A question for the digital experts here

[tim atherton]

Jpgs also need to be in srgb color space. .

Okay - that's a new one on me...?

Chirs, what's the particular problem with using DVD's

[Scott Rosenberg]

Hmmm...viewing at 1600%, if there are no differences in color or contrast, I'd say you'll never see it in a print of any practical enlargement.

Limitations in the screen are present and consistent whether you are viewing at 1% or 1,000,000%. let's say you are trying to measure two lengths of pipe to see which one is closer to your target of 12.125 inches. if your ruler will only give you resolution to 1/10" of an inch, then your gauge will not be capable of returning a reliable result. you need a more precise instrument.

i was suggesting that in chris's case the resolution of the display might be inadequate to show differences in the file. however, a print, which has much greater fidelity than most monitors, may prove to be a more capable 'ruler'.

[Daniel Geiger]

I think the LZW compression should get you there easily, and with the least amount of worry.

If you are really concerned about quality, just burn that DVD. However, some DVDs I burnt on my G5 at home and sent to my stock agency, they had trouble opening. So cross-system/platform compatibility with DVDs is still a bit iffy [my experience so far]. Otherwise, think about a memory stick. The 1GB are not that expensive and re-usable.

For what it is worth, my stock agency now accepts (an soon will ONLY accept!) highest quality jpegs (no more tifs). This may be a question of "good enough", a debate that needs not be revisited. I still archive my files as tifs (on DVDs and a RAID5 array).

[Walter Calahan]

Chris

Save your master copy as a TIFF. Send Duggal Jpegs at #12 quality. As long as they are NOT opening and closing them a gazillion times before printing, you should see no difference. Just don't use the sRGB profile. Adobe 1998 RGB is standard for printing.

Never trust you monitor!

Personally I'd send a DVD, they are not that expensive compared to a regular CD, just your computer system can't burn DVDs.

[Ken Lee]

The differences you see, depend on the nature of the image.

JPG compression replaces adjacent tones of the similar shade, with larger square "tiles". Greater compression means that the algorithm is more tolerant when it comes to chosing an adjacent tone that is almost the same color - so there are fewer, larger tiles. This, as Ted has pointed out, it is a lossful method. Once the similar shades have been tossed out, they cannot be retrieved.

When your original contains large uniform areas (for example a grey sky), such areas can be replaced by a small number of tiles, with little visible impact. On the other hand, if your image contains a lot of small details (such as a sandy beach in strongly angular light) then the replacement will be more obvious, and it will be very easy to distinguish between lossless and lossful compression.

[Ken Lee]

Photoshop has its own lossless compression algorithm. It is not universal, but due to the popularity of PS, it might as well be.

Although non-Mac web browsers can't handle them, you should attach an ICC profile to your original, so that you preserve the color space in which the image is to be viewed. On a calibrated system, this will guarantee that others will see what you intended.

Does anyone know if the new Internet Explorer 7 supports embedded ICC color profiles ?

[Jack Flesher]

Chris, there are several not readily apparent issues to consider...

1) jpegs by default are 8-bit and should be in the sRGB colorspace. sRGB is a very small colorspace and using a larger colorspace can cause banding in even-toned areas of the image

2) you did not see a difference between your jpeg and tiff images because your monitor is also essentially an sRGB colorspace device and cannot effectively display colors outside sRGB.

3) If you instead get the print profile from your lab, then compare the images in CS using CS's "soft-proof" engine, you will likely see a difference, but

4) Unfortunately it takes a trained eye to understand how the relatively minor soft proof differences that show on your monitor translate to significantly larger differences in the print

5) Most all current printers are capable of printing colors far outside the sRGB colorspace, so you will indeed lose some of the available color if you use jpeg sRGB

6) A 16-bit tiff allows a lot of room for your lab to "adjust" and convert your original image to their working colorspace without deteriorating your original image; an 8-bit sRGB jpeg allows essentially none.

7) My .02: In conclusion, if these are good quality, fine art images, you would be well advised to swallow the slight additional cost of burning your tiffs to DVDs and sending your lab the ultimate print file you can send


Cheers,

[chris jordan]

With 12-quality JPEG's I can see no tiling, and it is easy to embed a colorspace other than sRGB so the images stay in the proper colorspace. But the files come out so much smaller that it's hard to believe they aren't compromised in some way.

[Scott Rosenberg]

With 12-quality JPEG's I can see no tiling, and it is easy to embed a colorspace other than sRGB so the images stay in the proper colorspace. But the files come out so much smaller that it's hard to believe they aren't compromised in some way.

chris, you can only see what your monitor is capable of displaying. making a few prints might bring into relief subtleties lost on your display.

Let’s say you and I both hit a golf ball, yours went 325 yards, mine went 305 yards. If our judge could only see a distance of 250 yards, would he be able to tell who drove the ball farther? The differences in the files might be outside of the capability of your display. Just because you don’t see them, doesn’t mean they aren’t there.

[Jack Flesher]

With 12-quality JPEG's I can see no tiling, and it is easy to embed a colorspace other than sRGB so the images stay in the proper colorspace. But the files come out so much smaller that it's hard to believe they aren't compromised in some way.

That's because they are compromised -- a quality 12 jpeg is still compressed and jpeg compression is lossy...