f/2.8 vs f/4

I’m trying to understand that difference between the f2.8 and f4 can someone take a picture at f/2.8 then the same picture at f/4 so I can see the difference.

the focal length will need to come into it also. What lens are you asking about? f/4 looks different at 200mm comapred to 35mm.

If you want the shots to compare dof, then Sam is right, focal length will have a big impact on how the shots compare. I think for most, the difference between 2.8 and 4 is one stop of light, which means lower iso and faster shutter.

ChrisBlaze wrote in post #2269069
I’m trying to understand that difference between the f2.8 and f4 can someone take a picture at f/2.8 then the same picture at f/4 so I can see the difference.

1 stop

From the standpoint of exposure value ( or metering) f2.8 lets twice as much light into the lens as f4.0 So if you had an exposure that came out to be 1/125 sec at f2.8, the same "exposure" could be achieved by resetting the camera to 1/60 sec @ f4.0. Since f4.0 allows half the amount of light, the shutter has to stay open twice as long for an equivalent amount of light.

And then there's the concept of depth of field, upon which many books have been published..... - Stu

ChrisBlaze wrote in post #2269069
I’m trying to understand that difference between the f2.8 and f4 can someone take a picture at f/2.8 then the same picture at f/4 so I can see the difference.

70-200mm seems to be the average discussion. I'm looking at the exposure of the two f/stops to see just how much more brighter is f/2.8 compared to f/4.

ChrisBlaze wrote in post #2269120
70-200mm seems to be the average discussion. I'm looking at the exposure of the two f/stops to see just how much more brighter is f/2.8 compared to f/4.

I'm not really sure what you're asking: it lets in twice as much light, which means that you can double your shutter speed. It's one stop brighter.

I know the technical aspects of it, but I'd like to see 2 pictures comparing the 2 in low light.

ChrisBlaze wrote in post #2269136
I know the technical aspects of it, but I'd like to see 2 pictures comparing the 2 in low light.

You probably could not tell the difference between two shots taken with apertures only one stop apart, assuming that shutter speeds didn't get so slow that the shots were ruined by motion blur.

A lens with a larger maximum aperture will always have the advantage of providing you with a brighter viewfinder. That makes manual focussing easier. The larger aperture also will make your auto focus system work a little better in dimmer light.

There will be times when you want to keep the background out of focus. A wider max aperture gives you a little edge over a lens with a smaller max aperture.

The faster lens will allow you to use one stop faster shutter speed when you really need that.

One at 2.8, the other at 4, not changing shutter speed. Note the softness at 2.8.

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rabidcow wrote in post #2269165
One at 2.8, the other at 4, not changing shutter speed. Note the softness at 2.8.

thats windows xp

Hey Rabidcow - What was the shutter speed at F2.8? Could the 'softness' actually be due to camera shake? What lens and focal length is this? And on what camera body? Thanks.

1/100 at 38 mm on a Tamron 28-75 mounted on a 20d. Camera shake is not likely, softness at 2.8 is common regardless of lens, but the Tamron is slightly softer than Canon "L"s at 2.8, but not much.

Gotcha. Thanks for quick the followup. I just wanted to make sure that your shutter speed was OK for the given focal length, and factored for being on a 1.6 crop camera. Your Tamron is pretty sharp at F4.0 though.

chaosbunny wrote in post #2269171
thats windows xp

Are we starting an OS battle here? While we are at it why don't we start an automobile manufacturer battle....