G Series: 1 Second Av

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The longest shutter speed available for a Powershot G in Av mode is 1 second.  There, I've said it.  OK, so I'm not 100% sure about this.  The G1 or G2 might be different but my G3, G6, G9 and G12 all have this problem -- or feature, depending on how you look at it -- and I've read enough questions and complaints to feel sure that the G5, G7, G10 and G11 are programmed with the same limit.  The 1 second limit is not a bug because all the G series have it.  Although not a particularly serious problem, the 1 second exposure limit is unexpected -- especially since I typically forget!

Perhaps the 1 second limit is Canon's attempt to save us from ourselves because, of course, we could not hand hold the camera for that duration.  But we also could not hand hold the camera for 1/2 second or, after several coffees, even 1/30 second.  Plus, the little jiggly camera icon comes on to warn us at slow shutter speeds.  Besides, the shutter speed can be set for more than 1 second in Tv or, or course, M modes.  Therefore, I suspect that the 1 second limit is an arbitrary one or perhaps a programming convenience.

The vast majority of the time that the 1 second limit in Av mode becomes a problem to me is when I'm making a High Dynamic Range (HDR) photo.   To make an HDR photo, I typically mount the camera on a tripod, set the lowest ISO, select Av mode and set a mid-range f-stop.  I then use the auto bracketing feature of the camera.  The G series auto bracking can be set for 3 shots at +/- 2 stops.  When the camera is in Av mode, the "stops" are adjusted by changing shutter speed.  As an example, if the "correct" exposure is f5 at 1/60 second then the auto bracketing process produces an underexposed shot at f5, 1/240 and an overexposed shot at f5, 1/15 second.  Most of the time, this works out fine; however, if the base case exposure is, say 1/2 second, then the overexposed shot is at 1 second instead of the expected 2 seconds.  If the base case exposure is at 1 second then the "overexposed" shot is also taken at 1 second which is not useful.

For purposes of bracketing in Tv mode, remember that the (most recent) G series really has only 4 stops of aperture exposure bracketing:  f2.8, f4, f5.6 and f8.  Not all of those apertures are available at all zoom settings.  Also, for purposes of creating an HDR image, variations in aperture produce variations in focus and depth of field.  

As a result of the 1 second exposure limit in Av mode, long exposure HDR sets must be done in manual mode.

Now I can use this post as a reference for anticipated future complaints and explanations.
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G12: Halloween

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I couldn’t resist rigging up the G12 to grab a few Halloween shots. Because of low light (wouldn’t be Halloween otherwise, right?) the pictures would probably show a lot of noise and motion blur but that would be OK. Besides, these were just for fun.

Custom modes are great for saving the setup. I placed the G12 about 10 feet away from the candy hand-off spot, set the widest angle focal length and focused manually. The power saving function was turned off and the display was turned off. The camera was in Av mode at f5.6, ISO 800 and shooting RAW + JPEG. These settings were saved as custom mode C1.

The shot above is seriously cropped (using about 1/4 the full size) from the RAW image and then downrezzed to 800x600.  It was taken at ISO 800, f5.6 and 1 second exposure.  Noise reduction was applied in Adobe Camera Raw (ACR).

Actually, I messed up – or, better said – can make improvements next time with the experience gained. For starters, I should have used Auto ISO and set the maximum ISO at 3200. Sure, the images might be noisy but so what? By using f5.6, the depth of field is from 2.5 feet to infinity when the focus is set for 10 feet. But even at f2.8 the depth of field is from 4.1 feet to infinity! I should have set f2.8 for the low light and set focus at the hyperfocal distance of 7 feet to achieve focus from 3.5 feet to infinity.

Finally, I forgot that the slowest shutter speed for the G series in Av mode is 1 second. This has been a frequent complaint about G series cameras. Of course, no little goblin is going to remain in one place for more than a second anyway so the 1 second limit did not really cost me any pictures.

The G12 was triggered by the Yongnuo RF-602 wireless trigger. Normally used with flash, the RF-602 can also trigger the G12. When fitted to the G12 with the Yongnuo shutter connecting cord LS-02/C1, the RF-602 acts much the same as the Canon wired remote RS60-E3. In addition to its hotshoe connections, the RF-602 transmitter has a button that can be pressed to activate the receiver. It even has the “half pressed” shutter button function!

The G12 battery, an NB-7L clone, easily lasted the setup time plus roughly 75 minutes of being ON without the G12 power saving feature. Of course, the display was OFF. In fact, I’d used the G12 earlier that day for about 15 minutes and then viewed the results of the Halloween shoot for another 15 minutes later that night. I don’t remember how much battery power was left but nothing was blinking.

Too bad I didn’t get a great picture but wait ‘til next year!
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G9: Av and Tv Peculiarities

When the G9 is placed in Aperture Priority mode (Av), the internal logic for selecting the necessary matching shutter speed will not permit shutter speeds longer than one second. If a slower shutter speed is actually required for proper exposure, the LCD will display the “1” in red to indicate that there is a problem. However, the G9 certainly has the ability to use slow shutter speeds.

By using shutter speed priority (Tv), the shutter opening duration can be set for as long as 15 seconds. In Tv mode, if the necessary matching aperture value is not available, then the aperture value that is selected is displayed in red on the LCD.

You may not notice the red aperture or shutter speed display unless you are in the habit of pressing the shutter button halfway and holding it while you check the LCD display.

What are the limiting shutter speeds and apertures of the G9? These limits are usually as: shutter speeds from 15 seconds to 1/2500 second and apertures from F2.8 to F8.0. This is true but some combinations of shutter speed and aperture are not available at all and other combinations are only available under certain conditions.

If you have a G9, you’ve probably already noticed that the aperture range at the full telephoto zoom position is not F2.8 to F8; it is F4.8 to F8. This is a fairly typical characteristic of many zoom lenses and not only Canon products.

Imagine a hole that must be closed. A small hole can be closed more quickly than a large hole. When the G9 is set for an aperture of F2.8, the fastest shutter speed is not 1/2500 second; it is 1/1600 second. In fact, to get a shutter speed of 1/2500 second, the aperture must be nearly F8 if the zoom is at maximum telephoto.

As a means of working around these limits, a “Safety Shift” can be set in the G9 menu. With Safety Shift turned on, the aperture is automatically adjusted, if necessary, even when the G9 is in Av mode. Likewise, with Safety Shift on, the shutter speed will be automatically adjusted, if necessary, even when the G9 is in Tv mode. At first, I didn’t like the idea of the Safety Shift but, more recently, I’ve turned it on. Safety Shift does not affect Manual Exposure mode.

I don’t like the 1 second slow speed limit in Av mode. This has caused me some problems, especially when expecting to get three shots automatically exposure bracketed (AEB) for combining into a High Dynamic Range image. In these cases, I knew that the exposures would be long and had mounted the camera on a tripod. I wanted the same aperture for all three images but, instead of three, got only two different exposures – and sometimes only one! Manual mode is the answer but, unfortunately, auto exposure bracketing does not work in manual mode. This means that the camera must be touched – very carefully! -- between exposures.

These problems, quirks, bugs – whatever you choose to call them -- are not new to the G9. The G3 and, I assume, all the G Series cameras are very similar. As with all cameras, to get the most out of the G9, we have to learn its peculiarities.