G10 AE lock button (star) to “rough in” exposure

[drcolyn]

Using G10 AE lock button (star) to “rough in” exposure

In the 2009 review by the Backscatter team to find the best point and shoot UW camera the following was written of the G10.

“The Canon G10 quickly won over the staff as the best compact camera on the market.
Our favourite manual control is the (*) button on the back which activates momentary auto exposure. A quick press of this button will rough in your exposure automatically and then return you to manual mode for refinement. These are features we'd like to see on $8000 SLR cameras!”

Has anybody tried out this technique and would you recommend it?
I have tried it only once and quickly decided against using it as I have preset my manual settings (C1 for macro and C2 for wide angle). With my skill level it takes a bit of time reset everything again underwater.
If I sound confused please bear with me as I explain what happens. As said before I have a basic macro setup in C1 mode. Obviously these settings differ (F8 & 1/125 ISO 100) quite a lot from what the camera would have selected otherwise what would be the point of not using the Auto mode in the first place.
So when you press the AE lock (star) button the settings (aperture and shutter speed) are changed so you can see what the camera will use in auto mode.
There is however no way that I can see to return to the C1 mode settings as they were. If one is returned to Manual mode what happens to other settings like white balance and Macro that was selected before pressing the AE lock button.

 

[PNG Diver]

Hello

If I understand your question correctly, there is a simple solution. You are in C1 and have changed the aperature and the shutter speed by pressing the AE lock (*) button. Now you want to return to whatever custom settings you had programmed for C1. Just flick the dial across to C2 and then back to C1 again. This shouldn't take more than half a second. As soon as you return to C1, you will have all of your original custom settings back again. I tried that on my G11 and it worked fine.

Pressing on the AE lock (*) button should not have any effect on your white balance setting or your macro setting.

Hope this helps but I'm not 100% sure that I understand your question.

Regards

Rob

 

[drcolyn]

Hi Rob

OK maybe that was kind of a stupid question but your answer is spot on thanks.
The one time that I did try it I was in manual mode and you can imagine that there was no quick way of reversing that. If I understand you correctly it only changes aperture and shutter speed?

Has this method ever helped you underwater - from experience with a Sony P73 I know that a point and shoot in auto mode will go the easy route: 1/60 F2.8 which is not really where you want to be UW with fish moving all the time. Afterall the camera will not know there is a Z240 strobe waiting to add daylight at the right moment.

Regards
David

 

[PNG Diver]

Yes. It only changes aperture and shutter speed.

I am new to all of this too and it sounds as though you might actually have more experience with underwater photography than I do! But I do have a reasonable understanding of photography on dry land.

The thing to understand when using your nice big external flash is that there are two separate exposures going on at the same time: the ambient light exposure and the flash light exposure. The ambient light exposure is determined by 3 things: 1) the level of ambient light, 2) the aperture size and 3) the shutter speed. The flash exposure is also determined by 3 things: 1) the duration of the very fast flash pulse, 2) the distance from the flash to the subject and 3) the aperture size (but NOT the shutter speed).

Before you press the shutter button, the camera’s metering system is only trying to look at the ambient light level. And there isn’t much light under the water. So if your meter is always defaulting to F2.8 at 1/60, it is because that is the slowest shutter speed and the biggest aperture that the camera will allow WITH THE FLASH TURNED ON. The chances are high that even at those settings, the ambient light will be underexposed. Try turning the flash off and press the AE lock button again to see what the meter really wants to do with the ambient light! (it will give you an even slower shutter speed in a dark environment). When the camera detects low ambient light levels and knows that the flash is on, it basically just gives up on having enough ambient light because it knows that the flash can expose the subject adequately, without having to use a very slow shutter speed. Like you - it wants to avoid a slow shutter speed that might cause blur from the camera or the subject moving while the shutter is open. But - unlike you - it thinks that 1/60 might not be too slow.

If the ambient light is very underexposed then 1/60 might not be too slow - even for a fish that is moving a little bit. The ambient light might just be producing a very underexposed ambient image of the fish - which might be so dark in your photo that you cant even see it when it is overwhelmed by the flash exposure. In contrast, the flash pulse is very fast (around 1/1000th of a second with some flashes) and if that is all that is really exposing the fish, then that may be all that matters. Remember that the flash exposure is not affected by the shutter speed. Ultra high-speed photography of (e.g of bullets flying, glasses shattering or balloons popping) is done with shutter speeds as slow as 1/250 seconds. But the ambient exposure is kept really underexposed. So the only exposure you see in the photograph is the exposure that is due to a very fast flash pulse.

Photography gets really interesting when you begin to separately control the ambient and the flash exposures. In general, your subject will probably be close enough to the flash, that it can be properly exposed by the flash. If everything else that is in the viewfinder frame is also close to the flash, then the flash exposure will dominate and the ambient exposure mightn’t make much difference. But if there is a lot of distant empty water or other distant features in the viewfinder then the ambient exposure will determine the whole effect of the photo - because the flash light might not reach that far. If the ambient light is severely underexposed, then the distant background will all look inky black and a colourful flash-exposed subject will stand out brilliantly against that background. It looks great unless every single photo you take looks like that – when it starts to get a bit boring. If the ambient light is fully exposed, then clear water in the background will have a beautiful blue colour. That might be worth using a slower shutter speed for – especially if your subject is not moving. But your subject might not stand out so well against the lighter background - unless it is a dark subject! Anything else that is in the distance will also get fully exposed by the ambient light and may lead to a cluttered or just ugly background. Unless there happens to be uncluttered and beautiful background elements – which there often is in masterpieces.

Playing with different levels of ambient exposure of the background in all of your flash photographs is a fun way to really come to grips with how your camera works and is worth spending some time with before you go under the water.

If you want more ambient exposure with your flash on in a low ambient light environment, then the only way to do this in Program mode is by increasing the ISO or by using the “slow synchro” mode of the flash. In Av mode, Tv mode or Manual mode, you could also set a slower shutter speed or a larger aperture.

If your main concern is having a fast enough shutter speed to avoid blur, then in Program mode, you could try increasing the ISO or switching the exposure compensation down to -2. In a borderline level of ambient light, then either of these options (or both combined) might lead to a faster shutter speed. But you could also try using the camera in Tv mode and set the shutter speed to 1/160 or 1/200. These options might be easier than manual mode for a beginner because you would retain fully automatic, camera controlled (sTTL) flash exposure - so you would have less to think about.

Also: Be aware of two things: 1) Your Inon strobes may not work well if your shutter speed is faster than the sync speed of the camera. On the G10 and G11, the sync speed is 1/250 secs. So if you go faster than that, your flash exposure may have problems. That is one of the risks if you use Av or Program mode with a higher ISO or in a higher ambient light level. 2) These canon cameras have the stupid and frustrating limitation that their automatic flash exposure metering system (TTL metering) is disabled when the camera is in manual mode. So you will have to use your flashes in manual mode if you use your camera in manual mode.

Not sure if any of this is what you wanted to know. Or even if it is all true but there it is!