This question came up in the forum this morning, and I wanted to address it here. What you’re reading below is my response to the question; “is it worth scanning my negatives to TIF for manipulating in Aperture, or should I just scan to JPG”? JPEG files are of course a lot smaller then TIF, so for anyone scanning a large library of negatives, this is a pretty important question.

Here is my response. As you’ll see, there are gaps in my knowledge when it comes to scanners, and if you, dear reader, have any additional information, feedback or corrections, please join the conversation in the forum. I’ve closed comments here; I’d like any discussion to happen on the original forum post. Thanks.

TIF vs JPG for scanned negatives

The essential advantage of TIF is twofold; one, it’s uncompressed, and two, it can be higher bit-depth than a JPG. JPEGs can only be 8-bit, whereas a TIF can be saved up to 16-bit (the spec actually allows for 24-bit RGB or 32-bit CMYK).

If you were scanning from prints, I don’t believe there’d be any advantage to scanning at a higher bit-depth into TIF. But since you’re scanning negatives, if your scanner is very high quality and can scan at higher bit depths, then yes, a TIF (saved at that higher bit-depth) would be effectively retaining more of the original information.

CAVEAT: What I know about scanners you could fit on the head of a pin. So what I just said above, while theoretically correct, may in all practical terms be absolute bollocks. If a scanner of any caliber is incapable of scanning at higher than 8-bit depth, or if it’s incapable of extracting that super-fine color detail that merits a higher bit depth, then saving to a higher than 8-bit TIF is pointless. I simply don’t know what scanners today are capable of. So again, if a scanner can truly scan at higher than 8-bit depth, then by all means, saving as a high-bit TIF would give you more data. Think of it like a RAW file almost. A RAW file is more than 8-bits, and it’s only when you render it to screen that you have to reduce it to 8-bit depth. The raw data is all there; you get to manipulate it however you like to pull it into view on screen. This is the difference of shooting JPG, of course… if you shoot JPG, all you’re saving is 8-bits of data, and throwing away everything else that the sensor captured. More on accessing that higher-than-8-bit data at the end.

As far as uncompressed TIF vs compressed JPG (removing the bit-depth discussion), a quality-10 JPG is virtually indistinguishable from a TIF. Unless these are the most important images of your life, I’d say a full-quality JPG is absolutely sufficient. Also I was advised once that if you see higher than 10 quality option, i.e. quality 12, that it is not any different than 10 and just takes more space. I have a hard time believing this on molecular level, but it’s easy enough to test the different for your setup—more on that in a moment.

So in short, if you aren’t getting higher than 8-bits from your scanner, and you aren’t archiving the most important images in the (your) world, then I’d just go JPG.

Comparing TIF to JPG

How do you compare qualities? Using Photoshop it’s easy. Scan a file at the highest quality setting your scanner can muster, and then save out multiple files from the same scan. Save a TIF, a quality 12 JPG if it’ll do it, and a quality 10 JPG, and just for fun, do a quality 8 as well.

Open all the files in Photoshop, and stack them as layers in one file. Make the TIF the bottom, since that’s the “baseline” file. Save this stacked file so you can easily revert to it.

Turn off (hide) all JPG layers except the quality 8. Set the mode to “difference”. You will see an all-black image. If there’s any difference between the original and the JPG, you’ll see it here in the form of colored pixels or artifacts (to see the effect in action, nudge the JPG layer one pixel and you’ll see the offset immediately. Now put it back). With the 8-quality JPG, you might see some of this color “difference” right away. But to really see it, do this:

Flatten the file (discard the other layers; you will revert to get them back). Now hit the Auto Levels command (shift-command-L I think?) The faintest speck of color will now be raised to full brightness, and the differences between the files will leap off the screen. Do it again… hit Auto Levels again and again, and you’ll see it get more and more obvious. THAT is the difference between the TIF and the quality-8 JPG.

Now that you understand that quality-8 sucks, revert the file and repeat the test with the quality-10 JPG. Can you see any difference after the first auto-levels? Chances are if there’s anything, it’ll be really, really minor. Can you live with that? Probably. If not, try quality 12, but again I doubt you’ll see much — if any — difference showing up at all.

More about bit-depth in Aperture

Let me talk a moment about the working bit-depth. Aperture is working non-destructively, as you know. And what you see on screen is only 8-bit, because that’s all that our screens can display. However the mathematical calculations that are happening to modify your image are being run in floating-point bit depth, which is to say, from my limited understanding of the topic (and here I really may be showing how little I know), you’re working in a virtually unlimited color space (or perhaps it’s 32-bit… which is still, you know, a lot). So if you are opening a RAW, 16-bit or 12-bit TIF file, you are opening all that data into Aperture’s floating-point bit depth to work on. You can then pull data down into the visible 8-bit space to show on screen (this is where the extended Curves view comes in handy, where you can see data beyond the 8-bit space in the Curves’ histogram). So if you do have a 16-bit TIF that actually does have more than 8-bits of data, then yes by all means, Aperture will read that and give it to you to manipulate.

What do you think?

If you have anything to add (or correct!), please join the conversation in the forum. Comments here are closed.