Image Resolution Part 3 = file types
PowerPoint Tips — Image Resolution Part 3 = File Types for import into PowerPoint
Over the last decade, not much has changed in the type of image files you can import into PowerPoint. Clicking on the image below, will show you that the order of preference is the only thing that has been modified. Vector files and raster images with a smattering of mixed formats. A previous post explains the difference between raster and vector formats.
Picture file types to import into PowerPoint from version 2003 to 2013 (click to enlarge)
First thing to do is to verify the type of file that your software can export. If you are using Photoshop, it can export a whole slew of file types. It depends on the type of image you have, the amount of KB you are willing to accept, the quality of the rendering… I will attempt to clear a few fuzzies about all of this.
JPG with compression set at 80% is best for photos
JPG or JPEG, the acronym stands for Joint Photographic Expert Group. It has been around for quite a few decades, at least 1995, which is when I started surfing the net. At that time, it was one of the only file format that had more than 256 colours and some compression possibilities. Developed for photographs, not flat colour graphics. The size of photo files used to be a big issue, when bandwidth was tiny. Not so anymore. The advantage with JPG files is that the quality and file size (KB) can be controlled. The two variables are inversely proportional, that is, the more compression is applied, to try and get a smaller file size in KB, the more distorted the image will appear, detail will disappear and weird artifacts will show up. All those PowerPoint shows you receive in your mailbox, set to music, with beautiful but grossly distorted images, well, they look like that because of excessive compression. Alternatively, no compression will give you zero distortion in your pixels, but a fairly large file size. I have found that compression set at 80% is acceptable in reducing the file size while maintaining excellent image quality.
Limit your compression to 80% for JPG files
Alternate slider value would be 9 of a possible 12, or 75% compression ratio.
This slider allows 75%, which is quite respectable for image quality
The image below shows varying percentages of JPG compression. The first image is the ratio I mostly use. That last one set at 0%, truly, has lost all of its detail.
80% JPG compression reduces the file size by a fair amount but does not reduce photo quality too much. Best compromise.
PNG is great for logos and flat colour graphics with transparent backgrounds
PNG, aka PING, Portable Network Graphics came on the scene a bit later. It was developed to replace the limiting BMP, which had an awful limit of 256 colours (yuk). PNG has saved the day. Great for logos and icons that need to be moved around on your slides – legend icons on a map, etc. In most instances it looks better than a transparent vector file, which can also be used for flat colour area images. The file size is small on a PNG and the lossless compression allows smoothing on the edges. When I use PNG for a logo, I will allow myself the luxury of saving the image much larger than necessary, and scaling it down quite a bit on the slide. It will print well and project well.
The image below is a screen grab of part of a slide. The transparent logo image, was saved from the original EPS file in Illustrator, as a transparent PNG file, 1000 pixels wide. It was reduced, scaled down on the slide to 23% of its original size. It projects well, prints well, and can be placed overtop any photo.
A transparent PNG logo placed on top of a photo
EMF, WMF, vector formats used for more than just clipart
EMF = Enhanced Metafile, WMF = Windows Metafile, and their accompanying compressed cousins. These are the formats that Windows OS / Microsoft uses for vector-based clipart. Not my favourite type of artwork. If you must use clipart, take the time to modify the colours to match your branding. And stick to one style throughout your slide deck… otherwise, you get into the kitchen sink effect. Not recommended! This file type can also be used for icons, logos, flat colour graphics needing a transparent background, similar in effect to a transparent PNG file, but as a vector equivalent. The smoothing at the edges may not be as nice in some instances. Something to test for each file is different.
In some instances, I may save a well built vector map from Illustrator to EMF format, for use on a slide. It has the advantage (if properly drawn, and not too complex) of letting the user select specific elements and recolour each item individually, directly from within PowerPoint. See the screen grab below, where one land mass has been selected, and can be recoloured if its status changes for the company. A file type not to be disregarded.
Recolouring EMF files within PowerPoint
EPS, a universal format that can mix vector and raster images
EPS = Encapsulated Postscript File – a huge and complicated vector and raster mix. I typically get these files from engineers, working in weird and wonderful software. Usually, their knowledge of branding and colour choices is limited and the task remains for me to make it look like the rest of the content on their slides. Illustrator is the best software to use for this task, and usually involves tedious recolouring, on minuscule item at a time, in a stack of layers a kilometre high. In most instances, I will export the fixed file as a transparent PNG for use on a PowerPoint slide. Otherwise, all you are doing is taxing the laptop, slowing it down to read each and every single item in the file. Sometimes, company logos will be exported as EPS, then the task is much simpler, to convert to either EMF or transparent PNG, whichever looks best on-screen.
BMP is a huge and old format which can be disregarded
BMP = Bitmap – huge file sizes is what i recall. A 640×480 image file saved as BMP was a whopping 900 KB! The same image saved as JPG – 80% only 150 KB. If you must use a BMP image that you have located somewhere, resave it as something else, if it’s a photo – use JPG, if it’s a flat colour graphic – use PNG.
GIF is an oldie as well, and still used for minor animation needs
GIF = Graphic Interchange Format. GIF was great because it allowed for animation. It also had the transparency option. But it was only 256 colours. Still used today, but in limited use. Makes me giggle everytime I see the hoover animation below. One of my best. A colleague had written an article for the Bell Canada website, about the constant need to renew content on a website, to stay up to date, be pertinent, to do your housekeeping, keep it clean…
All other formats have a random occurrence around the office.
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Champagne Design — PowerPoint Design 
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