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Why photos are "grainy"

1hornwilly

*Supporting Member III*
I have read a couple threads now on mentions of "grainy" photos. As an amateur (and I mean terrible, but I like it) photographer, I thought I'd explain why this happens to your photos in low light. Who knows, maybe this will be helpful to some of you.

Cameras operate using what's called "the exposure triangle". That triangle refers to shutter speed, ISO, and aperture.

Shutter speed = how fast the shutter opens and closes. Obviously, the longer it is open, the more light it lets in (however, the longer it is open, the more "blur" you get if your subject is in motion.

ISO = sensor light sensitivity. The higher the ISO, the more "grainy" the photo is. ISO 1600 will be much granier than ISO 100. On the old cameras this was referred to as "film speed".

Aperture = The opening created to let light in to the sensor. A lower number will be a bigger opening and let more light in. Sometimes you see if referred to as an F/##. For example, F/2.8 will let in much more light than F/16. The lower the number in this one also means shallower depth of field...like an F2.8 picture of someones face can make the end of your nose in focus and your eyes be blurred. That same pic at F/16 will have your whole face and the person room behind you in clear focus.

So, to get a photo to expose properly you have to give and take from each of these depending on what you want it to look like. To stop a running deer in motion in broad day light you can use a F/16 to get the whole field in focus, shutter speed of 1/500th of a second, and ISO of 100 for the least grainy photo because you have so much light coming in...

That same photo to stop a running deer in motion toward sunset will have to have different settings. It'd be more like F/16 (so you still have all depths in focus), ISO 1600 so you can let more light in, and a fast shutter speed (like 1/250th of a second) so that you can "stop" the deer in the frame.

It's all a give and take. It's why daylight pics can look awesome and dawn and dusk pics before it's to dark to turn on the flash look grainy.

If anyone really cares to hear more about this, I'd be happy to write more. But, that's the basic idea. I bet there are a couple other guys on here that can share some photo stuff too...

Hope this helps explain the "grainy" and I can save a call or two to the camera manufacturer....:smiley_coolpeace:
 

Jackalope

Dignitary Member
Staff member
38,841
260
Thanks a million for posting that bud... I have it in my head from how SP explained it to me. But could never get it on paper.. It's a give an take that every camera company fights..
 

Curran

Senior Member
Supporting Member
7,971
172
Central Ohio
Awesome explanation!!! :smiley_clap:

A good book to look into, that breaks things down enough that even I can understand them is Understanding Exposure by Bryan Peterson. I'm in the process of finishing it now, and it's helped make a big difference with my simple brain being able to make sense of all that stuff!!

Another all around good book is The Digital Photography Book by Scott Kelby
 

hickslawns

Dignitary Member
Supporting Member
39,721
248
Ohio
Thanks for the explanation. Every camera has it's pros and cons. I am learning more every time I swap cards. Throw enough cameras out there and read enough on here, and I might end up figuring out the best way to maximize the pros on the cameras I am using rather than magnifying the cons. rotflmao