G9 Fill Flash

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Continuing with the G9 flash fixation, this post is about fill flash. Although previous posts are labeled as flash and exposure compensation, fill flash is, in a way, much the same sort of thing.

First, I set up a very contrasty scene featuring the lovely Hannah . A similar situation – although perhaps not as drastic – occurs when an expanse of sky is included in a scene. The G9 was simply placed in Program Mode (P), ISO 80, widest angle, small Flexizone auto focus and evaluative metering. (For uniform comparisons, all pictures herein are the in-camera JPEG.) Poor Hannah! Although she enjoyed the shade and was not squinting at all, the bright concrete driveway convinced the G9 metering system to use 1/1000 sec and f4 to avoid overexposing the scene. What to do?

Fill flash is the answer here. The question is “How much fill flash?”. Rather than deal with theory, classic ratios, etc., I simply turned on the flash and took another shot. Not too bad! On close examination, several interesting changes took place inside the mind of the G9 (remember it was still in Program Mode, etc. but the flash was turned on). First, the exposure settings were changed to 1/500 second at f5.6; those who follow such details (and all aspiring photographers should) will recognize that these settings produce exactly the same exposure as 1/1000 second at f4. This change was made because the G9 limits its little built-in flash to 1/500 second and at 1/500 second the proper aperture was f5.6. Next, the G9 flash pre-flashes to check the effect and then fires at what it thinks is the necessary power. On second thought, Hannah is actually a bit underexposed. More power is needed.

It turns out that the flash picture was taken with the Slow Sync setting turned OFF so I changed to Slow Sync ON. Duh! Same exposure settings and same result. Next I changed to Aperture Priority (Av) mode and set the aperture at f5.6 to avoid confusing myself. Same results. How about Shutter Priority (Tv) at 1/500 second? Same. Not to be denied my right to force my preferences on the G9, I changed to Manual exposure and kept 1/500 second and f5.6 but forced full power to the flash. (Remember that manual exposure mode also means manual flash adjustments.) Same results – that’s when I realized that the little built-in flash was maxed out. With the flash already firing at full power, there would be no point to increasing the flash compensation setting. So ISO 80, f5.6 and a camera to subject distance of about ten feet is about the limit for the G9. (This would be a Guide Number of 56 but I suspect the GN is really about 40.) Time for a bigger gun.

Next, a Canon 420EX was placed directly on the G9. Again, the G9 was put into P mode. The result was definitely an improvement over the built-in flash. Again, several interesting changes were made by the G9 (not by me). The shutter speed was changed to 1/250 second because that is the limit of external flash unless the external flash can handle “High Speed Sync”. At 1/250 second, the correct aperture setting (considering that bright background) is f8. Actually, the G9 did not particularly like either the 1/250 or the f8 and indicated so by showing both in red on the display. Another point of interest is that the color balance was changed when using the 420EX. The G9 was set for automatic white balance so this was an internal decision by the G9.

The Canon 420EX accomplishes High Speed Sync on the G9 by pulsing rapidly. Unfortunately, this means that flash power is reduced for each pulse. Does the 420EX have enough power at High Speed Sync? I switched the 420EX to HSS and fired away. The G9 responded by changing to 1/1000 second at f4 and the 420EX pulsed away (not noticeable to me). As shown here, the 420EX really does not have quite the necessary power but is close. Also, f4 nicely blurred the background as compared to f8.

Last, I replaced the 420EX with a Nikon SB-28. The SB-28 fires from the G9 but the flash power must be set manually and on the flash. The advantage to using the “incompatible” SB-28 on the G9 is that the G9 ignorantly operates at shutter speeds up to 1/2500 second! Realizing that the “correct” ambient exposure was 1/500 at f5.6, I intentionally set the G9 at 1/1000 second and f5.6 to make the background slightly underexposed. The best setting for the SB-28 was at half power which produced this shot. It’s OK, although the color balance is a bit cool.

Conclusions? Well, fill flash can be very useful and is essentially for some situations. The G9 flash is a bit weak but is certainly convenient. The limits on flash power, sync speed and aperture can lead to false conclusions so be aware of those limits. I much prefer external flash (in fact, off-camera flash). The most understandable setup for me is the G9 in manual mode with the SB-28 also in manual mode; however, this setup often requires a bit of tinkering and trial shots – but I’ll get better at it with practice!
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G9: Exposure and Flash Compensation in Tv Mode

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The previous posts showed the effects of combinations of exposure and flash compensation on a typical indoor scene with the G9 using its built-in flash and operating in Program (P) mode and in Aperture Priority (Av) mode. This post is similar but is about shutter speed (Tv) mode and flash. I selected a shutter speed of 1/30 second simply because so many other photos were taken at 1/60 second. The setting and lighting was similar to the previous posts; however, these pictures were taken on a different day.

In Tv mode, the photographer manually sets the shutter speed and the G9 selects the aperture to give the “correct” exposure (according to the G9). Simple enough, but there are a few peculiarities and precautions. In Tv mode, because the shutter speed is selected by the photographer, there is no “Slow Sync” and the G9’s choice for aperture is based on ambient light. However, in low light situations, if the flash is turned on and the aperture is at maximum then the ambient exposure is essentially “locked”. This means that exposure compensation is actually rendered inactive when the flash is turned on if the G9 is in Tv mode in low light situations. Figure 5 (continuing the numbering from the previous post) illustrates this limitation at the 0 and +2 exposure compensation settings.

A peculiarity is that, with the G9 in Tv mode, if the flash is not turned on, and if “Safety Shift” is turned on (menu selection) then the shutter speed selection might be changed if the aperture cannot be further increased. This is shown in Figure 5 by the middle picture in the top row (no flash, 0 exposure compensation). The shutter speed that I selected was actually 1/30 second but the G9 wanted an aperture larger than f2.8. Since that larger aperture was not available, the G9 safety shifted to 1/20 second. (OK, so I forgot Safety Shift was turned on! I usually shoot in Av mode and find Safety Shift useful in that mode.)

Figure 5

Because shutter speed and aperture were the same for both 0 and +2 exposure compensation, those pictures using flash are also the same. Now, take a close look at the picture based on FC=0 and EC = -2. That picture is only slightly darker than the FC=0 and EC=0 picture. It almost looks like the flash is compensating for negative exposure compensation but I’ve been saying that flash compensation and exposure compensation are independent. What’s going on here?

Because electronic flash (yes, there are other technologies) has such a short duration – about 1/1000 second give or take – the light detected by the sensor/film is relatively independent of shutter speed. It is the aperture that governs exposure from flash. For this series of photos, the shutter speed was set at 1/30 second. To achieve exposure compensation, the G9 changed the aperture. For example, an exposure compensation of -2 was obtained by changing the aperture from f2.8 to f4.5 (and shutter speed from 1/20 Safety Shifted to 1/30). The G9, realizing that the aperture was f4.5 and not f2.8, fired the flash more powerfully. I have to admit, begrudgingly, that the G9 somewhat “compensated” for exposure compensation in this case; however, I really maintain that the G9 flash power was actually based on aperture and not exposure as the combination of shutter speed and aperture. In any case, certainly FC=0 and EC= -2 (sum = -2) does not produce the same result as FC= -2 and EC=0 (sum = -2).

After these experiments with exposure compensation and flash compensation in P, Av and Tv modes, it is easier to understand how G9ers (and G10ers – probably all Powershot users) can become confused about flash photography. For starters, there are definite limits on available shutter speeds, apertures and even flash power. There is a Safety Shift in both Tv and Av modes but Safety Shift does not work when the flash is turned on. For P and Av modes, there is a Slow Sync option. Flash exposure is largely based on aperture and not shutter speed. Flash and exposure compensations are truly adjustments based on the normal logic of the G9. Finally, even though somewhat counter intuitive, flash compensation and exposure compensation are independent.
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Sky Too Bright?

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Bright sky and dark foreground are not a happy combination for photographers unless both can be captured. This difficulty is not unique to digital photography. Although sometimes the available dynamic range of the digital camera (or film) is inadequate, often the light meter is simply fooled. The three photos above illustrate this problem. All photos were taken within a short time (but the clouds were moving quickly) with my G9 mounted on a tripod, evaluative metering, Av mode at f5.6, ISO 80 and shooting raw + jpg. The photos above were downsized from the in-camera jpg and sharpened for web viewing (PK Sharpener ) but are otherwise unprocessed.

For the bright sky problem, the hoped-for-solution is the “correct” exposure. Think about a bright sky scene from the point of view of the exposure meter. If there is only a little sky, then the exposure is based on the ground – 1/160 sec in Photo #1 above. If the composition is mostly sky, the exposure meter thinks there is a lot of available light – 1/640 sec in Photo #2. As the camera operator, uh, photographer, you might manually set an in-between exposure value. Some metering systems attempt to do this automatically; Photo #3 was taken at 1/320 sec as determined automatically by the G9. So Photo #1 has good ground but no sky detail; Photo #2 has a beautiful sky but dark ground; Photo #3 is sort of a blah in-between.

While taking photos 1, 2 and 3 above, the live histogram of the G9 indicated that Photo 1 was overexposed –a little more than a full f-stop. Photo 2 was slightly underexposed – about a half stop. Photo 3 is slightly overexposed – perhaps a half stop. So the “best” exposure would have been about f5.6 and 1/400 sec manual exposure (not very far off Sunny 16 for the G9) or by dialing in a -2/3 exposure compensation for Av mode. I didn’t get a shot at f5.6 and 1/400; however, I was shooting with +/- 1 auto exposure bracketing so I’m pretty sure of those relative effects.

I was interested in comparing the in-camera jpgs for normal, graduated neutral density filter and a polarizing filter; these photos are shown below (Photo 3 is repeated). Again, all photos were taken in Av mode using evaluative metering without exposure compensation.

In Photo #4, the 50/50 split, graduated neutral density filter (Tiffen ND 0.6) performed as expected but the upper clouds were darkened excessively. At 1/250 sec, it is slightly underexposed – perhaps 1/3 stop. Photo #5 shows the effects of a polarizing filter (Tiffen Circular). The filter was rotated for maximum sky detail. Unlike my G3, the effects of rotating the polarizing filter could be seen in the G9 LCD display. At 1/160 sec, the polarized exposure is just about right according to the histogram.

Nest is a comparison of raw and jpg; shooting in raw + jpg mode allowed a direct comparison. The third set of photos (below) compares Photo 3 (the in-camera jpg from the first and second sets) to the processed raw version, Photo 6. Similarly, Photo 7 is the raw version of Photo 5.

Both raw files (6 and 7) were processed in Adobe Camera Raw using the same settings. Surprisingly, no exposure adjustment was needed -- even though I’d previously noted that Photo 3 was slightly overexposed. The “Recovery” adjustment compensated for this highlight recovery. The ACR settings for Photo 6 and 7 were:

WB: Daylight
Exposure adjustment: 0
Recovery: 15
Fill: 10
Black: 8
Brightness: 40
Contrast: 0
Clarity: 40
Vibrance: 8
Saturation: 3
A “Medium Contrast Curve”
Sharpening: 80
Radius: 0.8
Detail: 30
Masking: 0
Luminance Noise Reduction: 0
Color Noise Reduction: 25

All other ACR settings were at zero. After opening in ACR, “Smart Sharpening” at 100 was applied in Photoshop CS3. No other post processing was applied.

In retrospect, I should have applied a bit more saturation to Photos 6 and 7 just for purposes of comparison to Photo 3 because Canon’s in-camera jpgs are a bit saturated (some say over-saturated).

Lessons learned? Well, I’ll continue to shoot in raw and will be using my polarizing filter more often.

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G9 and Sunny 16

My first camera, a Kodak Brownie, had no exposure controls. Years later, I had a fully manual camera with exposure controls but no light meter was included or needed. Instead of using a light meter, I simply followed the instructions included with every box of film. These instructions were the recommended camera settings for sunny or cloudy days, light shade, heavy shade, etc. Books and magazines also provided recommended exposures for various indoor and outdoor lighting scenes. Such exposure guides are still valid and useful.

A very useful point of reference for exposure is called the “Sunny 16 Rule”. The rule is that on sunny days where shadows are distinct, a correct exposure is f16 aperture when the shutter speed is set at 1/ISO second. For example, suppose the film (or digital sensor) has an ISO rating of 100. In bright sun, a correct exposure would be f16 at 1/100 second. If the ISO rating were 800, a correct exposure would be f16 at 1/800 second. Of course, given the nature of the f-stops and shutter speeds, there are many other equivalent combinations. For example, the exposures of f16 at 1/100 and f8 at 1/400 provide the same amount of light.

Going back to the Sunny 16 rule, if shadows are not so distinct, f11 might be a better aperture than f16. In deep shade or on overcast days where no shadows are created, f5.6 is recommended.

But the G9 does not have f16! The very nature of small sensor, small focal length cameras such as the G9 (not only the G9!) restrict the use of tiny apertures. Instead, we must adapt the G9 bright sun exposure to the Sunny 16 Rule. Actually, that exposure has already been given: f8 at 1/400 is equivalent to f16 at 100. The G9 does have f8.

I shoot my G9 at ISO 80 when possible. The reference exposure in strong sunlight would be f5.6 at 1/640 second based on the Sunny 16 Rule. However, it seems that f5.6 at 1/500 is often appropriate (even if not theoretically equivalent).

This has been a lot of numbers and there are many combinations but an understanding of the relationships between ISO rating, shutter speed and aperture is an essential part of being a photographer.

Hang on to this post or take notice of the blog labels because this will be used as a point of reference in future posts.