Basically this function increases your ISO settings in order for your chip to gain more information with less available light.
NOTE: This is a DIGITAL function done on the CHIP / processor of your camera. NOT in the lens of your camera.
This function should not be compared to, or confused with the Cannon (OPTICAL) IS, or Nikon VR (Vibration reduction) or any other LENS term. It functions, acts and has a completely different effect on your images!
I first came across a client who had been doing her own product photography and had to ask what she was taking images with that was causing them to be so grainy (ok yes, digital people grainy is a film term for the "digital noise" you get on the chip.. I'm from the old school of film.. it shows sometimes).
She told me the camera that she was using... and I had to probe a little more... no way that camera was in the right mode and kicking out these images! She told me that she used the DIS mode, because someone said it would keep her images from being blurry.
OH STOP THE PRESS!
I mean... SHUT THE FRONT DOOR (see I can be hip, lol)
They said WHAT!?
No no... let me tell you what really goes on.
The elements of an exposure:
Your camera is like your head, right?
The eyelid is your shutter it "blinks" or opens and closes to control HOW LONG the "frame" or image is exposed for.
Your iris is your Aputure: it dilates or contracts allowing for HOW MUCH light will be let in.
The Brain is like the chip. It has to decipher the code. You can also set the SENSITIVITY of the chip (ISO) so it can "remember" or "capture" more information.
Note: These 3 things control your exposure. FOCUS is controlled by your LENS.
Which is what this "DIGITAL" IS mode is doing. It is increasing the sensitivity to light so your camera can capture more information. This however, does come at a price. Just like in film days.. when you had to learn the differences in film speed... its the SAME concept.... they didn't even change the term when they made it digital! Lucky us!
So remember your film speeds... 100 - for BRIGHT sun, then you increased the speed according to each lower light, or faster action that you planned on shooting.... so 800 was good for inside low light, or sports... but when you got it printed it looked green and had little dots all over it, and it looked worse the larger you printed them? That was the FILM grain. Because in order to make film more sensitive to light they made the pieces that the light reflected off of (the grain) larger... so you saw it when you printed it... because you basically put it under a microscope to make a 4x6 version.
Ok... so how does this history lesson apply... take everything I just said, and change the word film, with digital... and grain with noise.
Instead of the pieces physically increasing in size they become more "sensitive" to light electronically... but the result is the same, only with better color balance. You see spots on the image which make it appear MORE broken and that "could" be described as blurry... but its not, its noisy because your seeing the pixels braking down in the image. sensitivity was turned up. If your sensitivity is turned up, things don't look clear... so don't do it when you need quality clear images!
Now.... DIS has its place, just like 800 speed film... and that place is LOW light NO flash venues... like concerts, parties... things like that. Places where you need it to be more sensitive, because of the low light, no flash, and no tripod... but your not trying to sell an item, your trying to capture a moment. It's like.. the last resort option to get any sort of workable image.
NOT for product photography.
If your images are blurry from camera shake (which is the most likely suspect, and the reason this DIS mode would have been suggested at all) during your product photography sessions- you have WAY to little light on it! Instead of adjusting by controlling your ISO, which may increase the sensitivity, but adds grain/noise to your image, consider shooting during the day, or outside, or with a tripod so you can leave your shutter open longer, adjust your shutter speed, or aperture... or in just about any way...INCREASE your light... or QUALITY of light. This means less grain / noise and less distractions to your image.
I am happy to report, that my client took my advice and now even the images she has to do herself are turning out more clearly and with some practice and other tips her backgrounds are getting more and more white - and the focus is become more and more on her products! I LOVE that she continues to improve and her shop is better for it!
If you are stumped by a photography situation, want me to troubleshoot and tell you what is going on or how you can take better images - Please just ask! I love to see you succeed!