Rebel T6 exposure time in aperture priority mode with flash

plantrob

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I just received my new T6, to replace my old Olympus E500 that in sadly dying. I don't have any new lenses yet (was married to a fixed-zoom 50mm lens for my Olympus, I'll have to find an equivalentin the Canon line), but decided to see how I'd do with insect photography with the kit lens. I nearly always shoot in Av mode, so that's what I tried. I was working inside, so I activated the flash, and set F/6.3 as a starting point. Took the photo, and noticed a very long exposure time (1/3s). Tried a few more times, with same result. Then I decided to switch to Macro mode on the automatic dial, and found that a much more reasonable exposure time was selected in this case (1/160s), with about the same aperture (F/5.6) as I had selected, and same ISO (800), and flash automatically activated.

Not surprisingly, on inspection, the Av photos were not only blurry (I'm not that steady) but also overexposed. But I'm confused - why does the camera automatically select an appropriate exposure time in macro mode, but not in Av mode? If I want to use Av mode with flash, how do I get the camera to select a suitable exposure time?
 
I just received my new T6, to replace my old Olympus E500 that in sadly dying. I don't have any new lenses yet (was married to a fixed-zoom 50mm lens for my Olympus, I'll have to find an equivalentin the Canon line), but decided to see how I'd do with insect photography with the kit lens. I nearly always shoot in Av mode, so that's what I tried. I was working inside, so I activated the flash, and set F/6.3 as a starting point. Took the photo, and noticed a very long exposure time (1/3s). Tried a few more times, with same result. Then I decided to switch to Macro mode on the automatic dial, and found that a much more reasonable exposure time was selected in this case (1/160s), with about the same aperture (F/5.6) as I had selected, and same ISO (800), and flash automatically activated.

Not surprisingly, on inspection, the Av photos were not only blurry (I'm not that steady) but also overexposed. But I'm confused - why does the camera automatically select an appropriate exposure time in macro mode, but not in Av mode? If I want to use Av mode with flash, how do I get the camera to select a suitable exposure time?
Short answers:

1) Canon will expose for 'background' in Av mode and assume flash is "fill-flash", ie not the main illuminator

2) If you want the flash to be the main illuminator then set to manual mode with Shutter speed no faster than 1/200, aperture to suit DOF and let the flash work itself out. Slow down the shutter and/or increase the ISO if you want a more natural background

Longer answers:

Read the manual

Read https://www.dpreview.com/articles/1905744226/rebel-forum-faq and in particular "I can't get flash to do what I want"

Go to Canon's Digital Learning Centre to get the best out of your new camera
 
Last edited:
Following on to what AnthonyL said...

When you select Av mode, you're telling the camera, "I'll set the aperture but I don't care what shutter speed is used." When Av mode is used with flash, it's how you get fill flash (sometimes called slow-sync). From page 112 of the manual (the section on Av mode):
In low light, the subject is exposed with the auto flash metering, and the background is exposed with a slow shutter speed set automatically. Both the subject and background look properly exposed with a touch of atmosphere (automatic slow-speed flash sync). If you are handholding the camera, keep it steady to prevent camera shake. Using a tripod is recommended.
Whenever you care about both aperture and shutter speed, that's what M mode is for. Set up your M mode with a shutter speed of 1/200, then use whatever aperture you want along with flash. Using slower shutter speeds gives more background.

Or if you don't care that much about either aperture and shutter speed, and just want a nice flash picture, there's P mode.

This is how it works on every camera model I know of (that offers Av or A mode). Fill flash is a powerful tool, so much so that many people pay considerably more to get a flash that supports high-speed sync (HSS) so that they can use fill-flash in full daylight without having to stop their lenses way down.

That said...

Long ago, Canon decided to accommodate those photographers who had no use for fill flash, and instead wanted to leave their cameras in Av mode when using flash. Check page 261 of your manual for Custom Function 3.
 
Following on to what AnthonyL said...

When you select Av mode, you're telling the camera, "I'll set the aperture but I don't care what shutter speed is used." When Av mode is used with flash, it's how you get fill flash (sometimes called slow-sync). From page 112 of the manual (the section on Av mode):
In low light, the subject is exposed with the auto flash metering, and the background is exposed with a slow shutter speed set automatically. Both the subject and background look properly exposed with a touch of atmosphere (automatic slow-speed flash sync). If you are handholding the camera, keep it steady to prevent camera shake. Using a tripod is recommended.
Whenever you care about both aperture and shutter speed, that's what M mode is for. Set up your M mode with a shutter speed of 1/200, then use whatever aperture you want along with flash. Using slower shutter speeds gives more background.

Or if you don't care that much about either aperture and shutter speed, and just want a nice flash picture, there's P mode.

This is how it works on every camera model I know of (that offers Av or A mode). Fill flash is a powerful tool, so much so that many people pay considerably more to get a flash that supports high-speed sync (HSS) so that they can use fill-flash in full daylight without having to stop their lenses way down.

That said...

Long ago, Canon decided to accommodate those photographers who had no use for fill flash, and instead wanted to leave their cameras in Av mode when using flash. Check page 261 of your manual for Custom Function 3.
Following on to what AnthonyL and Doug said...

Remember that you can usually set some sort of FEC (Flash Exposure Compensation) to adjust the flash's output too.

For macros though, I'm always in full Manual exposure mode, as well as full manual flash power mode for max consistency.

R2

ps. next...
 
Thanks for your answers. The manual must have changed quite a bit, because mine has much fewer pages than the page number quoted above, and has no information at all pertaining to this question (I did read the manual before posting :-)).

I understand what's going on - it's just very different from my Olympus experience, where shutter time was automatically adjusted down when I used flash. Since my attempts at insect photography are often quite time-bound (only until it flies away), and unpredictable (I often come across a subject while doing flower photography) it was convenient to just be able to hit the flash button and start shooting - I learned that using flash really helped getting a nice crisp close-up, even in good ambient light conditions. For flowers and most other subjects, I think I'll continue to use Av (and no flash), so this means I'll have to fiddle with controls more before I can start taking pictures. I guess I'll just have to get good at that...
 
The manual must have changed quite a bit, because mine has much fewer pages than the page number quoted above, and has no information at all pertaining to this question

[For those not familiar, that "c-wss.com" domain looks a bit questionable. It's the usual domain for official Canon US documents. If it makes you more comfortable, you can get to the same place via links from https://www.usa.canon.com/internet/portal/us/home/support/camera-user-manual]
 
Thanks! I downloaded that much more extensive manual, and will take a closer look. I think I'll go with the custom flash sync setting, given how I tend to use my camera (I don't much care about background when using flash)
 
The manual must have changed quite a bit, because mine has much fewer pages than the page number quoted above, and has no information at all pertaining to this question
http://gdlp01.c-wss.com/gds/8/0300022698/01/eos-rebelt6-1300d-im-en.pdf

[For those not familiar, that "c-wss.com" domain looks a bit questionable. It's the usual domain for official Canon US documents. If it makes you more comfortable, you can get to the same place via links from https://www.usa.canon.com/internet/portal/us/home/support/camera-user-manual]
That domain is safe Doug.I've used it for all Canon manuals etc without issue.
 
The manual must have changed quite a bit, because mine has much fewer pages than the page number quoted above, and has no information at all pertaining to this question
http://gdlp01.c-wss.com/gds/8/0300022698/01/eos-rebelt6-1300d-im-en.pdf

[For those not familiar, that "c-wss.com" domain looks a bit questionable. It's the usual domain for official Canon US documents. If it makes you more comfortable, you can get to the same place via links from https://www.usa.canon.com/internet/portal/us/home/support/camera-user-manual]
That domain is safe Doug.I've used it for all Canon manuals etc without issue.
But why even go to an unfamiliar domain when the official site has the manuals? Even if the site is an official Japanese Canon site.

Best start at https://www.usa.canon.com/internet/portal/us/home/support/user-manual-library and work your way down or a Canon site in your region https://global.canon/en/support/ where also other software, documentation etc is available for a specified Camera and Operating system.
 
The manual must have changed quite a bit, because mine has much fewer pages than the page number quoted above, and has no information at all pertaining to this question
http://gdlp01.c-wss.com/gds/8/0300022698/01/eos-rebelt6-1300d-im-en.pdf

[For those not familiar, that "c-wss.com" domain looks a bit questionable. It's the usual domain for official Canon US documents. If it makes you more comfortable, you can get to the same place via links from https://www.usa.canon.com/internet/portal/us/home/support/camera-user-manual]
That domain is safe Doug.I've used it for all Canon manuals etc without issue.
But why even go to an unfamiliar domain when the official site has the manuals? Even if the site is an official Japanese Canon site.

Best start at https://www.usa.canon.com/internet/portal/us/home/support/user-manual-library and work your way down or a Canon site in your region https://global.canon/en/support/ where also other software, documentation etc is available for a specified Camera and Operating system.
It's not unfamiliar to me been using it for years.When I do a search for a manual it's the first thing that comes up and I get directed straight to the manual with one click. I haven't had a virus or malware on my computers for longer than I care to remember.
 

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