Grain and noise issues

Newby

I have been taking pictures with my T2i lately in AUTO Mode without flash in a normally lit room, but the pictures have grain and noise. Pictures do improve a lot once I use flash. Today I was in an aquarium and the flash was not permitted, the pictures looks fine on normal view, but if i start to zoom I can see grain (noise) very obviously. I was using the kit lens EF 18-55mm. Any suggestions for this issue? Thanks.

PBked

Hi @Newby - As you know, exposure involves 3 variables...aperture, shutter speed and ISO. When indoors (even in a fairly bright room) the Auto setting will try to give you a picture by choosing a high ISO with a corresponding low aperture. It is the high ISO that produces the grain.

Try to avoid Auto if possible and experiment with other modes + exposure compensation. One way to do this is to use the CA mode which gives you some control over exposure. Regards, PBked

Newby

Thanks @PBked. I'll do some experiments with the ISO Settings in "P" and "CA" modes.

Moose

Howdy @Newby - Without throwing too much at you, the primary issue is your 18-55mm lens. Think of lenses like glasses of varying shades. Lenses that can obtain low aperture f-numbers (between f/1.2 to f/2.8) are the equivalent to wearing crystal clear glasses. Lenses that can only obtain average aperture f-numbers (between f/3.5 to f/6.3) are the equivalent to wearing dark tinted sun glasses.

Imagine yourself outdoors. With either pair of glasses, you'd be able to see ting clearly thanks to a bright sun. Now imagine walking indoors. It becomes incredibly hard for you to "see" with dark tinted sunglasses.

This is what happens with the T2i when you have a lens like the 18-55mm attached. In order for it to "see" it needs to raise the ISO which increased the image sensors sensitivity to light OR it needs more ambient light. You can get more ambient light by turning on as many lights as possible, opening the shades/curtains, etc... Sometimes that's not enough in a dimly lit room. In those situations, the T2i will try to use the built-in flash to keep the ISO down to a respectable level.

Contrary to what's been said, I would leave your ISO set to Auto whenever your photographing subjects that move or whenever you're hand-holding the T2i in low light. In situations where you're shooting motionless subjects/scenes (cityscape at night), it would be best to manually set the ISO to 100 and mount your T2i to a tripod.

If you try forcing an ISO of 100 (handheld in low light), you're going to end up with more issues than you started with. Things like blur, underexposure, etc...

If you want to reduce the amount of image noise (grain) in your shots (hand-held), the two options are to buy a "brighter" lens (one that can obtain aperture between f/1.2 to f/2.8) or use an external flash. If flash is not permitted, then a "bright" lens will be your only course of action to obtain lower ISO's and to minimize the effects of image noise (grain).

Hope that all makes sense. Happy shooting! :)

PBked

Hi @Moose - I knew you would give Newby some excellent advice. Can I just point out though, that when I mentioned Auto in my reply, I wasn't referring to auto ISO but AUTO mode. I was only suggesting that Newby try out some other modes. Regards, PBked

Moose

Thanks @PBked, yep I was referring to a previous comment by someone else that was a bit confusing...your comment made perfect sense to me. :)