Exporting Images from Lightroom

Why is the concept  of sizing or setting the aspect ratio of images for print so difficult for some people to grasp? I don't get it. So here's an attempt to address the issue in a way that might help people understand it better.

Pixels-per-inch or Dots-per-inch

This comes up OVER and OVER and OVER again and people do not understand it.

The pixels-per-inch (ppi) box is only useful to people who specify their image sizes in INCHES and not in pixels. If you tell Lightroom (or Photoshop or any other program) that you want a picture to be 10 inches wide and 300 ppi, that means you are telling it to give you a 3000 pixel wide image. If you want  you can do that, but you could also tell it you want to print a 100 inch wide image at 30 ppi and you'll get EXACTLY THE SAME IMAGE. Or you could just tell it to give you a 3000 pixel wide image and it doesn't matter what you put in the ppi box! Here:

One of these images is 819 pixels x 1024 pixels at 1 (yes, that's ONE) ppi. The other one is 819 pixels x 1024 pixels at 1,000 ppi. Can you tell which is which? No you can't. THEY'RE THE SAME. Keep reading...

Added after the fact: This post is getting a LOT of hits because this question seems to come up a lot on Facebook. Both the Aspect Ratio and the Print Resolution questions. If you find this useful, please consider clicking the donation request at the bottom – purely optional but it would help! At least, I would ask you to subscribe to my newsletter (it's free and you can unsubscribe with one click if you must). Here's the link  

Now let's look at the ASPECT RATIO, or in plain English, the SHAPE of the picture.

Suppose this is the original picture:

This image is copyrighted and the property of the author. If you want to use it for any purpose whatsoever, you need written permission. Email me. If you want a print, I'd be happy to accommodate you at a very reasonable price. Please don't rip it off.

It's ASPECT RATIO (that's the technical term: maybe it's easier to understand the word "SHAPE") is 2:3. What does that mean?

For every 2 units high, it is 3 units wide. When it came out of the camera it was 4912 pixels high x 7360 pixels wide. That's out of a D800 so it's 36 million pixels if you multiply it out. If it came out of an old D70 it would be 2000 x 3008 pixels: only 6 Megapixels, but exactly the same shape — 2:3*.

* for all intents and purposes. I know neither one is EXACTLY 2:3 but we're splitting hairs here.

A Canon 60D has a resolution of 3456 x 5184 pixels. Do the math: guess what the shape of the image is? That's right, 2:3. Pretty standard in the DSLR world. Your camera might be different but let's go with this example.

OK, what if you wanted to print this picture without cutting ("cropping") anything off the height or the width of the image? What shape would the paper you're printing on have to be?

If you said 2:3 then you're staying with me! Can you think of some examples of paper that is that ratio? Look at this list:

• 4" x 6" (10 cm x 15 cm)
• 5" x 7" (12.5 cm x 17.5 cm)
• 8" x 10" (20 cm x 25 cm)
• 8" x 12" (and so on...)
• 11" x 14" 
• 12" x 12"
• 16" x 20"
• 16" x 24"
• 20" x 30"

Which ones are the right shape? Do the math, I'll wait right here...

If you said the 4x6, the 8x12, the 16x24 and the 20x30, now you're cooking!

So what happens if you try to print that picture on an square piece of paper, say 12"x12", for example. One of three things:

1. the image can completely fill the paper, but some of the width will get cut off. In other words, you're printing the full 12" height, but there's only room for 12" of width so the other six inches are going to get cut off (remember your picture is 2:3 shape, so if it's 12" high it's going to be 18" wide).





2. you can squeeze the 18" width of the picture into the 12" width of the paper, but then you'd be squeezing the height too, so the height will only be 8" high and there'll be a 2" band of unprinted paper above and below the picture, or






3. you can squeeze the width of the picture without changing the height, but this distorts your picture (you'd have to get fancy in Photoshop to do this, though)

Get it? So it's your choice how you want the image to be printed (nobody ever uses the third choice), with some stuff getting cut off or with some unprinted paper. Make sense?

So what should you do to make the picture fit the paper? It's up to you, of course. Chances are it isn't going to get cropped the way you like it by the printer, so you should decide in advance and change the shape of the picture to match the shape of the paper. That's called "CROPPING" and you do that in Lightroom in the Develop module. 

The red arrow shows you where to click to get the crop tool. The blue arrow shows where to click to get the dropdown menu that you see with the different shapes 

So do the math – it's basic grade 4 arithmetic – and figure out what aspect ratio you want. If you don't see it there, you can click "Enter Custom" and put in your own numbers, so if you want your own special size, that's where you can do it.**

** This isn't limited to printing, you know. For example, the shape of the header at the top of this blog is 1280 x 350 pixels. If you look closely at the list, you'll see "3.657 x 1" which is that shape. You don't actually have to do the math, you could just enter 1280 x 350 and Lightroom will do it for you!

Added Later:

A good workflow practice in Lightroom would be to create a  "Virtual Copy" of the image if you're going to produce different crop shapes. Then work your magic on that copy without affecting your original. You can't rename the virtual copy without renaming the original but you can put something in the "Copy Name" field in the metadata, like "square version" so that you can search for it later. 

Summary:

So now you should understand why, when you try to print your 2:3 ratio picture on a piece of 5x7 paper, some of it is getting cut off. The only way to prevent that is to print it like the second example above. Or you can decide to cut it off wherever YOU want by cropping in Lightroom. So far so good?

Now let's look at RESOLUTION.

You're probably looking at this article on a computer screen (OK, maybe on a tablet or phone, but let's go with the easy example!)

When you set up your computer, you chose the screen resolution (or, let's face it, you accepted whatever you got when it came home from the store). Depending on what kind or shape of monitor you have, you might have selected 640x480 pixels (if you did, you're older than me. And trust me, I'm OLD!). Or 1600x900. Or 1280x1024. Or some other number. My 26" Samsung monitor is set for 1920x1050 pixels.

Now just to confuse you further, my "26-inch" monitor is really only 23½" wide. The 26" is a diagonal measurement. But let's divide that 1920 pixels into 23½", we get about 81 pixels per inch. The universal standard for computer monitors and the Internet is 72 pixels per inch but who's counting? Close enough.

You could quibble with me and tell me you have a fancy 'Retina' display or a giant monitor, or a $500 video card that lets you see 4000 pixels on your screen but hey...

Now go to the top of this article and read what I said about the resolution of the owl picture as it came out of my camera. Wow. 7360x4912 pixels! If I tried to look at every pixel of that on my computer, it would be dripping out of my monitor and down both sides of my tabletop! So guess what? I CAN'T look at them all. I can only squeeze them into the 1920 pixels (wide) that are available to me.

OK, now go find a magnifying glass. I'll wait right here. Are you back? Now look really closely at your computer screen. See how it looks like a bunch of little square dots? Those are called pixels.

So if I want to output a picture for use online or just to be viewed on a computer or tablet, I don't need it to be any bigger than about 2000 pixels (wide). Otherwise it's a waste anyway, you can't see the in-between ones. Since you probably aren't looking at any pictures at the full width of your monitor, even that big is a waste. Make them smaller!

Facebook is special. They have some nasty compression algorithms that mess up pictures. If you research it, you'll find that the best size to make a picture, to optimize how it looks on Facebook, is 2048 pixels. Don't even think of asking why.

Your computer is smart. You don't have to tell it how many pixels per inch to make the picture, that's determined by the computer and the monitor. Even if you tell it you want 10,000 pixels per inch it can't do it! It's going to change it to 72 ppi (Pixels per inch) for you. The important thing for you to decide is how many pixels (wide, for example) you want the image to be. Half a screen width is about 800 pixels. What about if you only output your picture at 200 pixels wide, and then tried to blow it up to full-screen (your browser can do it, for instance)? Then it's going to look all unsharp and fuzzy because there's not enough information to exactly light up all of the pixels. Get it?

So if you're outputting a picture for the internet, somewhere between 800 and 2000 pixels is best. Of course the bigger you make it, the bigger the image file size becomes, the slower it is to load, etc. Your call...

I choose to make my pictures 1280 pixels wide for this blog. Here's what my settings look like in the Lightroom export module:

The internet, and your computer monitor, all work in the sRGB colour space. If you set it to something else, your colours are going to look funny. And generally you're going to want JPEG image files, the internet likes them the best. 

Understand that your files inside Lightroom are probably not going to be that size. For that matter, they won't necessarily be JPEG's, they may not be in that colour space... they're your NEGATIVES. You need to EXPORT the pictures from Lightroom to use them for anything, and this is where you get to tell it what kind of files, what size, etc.

Now what about for printing?

Go get your magnifying glass and a photographic print. Do you see a bunch of little pixels? (If you do, you're not looking at a photo print, you're looking at something reproduced on a printing press, not an inkjet or giclée printer). Your printer has a bunch of little nozzles that spray ink on the paper but in a really teeny-tiny pattern. Some of the better ones might spray up to 1400 ink dots per inch! (DPI stands for "DOTS per inch". PPI is "PIXELS per inch". One's for ink, the other for screens).

I'm not going to get into how the ink spreads as it soaks into the paper, or how it blends together with nearby dots. Suffice it to say: the universal standard for not being able to see the little individual dots is 300 DPI. Some people use 240 DPI, some use 360... but let's call it 300 to be safe. If you have less information than that the in-between dots are going to take on an average value, not the right value, so your picture will get fuzzy.

Here's the same owl shot but I saved it at only 128 pixels wide then blew it up. The same thing happens if you don't have enough pixels to print! And you need a lot more for printing than you do for displaying on-screen! 

Doing the arithmetic, if you want a sharp 8x10 print, you are going to need 300x8 dots by 300x10 dots, or 2400x3000 pixels. For a 16x20, double that. For a 20x30, you need 6000x9000 dots. That's more than most cameras can do but Adobe, who makes Lightroom and Photoshop, and a bunch of other companies know how to intelligently upsize your pictures. The person who REALLY knows how is the company that you're sending your images to print! Always ask them what they want when your image is undersized.

Where were we... by now, you understand that the really important number is how many pixels (or dots) your picture contains. Just like your monitor, that printer will change the number of dots per inch to whatever it has available. If you give it only 1500 dots and you ask for a 10" print, you're only going to get 150 dots per inch (which surprisingly, isn't bad most of the time!).

If you give them too many pixels, don't worry! The printer is smart (not necessarily the person pushing the buttons, the machine!) and it will figure out what to do with the in-between ones, just like your monitor does if you give it an oversized picture. The files might be too big, though!

Why does Lightroom have that dreaded resolution box I marked with an "X" above? It's for people who would prefer to output pictures of a certain size in inches (or cm) and then you have to tell it how many pixels per inch to render. If you do the math yourself, and specify the image size in pixels, that box doesn't matter.

Here's one of my typical settings for going to print (it does 14" on the long side at 300ppi). Note that most printers like JPEG/sRGB as well, but talk to your print shop!

So get in the habit of figuring out how many pixels or dots you want. Let the computer do the rest. Or, choose the size of the picture you want in inches (or cm) and tell it 72 ppi for screen or 300 ppi for printing.


BIG SUMMARY.

In Lightroom, first choose what SHAPE you want the image to be using the crop tool in the Develop module. Next choose what SIZE it should be in pixels wide x pixels high, using 72 ppi for use on screen or 300 ppi for use in print in order to make your calculations.

If you're going to be printing different sizes and shapes, it's probably smart to create separate output files for each version and virtual copy is one way of doing that and staying organized.

Make sense?

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Lightroom Performance and Previews

This article was written in response to a request from the Admins on the Facebook "Lightroom Q&A" group. 

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Note: I use Lightroom 5 (version 5.7 at this writing) and Photoshop CC 2014. Some of these functions also work in earlier versions of the programs. I run on a PC, not a Mac but they're almost the same in Lightroom.

Lightroom sometimes appears to respond and process images slowly. Some of that is due to your preview settings, which you can change to match your needs and available hardware.

Right after importing new images, people sometimes complain that when Lightroom opens a RAW file, first it looks sharp, then it looks ugly for a while, then it gets sharp again, especially when viewing the image larger than grid view. What's happening?

That exact sequence really only happens on newly imported files, where Lightroom hasn't yet had time to generate the standard previews. First thing you see is the JPEG view that is embedded into the RAW file by your camera. That gives way to the unprocessed RAW file while Lightroom churns away in the background to generate the 1:1 preview. Finally you'll see the image in all its glory, including edits you've made inside Lightroom.

You may also see a delay in seeing this full quality image when you view an image in a larger view (like Loupe, or in the Develop module, or especially when you zoom in to a 100% view). Again, Lightroom needs the 1:1 preview and may ask you to wait while it's being generated.

Importing new images

In the process of importing new images, Lightroom's overall performance might appear to be slow because it's working in the background, using computer resources. One of those things is generating the full 1:1 preview you use whenever you zoom in on an image. You can improve that performance by delaying when that happens (you can do that at any time from Library → Previews in the main top menu). Here's what the upper right corner of your LR screen looks like just before you tell it to start importing:

You have four options here. These are the settings I use. I always make a second copy of all images to a different hard drive – in this case the internal drive in the computer (the originals are stored on an external drive). I want Smart Previews for all my images so I can edit them when that external drive that contains the actual images is not plugged into the computer. I don't tell it to block suspected duplicates because in my workflow, I format all my camera memory cards after the pictures are safely imported: if I forget, that's my problem!

I tell Lightroom to build 1:1 previews for all images during the import process. If I wanted to make importing faster, I would select "Minimal" previews or one of the lesser sizes. But I don't shoot NFL football games where I only have minutes to process and cull thousands of images during halftime. When I do an import, I generally plug the card into the computer, start it going, then pour myself a cup of coffee (or something stronger!) and give it time to get it done. 

Hard Drive Space

Now let's look at what those 1:1 preview files look like.

Previews take up some hard drive space. But not that much, in the grand scheme of things! Remember that Lightroom is just a glorified database: it does NOT contain your actual images, just pointers to tell it where to look for them, just like that card file in the old public library tells you which shelf to look for when seeking a specific book.

This Lightroom Catalog is my main one. It contains 63,423 images as I write this, many of which are 40 Mp giant RAW files from my D800 (not that it matters what size the images are to the catalog!). If you ever want to know WHERE your LR catalog is, you can bring this dialog up by clicking "Catalog Settings" on the "Edit" menu in the Nav bar at top left (may be a bit different on a Mac). So I have almost 3 Tb of images (3000 Gb) all listed in a 2.47 Gb ".lrcat" file in my internal hard drive.

I don't want to stray too far off-topic here but this is a screenshot of my catalog folder on the hard drive. The Lightroom catalog itself is 2.5 Gb. When you're backing it up (or copying it elsewhere) THAT is the file you need to copy. The two .lrdata preview files are not important to back up, Lightroom will regenerate those. The Catalog Preview file is relatively big: 13 Gb in this case. 

Now my Catalog Previews file is ONLY 13 Gb because I've chosen to manage its size. If I had full 1:1 previews from all 63,000 images it would be much bigger. Here's where you manage that.

In the same place as before (Edit → Catalog Settings), open the "File Handling" tab. You have three choices you can make about your previews. 

The first line is about the SIZE of the preview.

My biggest monitor is set to 1920x1080 pixels. I chose a preview size so I could see ALL of those pixels, so just larger than the screen. If you have a lower resolution monitor, you don't need the preview to be that big.  

You can also choose the preview quality. I find "Medium" to be good enough for me. Remember, you're not changing the image, just how you view it onscreen when you zoom in to edit. When I do a really fine edit, I switch to Photoshop.

Now here's the big space saver. You get to decide how long the huge 1:1 previews stay on your computer.

In my case, I decided I don't need the 1:1 previews instantly available on images I'm not currently working on. So I tell Lightroom to discard them after one week.  

Performance

When you click on an image in Loupe view or Full Screen, or in the Develop or Print or Slideshow or Web module, and especially when you zoom in, Lightroom needs that 1:1 preview. So it takes some time to generate it if you have discarded it. Once it has, it'll keep it around as long as you've told it to in the above menu.

Adobe has a resource page if you want to read more on this subject. It's here: https://helpx.adobe.com/lightroom/kb/optimize-performance-lightroom.html

To summarize: 

If you have tons of hard drive space, go ahead and keep your 1:1 previews forever. If you have limited RAM or CPU speed, you may want to hold off generating them immediately on import. Lightroom can churn away in the background if you tell it to (Library → Previews from the main top menu) or when you decide to look closely at an image. It all depends on your hardware resources and your workflow requirements.

Does that make sense?

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