How do I make a photo's file smaller and take up less space on disk?

Transcript

We will move on to making files smaller in terms of file size. One of the common problems I hear about on AskLeo! are people who are attempting to mail photographs from one to another; share photographs via email and have the email bounce because the photographs themselves are so large. Their mail system happens to have some kind of a problem with the size of an email.

So, in this particular case, what we’re going to do is take a look at a photograph and take a look at some of the different ways that a photograph can be manipulated in order to make it smaller; not necessarily in terms of its physical size, its visual size (although we’ll look at that, too), but in terms of its actual file size.

So, this particular photograph (and I’m actually going to change the display here) you can see that this particular photograph that I took earlier this year – it’s a jpg file; it’s 4288 x 2848; that is the raw dimension, the full size, as it comes off of my camera and you can see that it is roughly two megabytes in size. Now, two megabytes isn’t a particularly large attachment, but in some cases, it can be. And in particular, if you’re sending several photographs, two megabytes adds up pretty quickly. I know of email systems that have as low as five or ten megabytes email attachment limits, in which case, adding just a couple of photographs could easily cause you to trip into a scenario where your email would bounce for being too large.

So, let’s go ahead and take a look at that photograph first – full screen – here it is. So, the first approach to making the file physically smaller; in other words, I’m talking about not visually, but the file size on disk to take that two megbyte file size and make it something smaller than two megbyte is to play with the jpg compression setting. So, what does that mean? What I’ve done here is so far I’ve simply started to do a File > Save As. In other words, I’m going to save a copy of this photograph. One thing that’s always important to realize is that you should never, ever save on top of your original because once your original has been overwritten by your edits, you can never go back. Typically, your original has the highest fidelity; the original ‘pre’ any changes, you just want to make sure you always give your changed files, your changed images, a new file name so as to preserve the original.

So, in this particular case, I’m going to go ahead and give this a slightly different name. And you’ll see why I say ‘quality’ here in a minute. What we’re looking for is this item down here – jpeg quality. Let’s go ahead and have a look at this. The jpg image compression format and it is an image compression format has an adjustment that adjustment let’s you trade off file size for picture quality. So at one extreme, we have the highest quality possible here and what we’re seeing is before and after saving the file are pretty much the same – they’re visually identical. What I’m going to do is take the quality bar and move it down to the far end. I’m going to go ahead and give this zero as quality. So what I’ve done at this magnification. One of the differences that you can see at this very low quality … here we go, let’s use 11 here as the quality because you can see visually some of the changes that have occurred to the picture.

Before, the picture looks as you might expect: very gradient; the color here is very smooth; the contours of the grass here look appropriate, in fact, we’ll zoom in here in just a second. As you can see, with this lower quality of 11, all of a sudden the gradient of the sky has turned into something extremely visible; very ‘steppy’. You can take a look at the actual blades of grass that have now become very ‘pixelated’ is one way to describe this. Pixelated and/or showing what are called ‘jpeg artifacts’ that’s a lot what these blocks running around the middle of this, otherwise, solid color.

So the bad news is that the picture looks worse than it did before. Depending on the type of picture, that may or may not matter to you. If your picture is more like the bottom half of this picture, then it may not matter that it is of low quality. If you’re looking to preserve what’s above, like say the gradient in the sky, then this low quality could in fact be a significant obstacle.

But the good news is take a look at the different file sizes. The original file size for this picture was two megabytes. This is now under 100K, so if I go back to the entire photograph … now you can do a nice side-by-side comparison of exactly what the difference means. You can send this one as two megabytes or you can send this one that has under a 100K.

Now, exactly how those changes get reflected in different programs and in fact, the math behind the different quality settings may vary from program to program. Take this up to something like 91 and you’ll see why I’m doing that here in a second. So, it’s one of those things that you’ll want to play with if you ever encounter this situation. But one of the things that’s worth looking at is just off of perfect quality. So, it’s currently set to 91 out of a possible quality of 100. And again, for the record, the numbers that are used may very well differ from program to program. FastStone is using a scale of zero to 100; I have seen ‘low, medium, and high’; I have seen ‘1 through 10’ but the idea is that somewhere, there is a slider; a choice; a way of defining what kind of quality you want to preserve in your image when you save it in jpg format.

So when we return this and we go back to this and say quality 91, the file size is (gosh) less than half of what it used to be, but it’s already under a megabyte and yet, it looks pretty darned good. In fact, I’d have to be looking at it very closely in order to understand what, just exactly what, if any, difference it made. That’s why I point this out – because for a small change in saved quality, you can end up with a significant decrease in file size that nobody will ever care about.

The neat thing about jpeg compression is not that it’s this wonderful mathematical way of compressing images, although it is. What it is, is a format that understands how people look at images and uses that to degrade the quality gracefully to maximize what you see as opposed to exactly how the bits are stored. One thing to point out (and it should be obvious by now given the types of things we’ve done to this photo) jpeg is what is called a ‘lossee’ compression. In other words, the more you compress it, the lower the quality you choose the more data that gets lost from the image. You end up with these artifacts; you end up with various pieces of information that describe the photo being ‘lost’ in exchange for the smaller file size. But obviously for photographs, it’s a very efficient approach to saving images, specifically images in as small as a file size as is reasonable.

So what I’m going to do here is I’m going to save this as 91, with quality 91. And I’ll go ahead and change the file name to once again indicate that I have set it to 91. And if we now go back and take a look at the two files, you’ll see here that we have two images; they’re both jpegs; the dimensions are exactly the same. We have not changed the visual scope of this picture at all. It is still exactly the same physical size when you look at it, but the file sizes are dramatically different. And that’s a very simple change that you can make by saving it in a lower quality jpg format.

Let’s take a look at the other approach to dealing with size. I’m going to go ahead and exit and re-enter FastStone to make sure that I’m working on the correct original as I expected. What I’m going to do this time is what most people think of when they think of making a picture smaller and that is I’m going to crop it. Now, I’ve talked about cropping in a different segment and sometimes you can do that for some very nice ‘artsy’ effects for example, and in this particular case, the result here of having the sunset and the person juxtaposed with the light. I think, personally, I like this cropped approach to the photo better. So I’m going to crop it. Now, if I just save it (by the way, I right-clicked on the photo this time. It’s the moral equivalent of heading over to the left-hand menu, left-hand edge of the photo where this menu pops up), but I’m just going to go ahead and right-click Save As. And this time, I’m going to call it sunset_cropped and you’ll notice that the quality is still at 100, so we’re looking at the exact same quality that we started with but a smaller, literally a smaller visual picture. Now when I go back and take a look at them, you can see that the cropped photo, which I’d say is less than half, actually less than a quarter, of the size of the total surface area of the original is actually not that much smaller than the original.

So my point here is simply that cropping a photo, depending on the complexity of the image within it, may or may not get you the file size reduction that you’re looking for. The data that’s in a jpg file is all about encoding what the image looks like and that can be or actually that does depend directly on the complexity of the actual image that’s contained therein. For example, when I cropped this photo, I cropped off a bunch of essentially solid black that was on the bottom. A big area of solid black doesn’t take that much in jpg to store it. The complexity of the image actually is remaining in the piece that I’ve kept. It’s the person; it’s the grass; it’s the gradient of the sky; it’s the light. So the information that is required to represent that photo even though it’s less than a quarter size of the original, a quarter visual size of the original is still fairly high. That’s why I say often a combination both of cropping (if you’re looking for a visual effect) and then adjusting the jpg size, or jpg quality, are typically the ways to go.

So, I think I’ve gone on enough about this off the top of my head. Let’s take a look at questions; I see that there are a couple in and if you have questions about jpg quality and formatting, by all means, now is the time to ask those.

I was wondering if you insert an image, say 1650 x 1275, into the body of an email as a .png, and then resize it by dragging the sides of the picture, will the resized image appear in the recipient’s email? Unfortunately, that’s not something that I can answer because that actually depends explicitly on the email program that you happen to be using. Now, I’m going to run off with one example because I happen to know how it works – Word, Microsoft Word allows you to drag and drop pictures into your documents. What is preserved in the document is the original file. The image itself is not modified. In other words, if you’ve got this huge 4K by 2K image and you drop it into a Word document, no matter how you scale the image in the document, in other words, if you drag it to make it bigger or drag it to make it smaller, the entire image is still there. Word is actually adjusting the display of that image when it’s displayed, not when it’s placed in the document. Since Outlook in the past has used Word as its email editor, and I believe whatever Outlook is doing these days, I believe that they’ve dropped Word, but they’ve got something equivalently complex behind the scenes right now. I believe that would do the same thing. You may scale the image all that you want in the email message, but it’s the original file that’s been dropped into the email message to begin with. Now, what does the recipient see is the other half of that question and once again, we can’t really even give you a straight answer on that because it depends on what email program the recipient is using. Typically, and I say this on average, they’ll get what you send them. If what you see when you hit ‘Send’ is a scaled or cropped or whatever image, then typically, the recipient will see the same thing; they’ll see what you sent. But it’s definitely not guaranteed. Images, emailing images as attachments are simple; embedded in an email are not. And by that I mean that when you embed an image in an email in the flow of your text, what happens then, I almost want to say it’s a crap shoot because the combination of email formats and email programs often render images, they often end up coming out other than you expected. Sometimes, they’ll show up as attachments; sometimes, they’ll show up as the original image, a very common question that I get is that people can’t see them at all except unless they forward the mail; it gets very complicated so that’s why I can’t give you a straight answer. I’m really sorry that I can’t. I wish that it were simpler when it comes to sending pictures like that. My recommendation for sending pictures, in other words, the approach that I suggest in general, for sending pictures from one person to another via email is not to drop the image into the body of your message. It may look pretty, but in fact, it reduces the probability that you’re recipient can see it. Now, once you’ve actually confirmed that the particular recipient is seeing what you’re sending, then fine, go for it, have a good time with it. But if you’re not sure, if you’re ever not sure, the only scenario that I know that is most likely to work is to attach photographs as attachments to your email. In other words, don’t put them in the body, but use your email program’s attachment function to then attach the specific jpg or whatever to the email and send that. But it doesn’t meant that recipient may have to specifically open the attachments in order to view the picture. Depending on their email program, they may be able to scroll below the body of your message in order to see the images. But it is the most reliable way of getting an image from point A to point B via email. Ah let’s see, another question.

I’m not familiar with FastStone. Please compare FastStone with other viewer programs. Is it free? Ah yes, it’s absolutely free. And what I’ll do instead of actually answering that question here is directing you to … in fact, I’ll just bring it up right now. I actually did one of these webinars on FastStone specifically so I have two articles that I’d like to direct you to. One is this one which is basically my formal recommendation of FastStone Image Viewer that basically walks through some of its features and gives you the download link. The other one that I suspect may also be interesting to you is this; this is a segment from a previous webinar and you can see in fact, I use the same picture that basically walks through using FastStone for some of the other, many of the things you might want to do with it. So I’ll direct you to those two and as you can see, all I really did was go to my search and search for FastStone and those two came up as the top two search results.