Ok, so you are married, the honeymoon is behind you, gifts are opened, and now you find yourself up to your newly married smile in photos. Or more accurately, digital images, stored on a dvd, a flash drive, a memory card, etc. From your professional photographer, from your bridesmaids, from your dad, your Aunt Betty, cousin Tony… Potentially thousands of images. And you stop to think – “huh, I am not a photographer, what am I supposed to do with these things?”
Well a little bit of information at the beginning can save you some heartbreak down the road. Most of the time, (like nearly ALWAYS!) these photos – that you cherish – are saved as a specific file type, one you may be familiar with – called a jpg. That’s a good thing… it is convenient, familiar, easy to share and easy to use. But did you know that there is also a dark side to jpgs, with the potential for you to be damaging these images, just by saving your photos again as a jpg? Huh!
Jpg (if you really want to know) stands for the Joint Photographic Experts Group. Blah blah blah. But what you may want to think on for a moment – is the fact that when you save your photo as a jpg – you are compressing the information in your image. Why? To make those files smaller, easier to use, & easier to store.
Now compression alone is not the issue. But jpgs use a type of compression called ‘lossy’ compression. Lossy compression reduces a file by permanently eliminating certain information. When the file is uncompressed (aka opened), only a part of the original information is still there.
SO what does this mean to you? Well lets imagine this…
- you get amazing photos on a dvd from your professional photographer
- you copy them all to your hard drive, and get to work – getting creative with them, by cropping some, playing with black & whites etc. Any images you made changes to you save, naturally.
Problem # 1 – when you make changes to a jpg and save it, you are throwing out some of the detail of the image. How much? Well remember that slider where you choose a bigger / higher quality jpg vs a smaller lower quality jpg? Well you are choosing how much info you are chucking. But whether you choose big or small, you are without a doubt tossing away some amount of image detail.
- next you email that cropped B&W photo to your mom, who opens it, changes something, renames it & saves it again.
Problem #2- Mom has now re-compressed an already compressed file, so that now the image is significantly degraded from that amazing photo you first saw form your professional photographer.
- your mom emails that same photo to your aunt… and so on…
You know where I am going with this!
So are jpgs evil?
No way. They are fantastic when you know how they work, and how to avoid their pitfalls.
Then what to do?
Think about your intended use for the image. Is it simply to use on face book? Fine detail is not a crucial issue. Making a large wall print at your local lab? Work from your original image file (meaning go back to your dvd), and consider saving it as another lossless file type, like a tiff. Or change nothing and continue on, tossing image detail with careless abandon. But do it with knowledge and a happy heart.
Now off you go, order prints & albums with your newly married smile, and look back on your detail filled wedding photos often!
FYI… from http://graphicssoft.about.com/od/formatsjpeg/a/jpegmythsfacts.htm
A quality setting of 100 does not degrade an image at all.
False. Saving an image to JPEG format, always introduces some loss in quality, though the loss at a quality setting of 100 is barely detectable by the average naked eye. In addition, using a quality setting of 100 compared to a quality setting of 90-95 or so will result in a considerably higher file size relative to the degree of image loss. If your software doesn’t provide a JPEG preview, try saving several copies of an image at 90, 95, and 100 quality and compare file size with image quality. Chances are, there will be no distinguishable difference between the 90 and 100 image, but the difference in size could be significant. Keep in mind, though, that subtle color shifting is one effect of JPEG compression–even at high quality settings–so JPEG should be avoided in situations where precise color matching is important.
If I compress a JPEG at 70%, then later reopen it and compress it at 90%, the final image will be restored to a quality setting of 90%.
False. The initial save at 70% introduces a permanent loss in quality that can’t be restored. Saving again at 90% quality only introduces additional degradation to an image that has already had considerable loss in quality. If you must decompress and recompress a JPEG image, using the exact same quality setting each time seems to introduce little or no degradation to the unedited areas of the image.
JPEGs lose quality every time they are opened, edited and saved.
True. If a JPEG image is opened, edited, and saved again it results in additional image degradation. It is very important to minimize the number of editing sessions between the initial and final version of a JPEG image. If you must perform editing functions in several sessions or in several different programs, you should use an image format that is not lossy (TIFF, BMP, PNG) for the intermediate editing sessions before saving the final version. Repeated saving within the same editing session won’t introduce additional damage. It is only when the image is closed, re-opened, edited and saved again.
JPEGs lose quality every time they are opened and/or saved.
False. Simply opening or displaying a JPEG image does not harm the image in any way. Saving a JPEG repeatedly during the same editing session (without ever closing the image) will not accumulate a loss in quality. Copying and renaming a JPEG will not introduce any loss, but some image editors do recompress JPEGs when the Save As command is used. To avoid more loss you should duplicate and rename JPEGs in a file manager rather than using “Save As JPEG” in an editing program.