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So as your documents contain more and more layers, those file sizes for those documents will increase sometimes quite dramatically. So people are always asking me, when would you want to merge your layers down, or when would you want to flatten your image. Honestly, I think that the flexibility that you get by keeping all of your layers separate far outweighs the benefit of any decrease in size. So let me show you just two things. When I go here to my small images, these images over here to the right, remember, we converted those into Smart Objects.
So that means that Photoshop is holding onto a lot of information. In fact, if I want to see the original Delta image, I can just double-click on the thumbnail for the Smart Object and Photoshop will bring up that image in its own window. So I'll click OK here and now we can see I have a new tab. This is the Delta.psb file. This is the Smart Object that's contained inside of this WindowSeat02 file. So let's click back on the Delta and let's just go to Image>Image Size and see how large this is.
So we're talking 1200 pixels x 1200 pixels, so really it's not that large, but you can imagine if this was a much bigger file, then this would be a bigger number. So when I click OK here and we close this. Well, if I want to see how many of those pixels I'm actually using, I can choose Edit and then Free Transform. And up here in the Options Bar we can see that I've scaled this down to 24% of the original image.
So Photoshop is actually keeping track of a lot more data than is actually being used in this image. Let me cancel out of here and we'll talk about our options. So my option would be to rasterize this layer, which would then throw away all of the extra information. If I rasterize the layer though, and then I want to scale this up, I'm not going to have the image data there to provide me with the quality that I would want. So if there's any doubt in your mind that you might need to scale up these images later, I would suggest that you do not rasterize them.
But if you know for a fact that these images are not going to change size, then we could right-mouse click on the layer and choose Rasterize layer, or you could use the layer menu and then choose Rasterize and you could rasterize the Smart Object. You'll notice here you could also rasterize the layer or all of your layers. I'll go ahead and choose Smart Object. You can see that the icon changed here on the Layers panel, so that's no longer a Smart Object. And if we do use Free Transform, you can see here that the quality is not going to be good when I sample it up.
I'm going to Undo the Free Transform and in fact, I'm going to go back one step further, I'm going to step backwards so that I still have my Smart Object here. So the other question that people ask me is when would you merge your layers together? Well, certainly if these three layers are not overlapping, I could select all three layers in my Layers panel, and if I were to choose Merge layers, Photoshop is going to do two things. It's going to merge them down to a single layer and it's also going to rasterize them.
So I would see a decrease in file size, because I'm no longer holding onto those Smart Objects and it's going to put them all in one layer. But again, you're going to lose some flexibility here. This makes it much more difficult if I want to swap the position of two of these layers. Right now, they're on the same layers, so I'd have to select one and use the Move tool and move it around, whereas, if we just Undo that Merge layers, you can see if I want to reposition the Ice layer, I can just scoot it up, now it's underneath the Delta layer, but that's okay.
I'll grab the Delta layer and just scoot that down. So if you want to maintain that level of flexibility where you can make changes like that, I would suggest that you don't merge your layers together. Finally, what about flattening your image? So I think flattening your image, well, of course it's going to eliminate any ability to move around individual layers and it's also a little bit dangerous, because if you're not paying attention and you go to layer and you Flatten your Image and now you do a Save, well, you're going to save over your layered document.
So instead of flattening it and then trying to do a Save As, I will Undo my Flatten Image and I'll simply choose File>Save As, and in the Save As dialog box, I can choose to Flatten the Image. For example, if I'm going to save this as a JPEG file, well, a JPEG file can have layers anyway, so it's going to automatically Flatten the document. But here's the key difference. It doesn't flatten the document you have open. It's going to flatten the document that you're doing a Save As to.
So I would rename this and typically I would put the word Flat on my flattened documents just to tell me very quickly if I'm looking at them, say in Bridge, that this is the flattened version. I also know it's the flattened version, because it's got the .jpg and JPEG files can't be layered. So when I click Save, you'll notice that Photoshop is going to save out a copy of the flattened version. It's not going to replace what I'm seeing here. So we'll click Save, I'll pick my JPEG Options, but I'm left with my layered document as my open document.
If we switch over to Bridge, we can see that here is the copy of my image that's flattened and saved as a JPEG. But if we return back to Photoshop, I'm still working on my layered Photoshop document. So there you have it. If you want to maintain the most flexible workflow, I would recommend that you don't rasterize your layers and you don't merge them down. Instead, keep all of the different elements in your composite on separate layers so that it gives you the flexibility to change your mind later on.
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