ok, so what kinda magic does auto mode have over av mode....

trying to take some low light pics in the house just now of the new kitten running crazy cutting flips......auto mode gives me 1/60th of a second while av mode only gives me like a half second.... totally usless handheld.....hey !! i forgot! ive got a dslr canon xt that has iso 800 and 1600.....wohoo problem solved....not....crank​ed up the iso to 1600, it will still only give me like 1/20th to 1/30th of a second, in the same light that auto mode is handing me 1/60th on every shot at only 400 iso what am i missing here

When you are in Av mode, you must select the aperture - you likely have it set at a small opening (large number). Of course then the meter and computer picks a shutter speed to go with the small aperture, and it picks a slow speed.

Set your f/stop to the widest setting you have (smallest number), and things should work just fine.


Edit: Probably what I should have said is that whatever f/stop you have it set at, that's what the camera will use when in Av mode, and if it's a small aperture, the camera will select a slow shutter speed.

I primarily shoot in Av mode because I almost always do "stills", so I pick an aperture to get the depth of field I desire, and then let the shutter speed fall where it may.

Hope this helps you.

Glenn NK wrote in post #2282345
When you are in Av mode, you must select the aperture - you likely have it set at a small opening (large number). Of course then the meter and computer picks a shutter speed to go with the small aperture, and it picks a slow speed.

Set your f/stop to the widest setting you have (smallest number), and things should work just fine.

............... f 5 on both modes shooting the exact same spot on the wall......auto gives me 1/60th again...... av mode gives me 1/5th a second at 800 iso, 1/25th at 1600 iso.....somebody else try it out inside and see what happens.....any more thoughts ??

nodoubt wrote in post #2282351
............... f 5 on both modes shooting the exact same spot on the wall......auto gives me 1/60th again...... av mode gives me 1/5th a second at 800 iso, 1/25th at 1600 iso.....somebody else try it out inside and see what happens.....any more thoughts ??

Hmmm, very interesting. I selected f5.6 using Av mode and the shutter speed is 1/60. But using P mode, I get f5.6 at 1/90.

Using Tv mode with 1/90, it picks f5.6. So, two out of three modes agree!!

What is going on? I'm baffled.

I have no exposure compensation set.

Help - anyone?

OK, now all three modes agree on mine - this thing is a bit temperamental.

Try it again to see if it has settled down. Your numbers of 1/5 at 800 and 1/25 at 1600 are odd because from 800 to 1600 is only one stop, whereas from 1/5 to 1/25 is about two stops.

Glenn NK wrote in post #2282382
Hmmm, very interesting. I selected f5.6 using Av mode and the shutter speed is 1/60. But using P mode, I get f5.6 at 1/90.

Using Tv mode with 1/90, it picks f5.6. So, two out of three modes agree!!

What is going on? I'm baffled.

I have no exposure compensation set.

Help - anyone?

As there is only a half stop between those three results, the camera will simply be rounding up, or down, from a point somewhere between the two levels. If these are about equidistant from the 'real' setting, wether it rounds up or down will depend on the mode. In practice all three are probably accurate to 1/3 of a stop or closer, which is close enough even for transparency film, never mind digital.

nodoubt wrote in post #2282351
............... f 5 on both modes shooting the exact same spot on the wall......auto gives me 1/60th again...... av mode gives me 1/5th a second at 800 iso, 1/25th at 1600 iso.....somebody else try it out inside and see what happens.....any more thoughts ??

Just a thought on this, and don't quote me because I never use auto so I don't know how it works, I'm just guessing. But could auto have a built in setting to try and keep the shutter speed up to avoid camera shake and be bumping the ISO up. You may have set the ISO to 400 but the auto setting may be bumping it up to avoid camera shake. Although that would involve an ISO of 3200 in theory (although it could be rounding 'the other way').

Try setting the ISO to 400 and take a shot on auto, then check the info to see what ISO it has set.

sandpiper wrote in post #2282428
As there is only a half stop between those three results, the camera will simply be rounding up, or down, from a point somewhere between the two levels. If these are about equidistant from the 'real' setting, wether it rounds up or down will depend on the mode. In practice all three are probably accurate to 1/3 of a stop or closer, which is close enough even for transparency film, never mind digital.

Good point. But what's going on with "nodoubt's" cam?

Learn the connection between ISO, aperture, and shutter. And stop using the green box! Read "Understanding Exposure" by Bryan Peterson. It will shed some light on things.

liza wrote in post #2282470
Learn the connection between ISO, aperture, and shutter. And stop using the green box!

I fully agree with the 'stop using the green box' part, but we do know the connection between ISO, aperture and shutter. That is why we cannot understand why auto is giving f5, 1/60 at 400 iso but Av is giving around f5, 1/30 at 1600 iso. That is a three stop difference in readings pointing at the same subject. This is not a matter of not knowing how they are connected, it is trying to understand what the camera is doing differently to give such different readings.

liza wrote in post #2282470
Learn the connection between ISO, aperture, and shutter. And stop using the green box! Read "Understanding Exposure" by Bryan Peterson. It will shed some light on things.

that advice is well and good and all, but it doesn't explain why his camera is getting different settings between the different modes.

This is precisely why I shoot manual nearly 100% of the time. The camera's metering makes mistakes when left to its own devices.

When you're in Av mode and using the flash, the camera meters for the background and uses the flash as a fill, hence your slow shutter speeds. You have to either use M mode or if you want auto, use P (slightly more advanced auto mode), then the flash and camera just expose for the foreground.

Are your auto shots under exposed? Is the flash popping up automatically when you use auto indoors? Using the camera in auto is essentially using your expensive slr as a P&S camera. When you shoot in Av, you have control over the exposure and you won't need the cheap built in flash (although you may need a tripod). You can get more natural looking shots indoors in Av. Maybe the camera is exposing so dofferently in auto because it is expecting the flash to be used. I don't know, I hardly ever use the flash.

Stefan

liza wrote in post #2282563
This is precisely why I shoot manual nearly 100% of the time. The camera's metering makes mistakes when left to its own devices.

Yes, camera meters can be fooled by strong backlights etc. But they don't normally read the same scene three stops differently, just because you switch mode. That is what this thread is about.

I don't see many Drebel users buying a hand held meter either, to be honest.