Understanding particular exposure

Ya, I was thinking the same thing, except I had disabled 1/3 stop increments for iso when selecting manually, so if I did get out of auto-iso, it would have been set to 100,200,400 etc, not 320.

Hmm, interesting -- in those shots Auto ISO "worked", but not-so-well! The one thing I see is that the one-stop drop from 800 to 400 happened when you actually changed your field of view, so there must have been something that thew the metering off. This is a good reason to chimp whenever you change your position/orientation, and I guess be prepared to override Auto ISO so that in this case you could have gone back to 800.

I don't have Auto ISO, but one thing I do have that can come in handy with a scene like this is Live View used in Exposure Simulation mode. When shooting in ambient light you can "pre-chimp" to check your settings and adjust before taking that first shot from a change in scene.

Hi Corey - I think it was a good idea to take pictures unobtrusively without using flash.

(I have seen it criticised in this thread - in my opinion, unnecessarily)

Hardcore wrote in post #11470330
I will try a better example were all photos were taken at F4. Anyways, I have resigned myself to user error

I killed some of my earlier posts. Got a little carried away when you were sooooooo adamant. Sorry.

Anyway, happens to us all. PP can probably make those shots useable anyway.


Or, we could always go with the national trend these days and blame George W. Bush.

I was totally being stubborn about it so I apologize for that as well.

FWIW Corey, I have seen the exact same thing happen on occasion with my 7D on auto ISO in manual mode. It usually works pretty well but on occasion it does not increase the ISO aggressively enough to properly expose the shot. Now I have pretty much abandoned auto-ISO and just set my ISO manually to obtain the shutter speed, aperture and EC needed to get a properly exposed shot. Essentially the same thing happens in aperture priority or shutter priority. In some situations, not dialing in exposure compensation will result in a poorly exposed picture. In camera metering is pretty good, but far from perfect.

I did learn something on this thread. I had no idea that the 50D had auto ISO. Not that I would ever use it, but it's nice to know.


Time for me to practice what I preach. We have an indoors birthday party tomorrow. The lighting is CFL daylight (which should help with white balanace) bulbs. I'm going to try high ISO with no flash then try lower ISO with flash. I'll shoot high ISO at 1600 to 2500. Flash with 400 to 800.


If I screw it up I officially blame George W. Bush.

philwillmedia wrote in post #11458128
My guess is that the camera metered off the grey table.
That's not far off being 18% grey and it looks pretty well exposed hence the rest of the shot appears under exposed.

From my understanding the picture would actually turn better. Anything close to 14% present gray would make the picture perfect. Literally, i would make the assumption that your WB was wrong.

If i am wrong witch it i could be please let me know as well, i would like to learn something.

Thank.

^we're talking about metering for exposure. White balance and exposure are distinct for the most part.

stop using auto ISO.

If you're shooting manual, shoot manual. I shoot Av with manual ISO and use EC to correct for metering errors, or spot meter a particular area and lock/switch to manual. Some good ol' fashioned chimping for the first few shots would have fixed this all together.

Erik_L wrote in post #11473009
stop using auto ISO.

If you're shooting manual, shoot manual. I shoot Av with manual ISO and use EC to correct for metering errors, or spot meter a particular area and lock/switch to manual. Some good ol' fashioned chimping for the first few shots would have fixed this all together.

This is what I often do - glad to see that I'm not the only one.

Interesting theory about the frequency of the lights. You have to essentially sync your shutter speed w/ the frequency. I can see where the camera would meter when the light output was at a certain level, but when the shot is actually taken, the light is at a different level. But I would see this leading to under-exposing as well as over-exposing (meter when the light is low but have it be higher when the shot is taken).

from how i understand it is less a problem of metering. the meter is right, it doesn't pick up the cycling at all. but when you press the shutter with a value that spans three light cycles (to simplify), then you catch dark-bright-dark and the image is underexposed. or you catch bright-dark-bright, then it's overerexposed.

kendon wrote in post #11473515
from how i understand it is less a problem of metering. the meter is right, it doesn't pick up the cycling at all. but when you press the shutter with a value that spans three light cycles (to simplify), then you catch dark-bright-dark and the image is underexposed. or you catch bright-dark-bright, then it's overerexposed.

The worst problem with gas-discharge lighting and various shutter speeds is when you catch only a PART of a half-cycle. For example, with a shutter speed of 1/250 second you would be capturing the light created by only a half of a half-cycle of the power cycle. A series of shots done at that shutter speed would be all different for exposure and color.

I've encountered this when shooting random pics of my desk/LCD. Seems to depend on the ISO and shutter speed, but it would not be uncommon for half the screen to appear yellow and the rest to look normal.

Easy answer is to just stick on a flash and point it up, or backwards if you're in a small, white room.