built in flash effect on slave unit and photo quality

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Re: built in flash effect on slave unit and photo quality

Postby Mudduck » Dec 8, 2009 3:15 pm

Ok bought a cheap slave flash(sunpakd18t) to get my toes wet. Worked good close but not at distance. Found the sensor was on the flash side of the unit. I disassembled it and moved the sensor to the top of the unit. Worked great when testing in a 40 x 60 dark building for about 10 photos then all the sudden my photos whould turn up black when the slave flash activates. I changed no settings. Camera still works fine without slave flash. Any suggestions??
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Re: built in flash effect on slave unit and photo quality

Postby NZcaver » Dec 8, 2009 5:08 pm

Mudduck wrote:Ok bought a cheap slave flash(sunpakd18t) to get my toes wet. Worked good close but not at distance. Found the sensor was on the flash side of the unit. I disassembled it and moved the sensor to the top of the unit. Worked great when testing in a 40 x 60 dark building for about 10 photos then all the sudden my photos whould turn up black when the slave flash activates. I changed no settings. Camera still works fine without slave flash. Any suggestions??

Does your camera fire a single flash with each shot, or is there a quick pre-flash or two before the 'main' flash?
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Re: built in flash effect on slave unit and photo quality

Postby Mudduck » Dec 8, 2009 9:36 pm

NZcaver wrote:Does your camera fire a single flash with each shot, or is there a quick pre-flash or two before the 'main' flash?


It fires a quick two best we can tell. the camera is a Kodak EasyShare C613. I realize this is sub-standard equipment but as I said cave photography is something really new to me(with respect to "nice" photos) and I like to dip a toe to see what direction to go in before taking a big step. The thing that boogles my mind is why it worked great at first. I checked multiple times to be sure the "automatic" settings were'nt changed between practice shots.
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Re: built in flash effect on slave unit and photo quality

Postby captnemo » Dec 8, 2009 10:07 pm

is this the flash your using? http://www.amazon.com/gp/product/B00009W3T7/ref=cm_rdp_product/178-0255418-5267157
If so the reviews are not favourable- a common complaint seems to be inconsistent results and that it just stops working. Sound familiar?
Here's a review on B&H's website by someone who bought one-
Used it as a slave for flash fill in those "emergencies." It worked great for about 40 pictures, but now the light sensor reacts so slow to my main flash, my camera never catches its light. I've tried changing batteries, cleaning the battery contacts, and even the light sensor itself and it still doesn't work right. It does, however, still work properly when seated on a hot shoe.


I think I'd send it back and shop for something with a better reputation, like a vivtar 285(you'd need an optical slave as well), or one of these http://www.mpex.com/browse.cfm/4,12311.html that have a built in optical slave, I don't know how well either would deal with the pre-flash on your kodak, another option is the digiflash http://www.mpex.com/browse.cfm/4,12311.html I have one of these, I've been hauling it around for a few years and it still works well, has a setting for pre-flash which I've tested with a couple point and shoots and works. The sensor is on the front though, so not the most sensitive unit. These all cost more then the sunpak 018st, but the savings in frustration will probably be well worth it.
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Re: built in flash effect on slave unit and photo quality

Postby OpenTrackRacer » Dec 10, 2009 2:02 pm

Are you looking to trigger an off-camera flash to avoid reflections from dust and water vapor in the air or to achieve side lighting? After some extensive testing I've found that even the built-in popup flash on a DSLR will go a very long way towards eliminating reflections from particles in the air. I can only think of a few times where I've had any reflections worth noting that they happened in very dusty environments. A hot shoe mounted flash is even better but obviously bulkier.

Before I started bringing a DSLR I was using a point and shoot with full manual controls. I'd hand hold it (or set it on something for side lighting) and simply open the shutter for 2 seconds or so. In that time I would manually trigger an old flash I was holding with my other hand. It's not the cleanest or quickest method but it did produce good results.

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Re: built in flash effect on slave unit and photo quality

Postby NZcaver » Dec 10, 2009 4:34 pm

OpenTrackRacer wrote:Before I started bringing a DSLR I was using a point and shoot with full manual controls. I'd hand hold it (or set it on something for side lighting) and simply open the shutter for 2 seconds or so. In that time I would manually trigger an old flash I was holding with my other hand. It's not the cleanest or quickest method but it did produce good results.

I used to do the same thing, but your subjects either need to be perfectly still or they have to turn their lights off (or both). Otherwise you get streaky light photos.

Hmmm, DSLRs. I have one, but it doesn't go caving. Too heavy, too bulky, too expensive. There are numerous 'mid-size' digital camera models with full manual settings and hot shoe mounts which can produce superb quality images. They're smaller and cheaper than DSLRs, too. Even some compact cameras without a hot shoe have manual settings which also disable the digital pre-flash. Particularly Canons. A single flash makes triggering a remote (optical) slave much simpler.

Mudduck wrote:
NZcaver wrote:Does your camera fire a single flash with each shot, or is there a quick pre-flash or two before the 'main' flash?

It fires a quick two best we can tell. the camera is a Kodak EasyShare C613. I realize this is sub-standard equipment but as I said cave photography is something really new to me(with respect to "nice" photos) and I like to dip a toe to see what direction to go in before taking a big step. The thing that boogles my mind is why it worked great at first. I checked multiple times to be sure the "automatic" settings were'nt changed between practice shots.

This is just a shot in the dark (bad pun) :big grin: but it *might* be this. Assuming your camera fires two quick flashes for each shot, the first flash helps set exposure/white balance, and the second flash illuminates the scene as the camera captures the image. With fresh batteries, your flashgun probably mimicked those two flashes by recycling almost instantly between flashes. But as the battery capacity declined slightly, your flashgun took longer to recycle after each flash. This can result in the flashgun triggering with the pre-flash, but not with the main flash immediately after it. Resulting in... dark photos.
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Re: built in flash effect on slave unit and photo quality

Postby pub » Dec 10, 2009 5:54 pm

NZcaver wrote:This can result in the flashgun triggering with the pre-flash, but not with the main flash immediately after it. Resulting in... dark photos.

If this is the case, try using the "Fill" setting for the on-camera flash, see photo below:

Image

In the "Red-eye" setting, "The flash fires twice—once, then again when the picture is taken."
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Re: built in flash effect on slave unit and photo quality

Postby NZcaver » Dec 11, 2009 3:28 pm

pub wrote:
NZcaver wrote:This can result in the flashgun triggering with the pre-flash, but not with the main flash immediately after it. Resulting in... dark photos.

If this is the case, try using the "Fill" setting for the on-camera flash, see photo below:

Image

In the "Red-eye" setting, "The flash fires twice—once, then again when the picture is taken."

This is good information, but please note the red-eye setting is NOT the same pre-flash(es) I was talking about. Many point-and-shoot digital cameras fire one or more pre-flashes to set the exposure/white balance in automatic modes regardless of whether (anti-) red-eye mode is selected or not. If "Red-eye" is selected, most cameras fire an additional barrage of quick pre-flashes but these are very counter-productive for cave photography when using an external slave flash.

However, Mudduck could try "Fill" mode on his camera to see if it helps. Maybe it does disable the pre-flash? It's worth a shot.
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Re: built in flash effect on slave unit and photo quality

Postby OpenTrackRacer » Dec 11, 2009 4:11 pm

Well, I sure has heck won't be bringing my 40D underground but you might be surprised with what you can find. I picked up a well used Canon Digital Rebel (300D) with an 18-55mm kit lens for $150. It's pretty small (it fits in the front pocket of my gear vest) and I'm not too concerned with killing it. It's done will with the dust so far but would obviously need some protection in a wet environment. The pictures I've gotten out of it blow away anything I'd done before with either camera I'd used underground before.

NZcaver wrote:Hmmm, DSLRs. I have one, but it doesn't go caving. Too heavy, too bulky, too expensive. There are numerous 'mid-size' digital camera models with full manual settings and hot shoe mounts which can produce superb quality images. They're smaller and cheaper than DSLRs, too. Even some compact cameras without a hot shoe have manual settings which also disable the digital pre-flash. Particularly Canons. A single flash makes triggering a remote (optical) slave much simpler.
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Re: built in flash effect on slave unit and photo quality

Postby NZcaver » Dec 12, 2009 4:53 pm

OpenTrackRacer wrote:Well, I sure has heck won't be bringing my 40D underground but you might be surprised with what you can find. I picked up a well used Canon Digital Rebel (300D) with an 18-55mm kit lens for $150.

Good deal. My new DSLR is also a 40D, but my normal 'caving camera' is an Olympus C-5050 zoom. It's old and has a huge shutter delay, but you can't beat the f1.8 lens and SHARP images.
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