Saving images for the web

As can be expected, large images take longer to load. When I say large, I’m referring to file size rather than the dimensions of an image, i.e. the value in KB, MB, GB etc. Seeing as 47% of users expect a webpage to load in under 2 seconds, and 40% will abandon a page that takes more than 3 seconds to load, it’s important that your images are small enough to ensure a speedy site.

There are three things you can do to properly optimize your images for your online store:

1. SAVE THE RIGHT DIMENSIONS

You must open the image in Photoshop and view it at a 100%. This allows you to view the image at the exact size it will be displayed on a computer monitor when you save the image for web.

2. SAVE IMAGES FOR WEB

It’s possible to reduce the file size without significantly reducing the quality of your images. My favorite method of reducing file size without significantly reducing the quality of the image is to use use Photoshop’s ‘Save for Web’ function. Open your image in Photoshop and go to File > Export > Save for Web (Legacy)…. A window will appear which will allow you to choose your export quality. I find that a quality of 60 works best because it drops the file size down to below a megabyte and there’s no noticeable difference in quality.

3. COMPRESS IMAGES FOR WEB

Image compression apps are the easiest way to reduce file size of images. These types of tools remove hidden data in the image file like additional color profiles and metadata (like geolocation of where the photograph was taken) that aren’t needed.

These tools provide a quick and easy way to reduce files size without losing any image quality.

Image Compression Apps/Services

Saving an Image for Web – Walk-through Example

To begin, let’s pretend we are Stiff Salt (actually owned by a friend and Shopify Developer) and we wanted to change our feature image on our online store.

Stiff Salt

We set up a scene, make our salt look absolutely incredible and we take a photo with a DSLR camera. Great we have our photo. What a beauty!

Photograph Salt

But… the file size is HUGE! 14.6 MB to be exact. And the dimensions of the photo are 5184 × 3456 pixels. This is completely unusable right now. It’s literally big enough to print a movie sized poster. At 14.6 MB, this image would take significant time to load on a visitor’s computer. This is no good.

Image Size Original

It’s time to get to work and reduce the image size, and the file size – significantly.

Remember, we’re going to be doing three things to the image.

  1. Reduce Image Size (This is the dimensions of the photograph)
  2. Save the Image Appropriately to Reduce File Size (This is the size of the file and how much space it takes on your computer’s hard drive and/or your web server.
  3. Compress the Image File (To get rid of any additional hidden data taking up space)

REDUCE IMAGE SIZE

Depending on which program you decide to use, and personal preference, you can:

  • Reduce the image size before saving
  • Reduce the image size while saving the image
  • Save the image, then reduce the image size

To keep things simple, we’re going to first reduce the image size. To do this, I’m going to open the image in Photoshop (You can use whatever image program you feel most comfortable with).

To figure out what size, I looked at the theme’s suggested homepage image size. It was 1600×800 pixels (Remember the original was 5184 × 3456 pixels).

Shopify Theme Hero Image Size Suggestion

In Photoshop, I’m going to select Image -> Image Size.

Reducing Image Size

Ok, we’ve reduced the size (dimensions) of the image to something more appropriate and recommended by the theme developer.

SAVE IMAGE APPROPRIATELY (SAVE FOR WEB)

In Photoshop, there’s a specific command called “Save For Web” that optimizes the image file for displaying online. This is important as the regular “Save” command can end up creating file sizes 2-3 times larger than the “Save For Web” command.

In the “Save For Web” box, we need to make a few selections.

  1. Image Type: The file type will affect the quality and size of the output file.
  2. Image Quality: This is important and can heavily effect the final file size.
  3. Dimensions: We already did this in the first step, so there’s no need to do it again, but if we didn’t do this in the first step, we could just change the dimensions for the image here.

Based on what we learned at the beginning of this post, we know that JPEG is the best file type for photographs, or any image with lots of colors and complexity. We will select JPEG.

Save For Web Command

For Image Quality, you have a scale you can select with 5 presets that range from Maximum to Low. Let’s take a look at the final output file size of each of the quality levels (this information is displayed in the bottom corner o the image saving window):

  • Maximum – 1.38 MB
  • Very High – 611 KB
  • High – 339 KB
  • Medium – 152 KB
  • Low – 86k

You can see that for every quality level you go down, the image size reduces by nearly half. In general, I’ve found that High is best setting for most images. At this level, it’s nearly impossible for the human eye to see any degradation in image quality, and the file size is nearly 4x smaller than if we were to just select maximum.

If the image is an extremely important image with a lot of detail, you may want to select a level higher and save at Very High.

Essentially, saving for the web is a balancing act — you must balance the quality of the graphic and the file size of the media to suit your personal needs.

PRO TIP: As a general rule of thumb, I like my product photos to be a maximum 80-150 KB, and for large homepage hero images to be a maximum of 250-350 KB. Those are good benchmark numbers for you to aim for as well.

Photoshop - Save For Web - Low

COMPRESS IMAGES FOR WEB

If you used Adobe Photoshop, it will have already done a really great job at reducing the image size, however, you can still likely shave off another 5-10% of image size by using a compression app like ImageOptim.

ImageOptim is also the easiest way to quickly reduce image file size, if you have used another program to save your images that isn’t as good as Photoshop.

Dropping each of the files from the previous step into ImageOptim, I was able to further reduce the image size by another 5%. Not huge, but again, these were already optimized with Photoshop. Regardless, every KB counts.

ImageOptim

To view the original full-size, uncompressed image as well as each compressed image to inspect the image quality difference for yourself, click here.

Conclusion

To recap, our photo was insanely huge when we started. However, with a few simple steps, we reduced the photo size from 5184×3456 to 1600×800 so that it’s a perfect fit for our homepage, and at the same time, took it from a computer-crashing 14.4mb, down to a much more reasonable 336kb

Saving images appropriately for the web is an important step to learn early and implement religiously. Even if you only save 10-20% on each image, over time, as your store and website grows, every little KB can add up to some significant savings that will lead to a much more pleasant overall experience for your visitors, customers, and Google.

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