Aperture priority and speedlites

[Joselito]

I would sometimes resort to using flash mounted on the camera in low light. As I would like to control my DOF I will put it in aperture priority. However what happens is the the shutter speed tends to be slow and thus I end up with a motion blur on my images. So when using flash what would be better? Shutter priority or merely switch to manual. My speedlite is a canon on ETTL and camera is also a canon. Is there an adjustment or setting that I need to set when using flash and aperture priority? Or this is an impossible combination in low light and movement of subject is a problem? I would appreciate your comments on this.

Joselito

[Shadowman]

Joselito,

What aperture did you set the camera to?

[Mike Buckley]

I'm far from a speedlight expert but the two methods shown below used on my Nikon system work for me. I am welcome to any ideas that would be worth considering.

Method 1
Camera set to Aperture Priority and the aperture set to render the desired depth of field
Auto ISO disabled
ISO set to base ISO unless I want a short recycling time for the speedlight
Camera's built-in flash set to TTL mode
Speedlight set to TTL mode
Speedlight's exposure compensation set to render the desired histogram

Method 2 -- Same as Method 1 except:
Camera set to Manual exposure mode and the shutter set to 1/60

[DanK]

Joselito,

You will have to check your manual, but I believe that many Canon cameras expose for ambient light when you use flash in combination with aperture priority. The solution, as you suggest, is to use manual or shutter priority. If you have sufficient flash power and an ETTL flash, it is simple to use manual mode because the camera will meter the light produced by the flash. For indoor shots, I often will set the camera to 1/60 and f/4 or so and let the ETTL system control the flash output to get the right exposure.

Dan

[PhotomanJohn]

Joselito,

If you are in low light and your subject is moving you will generally have issues unless you get the shutter speed up high enough that the ambient light doesn't significantly contribute to the exposure. I would suggest using manual mode and a high enough shutter speed (like 1/125), leaving the flash in auto and using an aperture with-in the exposure capabilities of your flash for the given situation. The camera will adjust the flash output for you and you can use flash exposure compensation if needed. Use the ISO setting to help out if the flash doesn't have enough output to give you a proper exposure.

John

[inkista]

Canon cameras assume you want fill flash no matter what in Av/Tv. So, the exposure will be set close to ambient, and only a small amount of flash will be sent out to "fill in" the shadows. In P, it does this until lower light levels, at which point it switches to using flash as main illumination, like a P&S camera would. In M, you can balance the flash against the ambient however you want.

So, first easy answer: set the camera into P in low light.

You can still shoot in Av with a heavier balance to the flash in low light, if you mess with your custom functions. There's a setting in there to limit your shutter speed while you're in Av mode and shooting with flash. Set it to be your x-sync speed, or in the 1/60 to x-sync speed (depending on which camera body you've got), and the flash will behave in Av the way it does in P.

This Strobist article and this Tangents post both discuss balancing the flash against the ambient if you want to go full Manual and learn how to do this with more fine-grained control. The Tangents blog is probably a better resource if you want to learn how to use on-camera flash, eTTL, and bouncing. Strobist is better if you want to learn how to do off-camera studio-style lighting.

[JR1]

Have I missed something I can't see a reference to what make of gear you have, yes Canon but what

THIS is the best site

I often use flash at 1/500, 1/1000th it is HSS

http://photonotes.org/articles/eos-flash/index.html

[Geoff F]

Try this, Joselito, it is what I do.

Set your camera manually to suit the scene (aperture and shutter speed) plus choose a suitable Iso.

Use the flash in ETTL mode; but remember that some flash output compensation may be needed. That is a case of experimentation.

You can use a shutter speed up to 1/250 (depending on your equipment) or select high speed flash for faster shutter speeds; but coverage may be reduced in that mode.

When I first got a 'proper' modern external flash with variable output, I was working as though I still had an old fashioned fixed output unit and was getting nowhere, like you describe. But once I started working as I have outlined, everything fell into place and now works fine for me.

[inkista]

... THIS is the best site ...

http://photonotes.org/articles/eos-flash/index.html

Ummm. Respectfully disagree. It is a great site. Particularly if you are into collecting vintage flashes , need to know about vintage gear, film-camera compatibility with flash, and the evolution of the Canon flash line. But there is a ton of historical information in there that's not relevant to digital shooters; and there's not very much "how to" information. And if you print it all out it's something like 140 pages. It is an older document that has not been updated to include the new RT equipment (600EX-RT, ST-E3-RT). It is one massive infodump, and useful as an infodump, but not as a tutorial.

I'd actually point to Syl Arena's Speedliter's Handbook as the go-to resource for learning the basics of using flash with Canon gear, and the so-called "EOS Flash Bible" as a reference after you've learned the basics.

[shreds]

Simple....just go manual then you are in control......

[dan marchant]

Agree with the above. Aperture Priority the flash automatically assumes that you want fill flash and this can result in a low shutter speed. Switch to manual, set the shutter to something like 160th and the flash in ETTL.

[Joselito]

Usually at 5.6

[Colin Southern]

Ummm. Respectfully disagree. It is a great site. Particularly if you are into collecting vintage flashes , need to know about vintage gear, film-camera compatibility with flash, and the evolution of the Canon flash line. But there is a ton of historical information in there that's not relevant to digital shooters; and there's not very much "how to" information. And if you print it all out it's something like 140 pages. It is an older document that has not been updated to include the new RT equipment (600EX-RT, ST-E3-RT). It is one massive infodump, and useful as an infodump, but not as a tutorial.

I'd actually point to Syl Arena's Speedliter's Handbook as the go-to resource for learning the basics of using flash with Canon gear, and the so-called "EOS Flash Bible" as a reference after you've learned the basics.

NK "updated" the photonotes article by way of an excellent book:

http://www.amazon.com/Mastering-Cano...eywords=nk+guy

Full Disclosure: The author was kind enough to send me a printed copy at no charge.

[Joselito]

Thank you all for your explanations and suggestions. Now I think I understand what is happening in those situations.

John, I usually set the aperture somewhere at 5.6 or 4.

Jeremy, I use a 60 D canon and an EX 600rt speedlite.

I think i will adopt the majority suggestion to go manual bearing in mind Geoff's comment that there can be some experimentation on this.

Again thank you to all for helping out

[Colin Southern]

Joselito,

To address the original question ...

The camera considers the scene to be divided into two regions when using a flash (just think of them as "foreground" and "background"). It does this by metering the ambient light in all AE zones and then again when firing the pre-flash; zones that don't change significantly are deemed to be "background" and those that do respond to the preflash are deemed to be "foreground".

In Av mode the camera will raise or lower the shutterspeed at the selected ISO to obtain a standard exposure of the BACKGROUND zone, and add flash light to obtain a standard exposure of the FOREGROUND zone (usually just fill flash as Kathy mentioned).

You can bias these settings using EC and FEC (Exposure Compensation and Flash Exposure Compensation) or you can over-ride them completely any use manual exposure (and manual flash exposure too if you want). There's no such thing as a "free lunch" though; sure, you can raise the shutterspeed at any given aperture as high as you like, but the consequence of that will be a grossly under-exposed background.

Bottom line is that cameras require light to record - so you either have to provide that light yourself - tell the camera to work with less light (by raising the ISO) - or keeping the shutter open longer. Each solution has advantages and disadvantages. If you're in a situation where subject motion and/or camera shake are an issue then usually the best option is a combination of higher ISO - wider aperture - and moderate shutterspeeds. Flash - generally - freezes motion reasonably well, but how much movement shows up in background areas will depend on the level of exposure (eg if I was taking a 45 minute exposure then you could stand in front of the camera for a minute or two without affecting anything).

Hope this helps.

[JR1]

Ummm. Respectfully disagree. It is a great site. Particularly if you are into collecting vintage flashes , need to know about vintage gear, film-camera compatibility with flash, and the evolution of the Canon flash line. But there is a ton of historical information in there that's not relevant to digital shooters; and there's not very much "how to" information. And if you print it all out it's something like 140 pages. It is an older document that has not been updated to include the new RT equipment (600EX-RT, ST-E3-RT). It is one massive infodump, and useful as an infodump, but not as a tutorial.

I'd actually point to Syl Arena's Speedliter's Handbook as the go-to resource for learning the basics of using flash with Canon gear, and the so-called "EOS Flash Bible" as a reference after you've learned the basics.

I also agree, but it is one of the best I have found online to date, personally I would simply google youtube....flash....tutorials

There are hundreds

http://www.youtube.com/watch?v=viiYhcFyq4E

I have the SB910 Nikon, both the canon you have and mine are top models you could not wish for better

[Joselito]

Thank you Collin. The EC and FEC are adjustments that I really have to explore and learn how to use properly. I seldom touch EC more so the FEC.



Joselito

[Colin Southern]

Thank you Collin. The EC and FEC are adjustments that I really have to explore and learn how to use properly. I seldom touch EC more so the FEC.



Joselito

You're welcome. As a starting point, dial in -1 EC and -2/3 FEC and go from there for most situations outdoors (the -1 adds saturation to the sky and the -2/3 stops the "over-flashed" look). Flash metering with the 600EX-RT is deadly accurate (I've got 6 of them).

[Joselito]

Wow 6!!! I can just wish! Just to be clear Collin. Adjusting EC and FEC in AV mode, right?

[loosecanon]

There is a custom setting that controls the behaviour in AV. As you have it it is in the default where the camera will attempt to balance the flash and ambient light . Other settings are fixed maximum sync speed eg. 250th second, or no lower than 60th second. Set up one of the Custom modes as AV with the custom speed setting, then you can turn to this whenever you wish flash with higher sync speed.