Note: I don’t talk about the technical side of photography on the blog much, but I LOVE helping people learn photography, so I’m starting a completely irregular (as in I’ll answer questions as they come in) regular segment on the blog called, “Photography? What the hell is that?”
Mitch asked, “What photo size/resolution is best? What is standard? I wonder at what size I should be saving my photos…”
It’s kind of complicated, so I’ll start with the simple answer.
You should save your photos at the largest size/resoluation and highest quality available to you.
To understand the complexity behind this we’re going to answer the following questions:
- What is image resolution?
- How does it relate to the file size?
- How does file format impact this relationship?
What is image resolution?
Image resolution is dictated by the size of the image sensor, and is measured in megapixels. (A megapixel is a million pixels)
Your image is actually a map of pixels. A pixel is like a dot. Do you remember sitting too close to the television back before all these HDTVs rolled in? When you sat too close to the TV you could see all the little rectangles that made up the picture on the screen. That’s exactly how our digital photos are made.
when you look closely enough is actually this:
My Canon 60D, has an 18 megapixel sensor, which translates to 18 million pixels.
As you can see, images from the 60D have 5184 pixels running the longest side of the image, and 3456 running along the shorter side.
When you multiply 5184×3456 you get 17,915,904 pixels, which is rounded to 18 million.
This produces an average file size of 7 MB when using the jpeg file format, which brings us to the question:
How does this relate to file size?
The larger the resolution/more megapixels you have, the bigger the file you’re going to get.
My first digital camera was 3.2 megapixels which produced files around 2 megabytes. The 60D at 18 megapixels averages 7 MB.
This relationship is simple. The more pixels you have, the more data you have, and the more data you have, the bigger the file.
However, the file format you choose also impacts the file size.
How does file format impact this relationship?
Most cameras save images as jpegs by default, but when you snap a photo, the sensor doesn’t just capture the exposure and spit out a jpeg. There’s a whole process to getting that jpeg.
The sensor in the camera doesn’t capture data that we would recognize as a photo. Your camera sensor is like a solar panel, with millions of little solar panels called photo sites. Each photo site represents one pixel.
The photo sites transform light that hits them into electrons, which are then converted to a digital value for the image.
Once the digital values are set, the camera does all kinds of processing to turn that data into a finished image. It applies color, sharpens and saturates the image, and applies settings like white balance to the image. When all of that is done, the camera takes this image that it has created and saves it as a jpeg file, discarding the original sensor data in the process.
Our cameras offer options for saving jpeg files. Some allow you to make all kinds of tweaks to the jpeg processing, but the two we’re most concerned with are quality and size.
Quality refers to the amount of compression applied to the jpeg. The reason jpegs are relatively small is that the image is compressed. Compression is applied using a mathematical algorithm to analyzes the image and discard pixel data that is deemed unnecessary. Typical compression options are:
- Super Fine
When shooting jpeg, I always recommend Super Fine compression. This is the least amount of compression you can apply, resulting in the highest quality image possible. The more compression, the more data is thrown away, and the more data is thrown away, the poorer the quality of your final image. Because this is the point of origin for our images, we want the highest quality image possible.
Then next jpeg option is the resolution. Now that we have 18+ megapixel cameras, we have the option to choose the resolution of the image. Most offer the several resolutions, from full sensor down to 2 or 3 megapixels depending on the camera.
Again, I recommend that you choose the full resolution (largest size) for your image.
There is a caveat. Image resolution is directly related to the maximum print size of the image. For instance, my 18 megapixel camera can print a 12″x18″ image by default.
How you intend to use your image dictates the maximum resolution you actually need. For example, if you never intend to print an image larger than 4″x6″, you only need 2.2 megapixels. For an 8×10 print it’s 7 megapixels.
Despite that, I still recommend you save your images at the highest resolution available. What if five years down the road you want a 12″x18″ print? If you were saving all your files at 2.2 megapixels, you’re out of luck.
It’s important to understand that you can easily take a bigger image and make it smaller, with no impact to quality, but it is much harder to take a smaller image and make it bigger while maintaining quality.
Jpeg options are just one part of the format question. All SLRs and many advanced point and shoot cameras also offer the RAW file format.
RAW is a different kind of image file. Remember all the sensor data the camera uses to generate a jpeg? That’s the RAW file.
With RAW, the sensor data and all the camera settings at the time of the shot are recorded and stored in a file. This gives RAW some amazing advantages over jpeg.
Remember when the camera spits out that jpeg file, all the settings have been applied to the image, essentially fixing the image. Sure you can do some editing in programs like Photoshop, but there are limits to what you can do without degrading image quality.
With RAW, you can go back and actually change all kinds of settings that are fixed in the jpeg image. These changes are made through software provided with your camera, or third party software like Apple’s Aperture or Adobe’s Lightroom. (the Adobe link is an affiliate link)
So with RAW, you can take your image and adjust the exposure, change the contrast, change the white balance, and a whole lot of other things. Here’s a partial list of options I have in Aperture:
White balance (temp and tint)
RAW gives you an amazing amount of power to adjust the final image based on all the sensor data captured, giving you a TON of control over what your final image is going to look like.
There are a couple of downsides to RAW. They are:
- File Size: RAW files are much larger than jpeg files. For example, a full resolution 18 megapixel jpeg is 7 MB compared to the 22 MB RAW file.
- Process time: You can’t just take that RAW file and have it printed, or upload it to the web. You first have to make your adjustments and then generate a jpeg or other image file.
Five or six years ago, those were big drawbacks. These days our computers are powerful enough to make RAW processing super quick, and our memory cards are more than big enough to handle RAW files without any problem.
That does not mean you should shoot in RAW. It also doesn’t mean you shouldn’t shoot in RAW.
There are two schools of thought about this. There are the “Real photographers only shoot RAW” types, and the “RAW is for prissy togs who think they’re better than us.” types.
Neither camp is right. The right answer is to shoot in the format that is best for you. I shot jpeg for about 9 years, and never had a problem with image quality. In fact, I successfully took 8 megapixel jpegs and made 20″x30″ prints that looked AMAZING! Now, WIth Aperture and my new camera, I shoot RAW all the time, and I love the process and control, but if I need files straight out of the camera, I’ll switch to jpeg so I don’t have to process first.
A final note. Many cameras also have the option of shooting RAW & jpeg together. This is nice if you want the RAW data, but want a jpeg for quick access. This is an option I’m not fond of because it gives me one more file to manage, but that’s just me.
So in the end, the answer is simple, and rather complex. To reiterate, in case it got lost in all the gobblydegook, there is no standard, but to future proof your photos you should save them at the highest resolution and quality available, in the file format that works best for you.