Flash length on a HVL-F42AM

[Argonaut]

Does anybody know what the speed of the flash is at 1/32 power? Also, is there anyplace to get an adaptor that puts 1/4x20 thread on the bottom of the flash (attaching to the shoe, I guess)?

Thanks - Argo

[Greg Beetham]

Flash power varies with the distance, f/stop, ISO and angle of coverage also, but manual 1/32 level should be an absolute fixed output and duration; and that's not given in the manual usually now. I saw in the manual on one or two of the older flash units once a while ago that some duration figures were given but I haven't seen that for a long time. I'd say at a guess if one wanted the maximum shortness of duration the highest ISO value would be the first thing to select above even fractional output; that plus a very short working distance, fast lens and angle of view the duration could be exceedingly short, possibly up around 1/50000sec (not with HSS flash of course).
There is the plastic adapter that comes with the flash, it has the 1/4" NC thread in the bottom of it, it's a bit klutzy but it works fine, there is the other much more expensive alternative, the OC shoe that has the OC cable connector in it.
Greg

[Argonaut]

Greg - of course - that plastic foot thingy. I completely forgot. At least it's still in the case.

Regarding high ISO setting etc - I need to operate at low ISO and tiny apertures in order to take high speed flash in the daytime and have ambient light as small a factor as possible. I want to take hummingbird photos to stop (as much as possible) the wing movement and hummingbirds operate in the daytime only. So, I'll try to use the 1/32 manual setting and keep the flash(es) close to the subject.

[Greg Beetham]

Yep the ambient is going to be the main problem there, if it's too strong for the ISO value you stand a good chande of getting one exposure for the ambient overlaid with the exposure from the flash, and the more you stop down to eliminate that problem the slower the flash pulse is going to be (TTL) wise. Another problem is convincing the flash to not use HSS out in daylight, usually the moment you turn the flash on and half press the shutter it takes an ambient reading and wham switches up to HSS.
So yeah the 1/32 option might be one of the better ideas in that endeavour, GN42/32 = GN1.3 that's the only problem, extreme lack of power. At ISO100 it's good for an exposure at 1M with a f1.2 lens, 2 metres at ISO400, but both of those exposures are going to include plenty of daylight. I don't think it's dooable unless you can get very low ambient somehow, ND's won't work either...keep me posted sounds interesting.
Greg

[Argonaut]

twobirdies.jpg

(201.55 KiB) Downloaded 3401 times

Above is a test on a sunny day, in full shade. I used a Christmas ornament birdie to simulate the highly reflective nature of hummingbird plumage. Exposure was 1/160 at f11, ISO 200. Subject to camera backplane distance is 44 inches. Flash to subject distance 24 inches. The image on the left was exposed at 1/8 power; the one on the right at 1/32 power. Both images were adjusted using Lightroom's "Auto" setting (I don't do that often, but this is a test) and both came out remarkably well. And these are JPG originals, not RAW, and I imagine a RAW image will take even more adjusting gracefully. I think I like the adjusted 1/32 better - more gradations on the face, for instance, and I like the darker colors generally. They remind me of my slide-shooting days.

So, as long as I can stay in the shade, I think this might work. Now I just have to find some local hummers and see how they work out in flight. Could take some time.

[Greg Beetham]

Wowzer you lifted it from roughly six stops underexposed (by flash exposure anyway, GN2 @ ISO200 roughly), great work; how much contribution from daylight? What was the exposure reading in the shade there where the subject was?
Greg

ps. Someone was pestering me here and interruping my thought processes, flash was at 2 feet so that could mean only about four stops under by flash? do you have an electric fan you can run on low speed? if it can freeze one of the blades in mid motion it might be good enough to stop the wings of a hummer.

[Greg Beetham]

I did a test with the 5600HSD (F56) M mode WL on 1/32 level at about 2ft from a spinning fan at medium speed (quite fast) and it appeared too stop the fan blades quite ok looking at the rear screen on the A100 at about 6 ft from the fan, M mode 1/125sec f11 @ ISO200, (which on the A100 reverts to ISO100 in M mode, forgot about that). I couldn't get rid of HSS though no matter what I did. The ambient in the interior room was quite dim at 5 seconds f11 @ ISO200, I could try in a brighter place when I get a minute.
Greg

[Greg Beetham]

Having had a chance to reflect on the little test I did it seems TTL is getting involved regardless of the fact that the flash was in M mode and the camera was as well. The main problem is, the exposure was correct? and that could not possibly be right in my book. If the flash was actually regulated to 1/32 level (admittedly I was using a GN56 not a GN42, I don't have an F42) the subject (fan) should still have been quite a few stops underexposed at f11 from about 2 or 2.5 metres away; also the A100 doesn't do ISO200 in M mode (according to the manual), it switches to ISO100 regardless of what is on the rear screen. So the system is outsmarting the operator who was going to contrive an 'incorrect' exposure and 'fixed' things for him...even if he didn't want anything to be 'fixed'.
Greg

[Argonaut]

FourBirdies.jpg

(57.28 KiB) Downloaded 3377 times

I guess different Alphas (I'm using an a700) work differently and sometimes theory can be overcome. The weather is different today so I can't tell you what the natural light exposure was, but in the originals the background is nearly black - it's green foliage like the leaf next to the bird. I checked and the EXIF data shows ISO 200. Above on the left side top is the 1/8 original and below it the 1/8 adjusted. At the right top is 1/32 original and below it 1/32 adjusted. You can see there really are exposure differences in the two originals. What blows my mind is how the 1/32 dark detail can be revealed - LR put in +.95 exposure, + 19 fill light, +20 brightness and -25 contrast. There is some noise, but it's far from obvious. The 1/8 was adjusted to +32 fill light and -25 contrast only.

[Greg Beetham]

I can confirm anyway that the pulse seems fast enough to freeze a high speed object despite the system doing it's best to thwart the intended result and supply a correct exposure in preference to doing what I asked it to do. I couldn't get rid of HSS on the screen of the 56 that was my main worry as HSS is supposedly flat flash that is long enough to cover the 'slow' shutter cycle (the cycle is still slow even if the speed is fast so to speak) and useless for the purpose of freezing high speed motion.
Whatever it was going on inside the camera and flash on that occasion is unknown to me, whatever it was it wasn't M mode that's for sure, and HSS wasn't behaving like HSS should either, not at 1/125sec. very weird...but it still stopped high speed motion so that's the main thing.
In those images of yours I think I like the 1/8 unchanged version better than the modified one; although the program looks like it did a good job on the 1/32 image.
Greg