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06/17/2007 08:08:41 AM · #1 |
Hello,
I have a Canon Rebel XT. Generally when I shoot, I either use P or Manual modes. However, today I started to play around more with Av. I found out something weird though.
If I shoot with flash, in P mode and let the camera meter, it decides to shoot at 1/60, with f/3.5
However, if I goto Av mode, and set the aperture to f/3.5, it sets the shutter speed to 1.3s and majorly reduces the output of the flash to compensate.
Is there a way in Av mode to force it use more flash to get a higher shutter speed?
Thanks!
Jordan Wilberding |
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06/17/2007 08:34:07 AM · #2 |
From what I understand the camera goes through this sequence in the AV mode.
1. You set the AV
2. The camera adjust the SS accordingly
3. Then the camera adjust the flash to match
I use AV mode the majority of the time unless I'm trying to force something like you indicated. That's when I use the M mode. |
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06/17/2007 08:39:22 AM · #3 |
In the custom menu there is a setting for "Av Mode Flash sync".
Also (at least for a hotshoe) when shooting in Av Mode the Flash (e-TTL) acts as fill flash with generally a weaker output. |
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06/17/2007 09:40:20 AM · #4 |
that 1/60 is a setting that you can change in your menus. It's called min flash sync or something like that. As a general rule, I left mine along. You figure if it defaults to 1/60, you know your ambient is horrible. At that point, you could be shooting at 1/60, 1/200 or 1/1000 for that matter and your flash is doing all the work anyway.
When it would go to 1/60, if I needed to adjust it, I'd just go to manual, because at that point, you should have a pretty good idea of wht you're after anyway.
Now that should be adjustable, but for the most part, I'd recommend leaving it alone. You could always bump your ISO though to allow for a faster shutter and more exposure from the ambient lighting. |
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06/17/2007 10:19:46 AM · #5 |
Thanks for all the replies!
So it sounds like I will just have to shoot in manual mode then. It seems it would be more beneficial to have Av mode act like how I wanted, in case you want to ensure a certain depth of field, and are trying to shoot a scene that requires you to be quick.
Message edited by author 2007-06-17 10:19:54. |
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06/17/2007 10:29:54 AM · #6 |
Originally posted by diginux:
Thanks for all the replies!
So it sounds like I will just have to shoot in manual mode then. It seems it would be more beneficial to have Av mode act like how I wanted, in case you want to ensure a certain depth of field, and are trying to shoot a scene that requires you to be quick. |
The key, with flash, as Dave points out, is that the camera is trying to push the shutter speed around to mix in ambient light, and in this case (where it chooses 1.3 seconds) the ambient light is *so* low that this doesn't make sense.
Using Av mode with flash has little if any benefit that I can think of. If you use M mode, you can still choose aperture, and then *you* choose the proper shutter speed to get the result you want. Flash will adjust power to match the available ambient light, so, adjusting for lower shutter speed will cause the flash to reduce power, and higher shutter speed will raise flash power. The result is that you have control over the mix of ambient light and flash with a flick of the shutter speed knob!
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06/17/2007 11:27:47 AM · #7 |
That is kind of what I figured I would have to do, which isn't a big deal, I was just wondering why Av acted the way it does, but your explanation makes a lot more sense, and it is probably a better way for it to behave than I had wished it would.
Thanks again everyone! |
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06/17/2007 04:58:19 PM · #8 |
Everything you wanted to know about Canon Flash (photonotes.org)
In Av mode, the flash is used as fill and it's exposed for the background.
For me, I use Av and flash for outdoors during the day (making sure to watch the shutter speed to make sure it doesn't go over 1/200 sec). I'll use manual when it gets darker (outdoors at night or indoors). You can control the exposure better with manual.
With manual mode, the flash is used to fill in the needed light. You can drag the shutter or not. |
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06/17/2007 05:16:15 PM · #9 |
You can set the Rebel XT to force 1/200th (max sync speed) in Av mode. But it's only good for fill flash or short distance scenes.
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