer. Any good image manipulation program should work with ALL files.

Jon

Andy Volk · Post by **Andy Volk** » 16 Nov 2004 6:43 pm

John, you want to use .tif or PDF. JPEG is a compressed format that recompresses the image each time you open it. TIF is an uncompressed format. PDF saves the image as vector data.

John Pelz · Post by **John Pelz** » 17 Nov 2004 7:09 am

Thanks for your response, Jon. Your analogy/point about playing my steel thru a Pignose is well-taken, and is something that hadn't ocurred to me. Hmmm, that's some food for thought. I'd be using Paint Shop Pro 7 to do any manipulating, and was planning to make 4X6 and 5X7 prints. If I decide to manipulate the images any, I was thinking of taking a disc of the resulting transfers to the local CVS store, where they have one of those do-it-yourself digital print kiosks. I seem to get better results (print-wise) with them than I do with my own computer. Any transers that needn't be fiddled with, I suppose I'll just have the video production co. print up themselves, as they do have photo services. (They specialize in wedding photos.)

Thanks for the info, Andy. Sounds like TIFF may be the way to go. Also sounds like I need to do some more research about graphics file-formats online! Your responses have given me a good starting point. The bottom line is just that, without particularly knowing just what the heck I'm talking about here, I want to avoid any file-format that may affect image quality thru simple use of that format. I might be sweating the small stuff here and won't notice any visible differences between the file-type I use, but these are 35mm slides from the 1950s, and which have a lot of sentimental value to my family & me. I just want the best format for slides that may be blown up to prints as large as 5X7. Sounds like TIFF will work; I'll read up a bit more on graphics file-formats, too. Thanks very much for the helpful responses.

Brad Sarno · Post by **Brad Sarno** » 17 Nov 2004 11:13 am

We had some prints professionally photographed for digital reprinting. The files are about 25megs each and the guy saved them as TIFF files.

Brad Sarno

Will Holtz · Post by **Will Holtz** » 17 Nov 2004 11:43 am

A few clarifications are in order. PDF files save line art as vector data, and thus are lossless for line art. However, PDFs usually downsample bitmap (photo image) data, thus reducing the resolution to something comparable to your output resolution.

TIFF is always a lossless format. There are compressed (LZW) and non-compressed versions of TIFF. TIFF is quite common in the desktop publishing and stock photography worlds. I would recommend using compressed TIFFs if you want the best image quality and a high level of compatibility.

JPG files have an adjustable level of loss in their compression. If you set them to a low level of loss, you probably will have a hard time telling them from the originals and they will be much smaller. This is fine for almost all non-professional uses.

PNG is an up-and-coming lossless graphics format that has some advantages over TIFF, however until it catches on more, there is a trade of with compatibility with existing applications.

Jon Jaffe · Post by **Jon Jaffe** » 17 Nov 2004 12:44 pm

Ok, now that I have made some sense, lets forget about file types. I feel that input and output quality are the key. It is akin to your right and left hand technique. Good technique will sound well whether it is transfered with an old coiled guitar cord and pot pedal or the best of electronics. The major loss is the input and final output, not the transfer media. So lets talk about pixels and dots. If your 35mm slides are scanned at a very high density, say 4200 pixels per inch and are printed at 600 ppi and 4in by 6in, where do the extra pixels, or dots, go?They are lost, they are not printed. You may have noticed that high density images appear very large on your monitor that displays at 72ppi. Nothing is lost, so the image is real big. Digest this and we can talk about manipulating large files v. average size files with the softare and computer power you have

Jon Jaffe · Post by **Jon Jaffe** » 17 Nov 2004 1:19 pm

My suggestion is to have the slides scanned at the highest resolution you can. Store these for archival purposes. Next convert (scale) them to a lower "resolution" with your software. Manipulate and print the smaller images. Printing a 35mm slide to 8x10 involves loss even with direct printing and I suspect you will opt for a smaller size. Keep in mind that any of the work that you do to the files will be lost when sent to the pharmacy, as they batch everything. I would beg borrow, steal or rent a dye sublimation printer (<$200 for a Canon), and spend the time tweaking and printing them your self. If it is a custom photo place (not Drug Store) that is scanning, then they will work with you on printing. I scan my old slides and negatives frequently. If I am working with big high density images and a >$10,000 printer then JPEG or TIFF makes a difference. However, most of the time it just doesn't matter. Good input + good output.

Cal Sharp · Post by **Cal Sharp** » 17 Nov 2004 2:12 pm

Well, let me stir the pot a little more. Pixels and DPI have always been confusing to me, so I just made a little test. I scanned a 35mm slide twice, once at 1200 DPI and 100%. Then again at 300 DPI at 300%. I saved them as tifs and put them in InDesign, made them the same size, and printed them on photo paper. There was virtually no difference. However, as you can see from this screen shot, there is a noticeable difference when you zoom way in. The one on the bottom is the 1200. www.calsharp.com/music/Scans.htm
If I had printed them both out at 8x10 there probably would have been a difference.
The 1200 DPI file size was twice as much as the other one.

C#[This message was edited by Cal Sharp on 17 November 2004 at 02:13 PM.]

Jon Jaffe · Post by **Jon Jaffe** » 17 Nov 2004 2:27 pm

Hoorah. At Last another MacAholic. I agree, however your output is to a 72 DPI screen, and not a printer. As long as the file has a size that is greater than the output of the printer considering its dpi and scalled to the size of the printer output then all will look well.

Jim Peters · Post by **Jim Peters** » 17 Nov 2004 2:33 pm

Save them all as tiffs. Later on you can always fool around with them and save as jpegs, but you can always get the original tiff and start over. Anytime you manipulate a jpeg and save it, you lose a little information. Once you save as a tiff, burn them to a cd for backup, I learned that one the hard way!JimP

Bobby Lee · Post by **Bobby Lee** » 17 Nov 2004 4:34 pm

For color photographic prints, your resolution does not need to be greater than half of the resolution of the printer. For example, if the printer is 300 dpi, anything above an image resolution of 150 dpi is wasted.

The reason is this: a single dot on the paper cannot represent the full gamut of colors. Printer drivers use a technique called dithering to average adjacent dots of different hues. The eye averages the color of several dots, and the result is accurate color presentation. Any resolution that maps to less than 2x2 printer dots will have a near-zero effect on image quality.

We actually did studies on this at Broderbund. Even with 1200 dpi color laser printers, people who could see a difference in photo quality at above 200 dpi were rare.

So, if your target is a 4x6 inch print, you should scan to a 800x1200 pixel image, max. Anything higher than that is wasted.

The various lossless file formats have different pixel depths. Be sure to specify that you want "true color" at "24 bits per pixel". Once you've specified 24 bit color, there is no difference in image quality between TIFF, BMP, TGA, PNG and "lossless JPEG" (yes, there is such a thing).

TIFF can be compressed or uncompressed, which makes a big difference in the size of the file on disk. A lot of programs don't support compressed TIFF because it's hard to decode, and the patented decoder algorithm required a license until just recently.

PNG is always compressed. 24-bit PNG is my preference for lossless images these days. Most of the newer programs support it. PNG files are usually smaller than compressed TIFF files of the same image.

------------------
<img align=right src="http://b0b.com/Hotb0b.gif" width="96 height="96">Bobby Lee - email: quasar@b0b.com - gigs - CDs, Open Hearts
Sierra SD-12 (Ext E9), Williams D-12 Crossover, Sierra S-12 (F Diatonic)
Sierra Laptop 8 (E6add9), Fender Stringmaster (E13, C6, A6)[This message was edited by Bobby Lee on 17 November 2004 at 04:36 PM.]

Will Holtz · Post by **Will Holtz** » 17 Nov 2004 4:37 pm

To work through your example, if you scan the 35mm negative (1x1.5 inches) at 4200 DPI, you will get 26.46 million pixels (1*4200*1.5*4200). Printing a 4x6" at 600 DPI uses 8.64 million pixels (4*600*6*600).

The extra pixels don't exactly get thrown out, but several of the initial pixels get averaged together to make up one pixel in the output.

When there is no resampling, the math works out like this:
shortSideOut=(DPIin^2*shortSideIn^2*AR/(DPIout^2*AR))^0.5
where DPIin is the input resolution
DPIout is the output resolution
shortSideIn is the smaller dimension of the initial image (1" for the negative example)
shortSideOut is the smaller dimension of the output image (4" for your example)
AR is the aspect ratio (long side divided by short side = 1.5)

Thus a 35mm slide scanned at 4200 DPI has the same number of pixels as a 7x10.5" 600 DPI print.

I hope that is helpfull.

John Pelz · Post by **John Pelz** » 17 Nov 2004 6:35 pm

Wow -- a lot of this is way over my head and my immediate concerns, but thought-provoking reading nonetheless. Interesting thread! (If I may say so myself...)

Cal Sharp · Post by **Cal Sharp** » 17 Nov 2004 7:44 pm

Thanks for the input, guys. What I was trying to do was figure out how to scan a slide and get the same printed quality as when I scan a larger photo. I found that I get a picture with the same number of pixels when I scan at 100% and 600ppi (pixels per inch) that I get at 200% and 300ppi. (I think those were the numbers - it's been dozens of scans ago.) So then I scanned a slide at 300ppi and set the target size for 8x10. I then scanned a 4x6 photo at 300ppi and set the target size the same. Both pictures were about 3000 pixels wide (landscape). So it seems that it's the percentage setting rather than the ppi setting that will give me what I'm looking for, and I don't have to do any math.

>

C#

Bobby Lee · Post by **Bobby Lee** » 18 Nov 2004 3:04 pm

Yeah, 3000 pixels wide is overkill unless you're planning to zoom in on a selected area before you print. For an 8"x10" print, 2000 pixels wide (landscape) is plenty, and 1500 is probably enough.

Remember that it's not just disk space that you have to worry about. The application that does the printing has to hold the whole picture in memory. It takes 3 or 4 bytes per pixel (depending on the application), so a 3000x4000 image can easily consume 48 MB of RAM. All of that has to be sent to the printer, which can take a long time. If you can get the same results in 1/4 the time, why carry around all that extra pixel weight?

I think that the industry has gone mega-pixel mad. They're selling these devices without considering the load that their huge data put on the typical home computer. I never set my camera above 1024x768.

------------------
<img align=right src="http://b0b.com/Hotb0b.gif" width="96 height="96">Bobby Lee - email: quasar@b0b.com - gigs - CDs, Open Hearts
Sierra SD-12 (Ext E9), Williams D-12 Crossover, Sierra S-12 (F Diatonic)
Sierra Laptop 8 (E6add9), Fender Stringmaster (E13, C6, A6)

Cal Sharp · Post by **Cal Sharp** » 18 Nov 2004 5:43 pm

1024x768? That's just the medium setting on my 1.3MP PowerShot A10. I thought I needed a new camera.

Jeff Agnew · Post by **Jeff Agnew** » 19 Nov 2004 4:29 am

Cal,

This article, Understanding Resolution, may help explain things better. The only difference from your situation is that they're referring to a camera-made image instead of one from a scanner.

The important point to grasp is that a digital image (scanned or photographed) has no absolute size or resolution.

Cal Sharp · Post by **Cal Sharp** » 19 Nov 2004 6:32 am

Great link, Jeff. I get it now.

Jim Peters · Post by **Jim Peters** » 19 Nov 2004 9:12 am

A lot depends on how much you cropn a picture. If you start out with 1 million pixels, and crop 1/4 of it out, you lose 250,000 pieces of information. That is why an optical zoom is so important on digital cameras. I have only a 2.1 Fuji camera, but it has a 6X optical zoom. If I zoom a closeup portrait of the grandaughters, I can easily print a 8X11 picture. But if I don't optically zoom for the closeup, and have to crop 1/2 the picture, I can only print a 5X7. JP

Roger Kelly · Post by **Roger Kelly** » 19 Nov 2004 9:24 am

Great topic....you guys have answered some of the questions that I have been wondering about for a long time.

Cal Sharp · Post by **Cal Sharp** » 19 Nov 2004 2:03 pm

OK, here's what I learned today: The optimum dpi/ppi for desktop printing is somewhere between 240 and 360. I opened two pictures in Photoshop, one taken with a 6.3MP camera and one taken with my 1.3MP camera, both at 180ppi. With no resampling, the one from the 6.3 would print a 5x7 at 438ppi, and the other at 180ppi. The bigger picture can be downsampled to lose the extra file size, but upsampling the smaller one would result in some loss of quality. BTW, Canon has a new 16.7MP camera for a mere 8 grand.