Conversion File Size should be...?

<p>Hi Everyone,<br>

I use LightRoom 4 to convert my files from RAW to JPEG for webbase viewing only thus far, but I really need your help what size should I save my pictures from conversion should I need to print them for, say 16x24, prints? Your help is much appreciated. Thanks!!</p>

<p>why do you need to 'save' them? Just print from LR to the desired size and DPI and it'll do the uprezzing for you if required.</p>

<p>For clients that would want to print them. I don't sell by prints.</p>

<p>For a 16" x24" print, I would always send full-resolution image files. That is, I shoot with a couple of 24MP cameras. So straight from the camera my images are 4000 high x 6000 pixels wide (in landscape). If I didn't crop the photo, I'd send that res: 4000 x 6000. If I did crop the picture, well, of course, I'd send whatever I had after the crop.</p>

<p>To be honest, I upload high-res (full-res) photos to my service for <em>any</em> prints, even 4" x 6". I only do this for images of which the client orders prints, but I find it easier simply to upload the big file and leave it at that. That way the client can order two 4" x 6" prints and one 8" x 10" and maybe something else — and I don't have to do any math.</p>

<p>The math however isn't difficult. What is your desired dots-per-inch resolution? Let's say it's 300 dpi (nice high-resolution print). At 300 dpi, to print a 4" x 6" print, you'd ideally want <br>

4" * 300 pixel --> 1200 pixels on the short size<br>

6" * 300 pixels --> 1800 pixels on the long side<br>

So for a 4" x 6" print, good quality, you'd want an image that was 1200 x 1800 pixels in size.</p>

<p>HOWEVER, print resolutions vary. 300 dpi is overkill for many prints. Satisfactory prints can be made as much lower resolutions. For certain really high-end printers, 300 dpi isn't enough. And while, in theory, a 24 MP 4000x6000 pixel file can<em> "only"</em> be printed up to 20" x 30" (at least at 300 dpi), the fact is, I've made really nice very large prints with even lower-res images.</p>

<p>If you're planning to print yourself, you will want to spend a lot more time looking into these matters. But if you're planning to upload your images to a lab's site and place an order, then by far the easiest thing is to forget about the math and just upload the highest res file you've got. </p>

<p>Good luck and I hope your prints come out great.</p>

<p>Will</p>

<p>•<br>

V.I.P ("Very Important Postscript"): Above, I was talking about image size (in pixels) and print resolution (in dots-per-inch or DPI). I did not mention JPEG "quality." That's because the "quality" option when you're exporting, say, from Lightroom or Aperture, doesn't affect the pixel size of your images. It affects only the <em>compression </em>applied to the JPEG file.</p>

<p>Exporting at highest "quality provides no compression and thus your JPEG file will be maximum file size. But a little bit lower "quality" setting may reduce the file size considerably without appreciably diminishing the print quality of the file.</p>

<p>For example, I just did a test with a raw file that was originally 4000x6000 but which has been cropped down to 2314x3240 — roughly the pixel res of an 8 MP camera. Now, when I export this image from Aperture using the original size option and the highest "image quality" setting (12 out of 12), I get a resulting JPEG on my desktop that's about 9 Megabytes in size. If I go back and export the same image again, once again at full size but lower the "image quality" setting to 9 (on a scale of 12), the resulting image is only 2.4 MB. That's quite a difference in file size or "weight" and of course a 2.4 MB file is going to upload a lot faster than a 9 MB file. But there is <em>virtually no difference in the images </em>that is going to matter to making a print. </p>

<p>Anyway, I <em>never</em> export my images at the highest image quality. Simply dropping the "image quality" in Aperture (for this image) from 12 to 11 causes the output file's size to drop to 3.3 MB. I don't know that you'd be able to tell the difference between that IQ=11 file from the IQ=12 file even if you compared them pixel by pixel.</p>

<p>This is just an example, and the file-size reduction you get by lowering the image quality 1 notch will vary from image to image. But a small reduction in image quality (in other words, turning JPEG compression on at the most basic level) almost always results in a significant reduction in output file size. So I almost always export at 11, rather than 12.</p>

<p>Jeff Friedl did a great analysis/comparison of differing jpeg quality settings vs. file size on his website (regex.info)</p>

<p>Thanks Howard!</p>

<p>Thank you also for your input, W. Porter!</p>

<p>Ethan, I just saw your follow-up post. Howard M. asked why you wanted to save your files (a good question, in retrospect) and you replied:</p>

<blockquote>

<p>"For clients that would want to print them. I don't sell by prints."</p>

</blockquote>

<p> <br>

Ah, well, that slightly changes my reply. Doesn't change the technical part of my reply. But you see, when I'm uploading files to my lab's servers, I'm not worrying about what size prints will be made, and I'm also not worried about the lab having full-res copies of my images. I trust the lab.<br>

<br>

Reading between the lines here (the very few lines you've provided), I'm guessing that your problem is, <em>The client has asked for image files with high-enough resolution that he can print them, but you don't want to give him the full-res files.</em><em> So you're trying to figure out how to compromise here between his wish to print and your interest in keeping the highest res files to yourself. </em>I mean, if you're <em>not</em> trying to protect yourself in some way, then why not just give the guy the highest res file you've got an let <em>him</em> figure it out from there?<br>

<br>

Now, if I'm phrasing the problem correctly, I can offer two alternative responses.<br>

<br>

First answer: You could come up with some value that is <em>less than full res but high enough. </em>For me, with my 24 MP original files, that would be a 50% resizing (down to 2000 x 3000 pixels). An image that size <em>can</em> be printed, and probably printed pretty nicely, at 8" x 10", 8" x 12", even 16" x 24". But 16" x 24" is a pretty big print, these days especially. If you're just giving him <em>one</em> file, then do the math at 300 dpi:<br>

16" x 300 dpi = 4800 pixels<br>

24" x 300 dpi = 7200 pixels<br>

So give him an image that size, if you have one. But you probably don't. So your choice is either (a) assume he's going to print at a lower dpi, say, 200 dpi, and redo the math (200 dpi comes out to 3200x4800 px), or (b) forget about math, give him the full-res file and be done with it.</p>

<p>Which leads me to my second and more serious response: Just give your client the full-res files. This makes life simpler for you. And you aren't saving them to sell prints yourself, so why wouldn't you give away the full-res files? In this case, you don't have to do any math. I do NOT give clients full res files, because I want to make money from print sales and even more because I want to control the quality of the prints that they get.</p>

<p>Will</p>

<p>Howard, </p>

<p>Thanks for mentioning the article on Jeffrey Friedl's site, which I hadn't seen before. I assume you're talking about <a href="http://regex.info/blog/lightroom-goodies/jpeg-quality">this article</a> and not his other article about NEF compression. </p>

<p>Will</p>

<p>Yes, that is the article I was thinking of. The NEF article is also quite interesting :)</p>

<p>Well, the article by Jeffrey Friedl that Howard mentioned makes a counter-intuitive and surprising point: aggressively compressing an image with not much fine detail and large areas of similar but not identical tonality may actually hurt that image <em>more </em>than aggressively compressing an image of a million people in Tiananmen Square. Exactly the opposite of what I thought was the case. See Friedl's comparison of his blue sky with sea gull vs his pic of the window with a wooden shutter.</p>

<p>Never mattered to me because I almost never compress my images that aggressively. But interesting to know anyway.<br /> <br /> Thanks again for the mention of the article, Howard.<br /> <br /> Will</p>

<p>[Edited. In the first version of this post I was correcting something I thought I'd said earlier, then I discovered I'd cut that remark out.]</p>

<p>Detail in an image will dither the artifacts caused by heavy compression, William - it's on smooth, featureless areas that the artifacts have nowhere to hide. </p>

<p>Mostly a follow-up question, as I found this conversation when looking for what seems to be a similar question. I am not a professional photographer and I don't sell prints or images. But I am always a little torn on how best to present a file of an image for printing.<br>

Assuming I am cropping at least to some degree, is it best for me to submit the file for printing at full resolution/full size and just order the print in the size that I want it? For example if I want a 4X6, 8X10 etc. . . ? <br>

But these are different ratios, if I get a 4X6 vs. an 8X10. Does the "lab" then further crop my original (to shot ratio) or what? <br>

As you can tell, I have not done a lot of printing of my images, part of this is not being sure of the best manner is submitting the files.</p>

<p>Chris K. asks,</p>

<blockquote>

<p>Assuming I am cropping at least to some degree, is it best for me to submit the file for printing at full resolution/full size and just order the print in the size that I want it? For example if I want a 4X6, 8X10 etc. . . ? But these are different ratios, if I get a 4X6 vs. an 8X10. Does the "lab" then further crop my original (to shot ratio) or what? </p>

</blockquote>

<p> <br>

Chris,<br>

<br>

First, about resolution: More is better, most is best. If you're uploading an image to a printing service like Mpix or Bay Photo or whatever, upload the highest resolution file you've got <em>if the service will allow it.</em> Let the service downsize it. Now I think some services (especially those for amateurs) may hassle you about the size of your files. In that case, try using the calculation I mentioned earlier, where you multiple the inches on a side by 300 pixels to get the pixel dimensions of your image. In other words, if you want to order a 4" x 6" print, upload a 1200 x 1800 pixel image.<br>

<br>

Second, re cropping: This is indeed a bit of a problem. If you're ordering a print for yourself and you want it, say, 8" x 10", then the easiest thing to do is crop on your computer, to that 4x5 aspect ratio. I say this is "easiest" because the program you use to crop on the computer probably is easier to use and more precie than the cropping widget on a website. That said, many print-ordering services will allow you to crop on their website. For my clients, I almost always do a preliminary limited crop (if the image needs it), leaving wiggle room so that the resulting image can be given a secondary crop to fit the customer's desired print size.<br>

<br>

Will</p>