If you have a question for one of our experts stationed at a desk at our monthly meetings, or for one of our general meetings devoted to Q&A, that may require some preliminary research, then please post it here.
If you have a question for one of our experts stationed at a desk at our monthly meetings, or for one of our general meetings devoted to Q&A, that may require some preliminary research, then please post it here.
I am not sure if this will be applicable for the experts this month but I am curious.
So in the past we have seen special lighting instruments, specifically I am thinking of Gerry's flashes that attach to the lens. This showed stunning results when used with macro work. This allowed for a better depth of field while still allowing for motion to be stopped My question is sort of a two parter. First what is the difference between a two flash system as I am referencing and a ring flash? Are they interchangeable or are they each intended for very different uses?
My second question, is there a wattage equivalent of a low power (or power commonly used) on a flash , for instance can flashes used on a low power be exchanged for a continuous ring light. I have recently seen a project that uses led rings intended for car lights used as ring lights around the lens.
Having spent a decent amount of time learning about flash several years back, I think that topic - at least in the detail you ask about - deserves more attention than can be given in a walk-up environment. It involves light color, flash power, freezing (or not) with flash, and more. It might be time to have a good seminar on flash; the club really hasn't touched that one for a while. The limitation of the walk-up format is that only a few people benefit, so it's more appropriate for things that you might ask at your camera shop: how do I set the camera to do this, or what lens would be a good choice for that?
There wasn't any real action at the Canon table last month; I guess Canon owners don't have problems. :)
I was at the Canon table asking Deb Snelson about polarizing filters. She was very helpful.
Re your flash question, Rob: A ring flash works very much like the two flashes you saw mounted on the front of my macro lens. The main difference is that a ring flash outputs such uniform light that it tends to make your images look flat, without the texture that comes from creating shadows. With a flash on either side of the lens, you can set one unit to a slightly lower power than the other, and that will create a slight shadow and thereby add a sense of depth and texture.
Regarding your second question, I have no experience with the system you're describing and therefore can't help you with it. John Hulburt or Gene Runion may know more.
I was looking at the questions more in terms of how they could be addressed at a meeting, but I can take a stab at the second one.
Your flash has a guide number. A 50m GN means that a full pop will correctly illuminate a subject at (50 meters / f) at 100 ISO. There is no shutter speed in there because the flash is essentially instantaneous. Continuous light, OTOH, has a time factor and a great example is Sunny 16: "daylight power" will correctly illuminate a subject at any distance at f/16, 1/100 and ISO 100. Digging deeper, it applies for any shutter speed = ISO and of course you can trade time for ISO for aperture all day long.
So, the big difference keeping you from making a direct comparison is that you have time as a factor in continuous light. Just comparing one proper exposure to the other with easy numbers, if the 50m flash exposes properly at (50/16) meters, or roughly ten feet, then you would have to simulate daylight on that subject to get the same correct exposure at 1/100 second. That's a lot of light. In real life you'll end up with a much longer exposure because you can't get that kind of light power onto the subject at ten feet. Compare the roughly 10,000 lumens/sf of sun power to your lumens/sf (at your desired distance) of your LEDs.
Looks like for a 10' distance to subject, the 50m flash is equivalent to 10,000 lumens/sf for 1/100 second, or 100 lumens/sf for 1 second. At that point you need to figure out how focused your LEDs are to tell how many lumens they are putting onto a square foot from that distance. You need to use the inverse square law to derate your LED over the distance. Your answer will not be in Watts since they are not a measure of light output.
Yes i may have misspoke with Watts, i understand lumens are a better way to look at it. But that doesn't necessarily stop people from using watts sometimes as a value.
It seems like yes that a flash is far more useful than a cheap ring light. Also it would seem for doing any close up work, which I would intend to do, a correctly adjusted and diffused flash still is better than a ring light. It was just a thought at increasing light for doing macro work of lets say butterflies or bees or some other fast moving insect.
I will say that as Gerry said, that a ring light might be used for modeled photos where shadows arent as desired, which is how I have seen it in many cases.
Yes, flash is more useful but many people use LEDs because they are cheaper and easier to use. The disadvantages that I see are the much lower output (needing longer exposures) and the probably compromised color balance (this will probably vary a lot with the actual LEDs you are using).
As for ring flash (or similar diffused light) vs directional light, a few years ago Gerry organized a macro workshop out at Ivy Creek. We had a few examples there of how much of a texture improvement you can get by controlling the light direction. Let me try to find them.