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Flash with Macro photography

 
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Carl_Constantine



Joined: 21 May 2006
Posts: 55
Location: Victoria, BC, Canada

PostPosted: Mon May 22, 2006 7:06 pm    Post subject: Flash with Macro photography Reply with quote

I've read in a couple spots on this forum that you need to get the flash closer to the subject when taking pics. I have a couple questions on this.

1) How do you not blow out/over-expose the subject with the flash that close, particlarly something white.

2) do you always use flash for macr work?

3) Ok, so one more. How do you reduce the glare on your lense when the flash is that close?

I bought with my Canon 300D a Sigma DG-Super 500 speedlight and I have an omnibounce diffuser to soften the flash a bit and act as more fill flash (or at least that's my thought). How would I best use this setup in Macro work? (don't have a flash bracket as of yet, or remote flash transeiver either)
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twebster
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Joined: 19 Apr 2004
Posts: 1518
Location: Phoenix "Valley of the Sun", Arizona, USA

PostPosted: Mon May 22, 2006 10:06 pm    Post subject: Reply with quote

Hi ya' Carl, Very Happy

Whites will get blown out regardless of the position of the flash. I control the glare from the flash by using polarizing filters on the flash and the lens. Getting the flash close to your subject helps control shadows. The closer the flash is to the subject, the less the flash acts as a point light source and the softer the resulting shadows. I like to position my flash right over the end of my lens. The use of a lens hood will prevent the flash from directly striking the front element of the lens. Here's a couple of articles I wrote about electronic flash for macro photography...

Polarized Electronic Flash

Kirk Enterprises Macro Flash Bracket

Best regards, Very Happy
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Carl_Constantine



Joined: 21 May 2006
Posts: 55
Location: Victoria, BC, Canada

PostPosted: Tue May 23, 2006 3:06 pm    Post subject: Reply with quote

ok, interesting article. So do you always use polarized flash? Or do you have two different flashes for different types of work. For example, general photography and macro work? I just think it would be a hassle to continuously remove and add the filter to the flash all the time.
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twebster
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Location: Phoenix "Valley of the Sun", Arizona, USA

PostPosted: Tue May 23, 2006 9:45 pm    Post subject: Reply with quote

Hi ya' Carl, Very Happy

Quote:
So do you always use polarized flash?


Not always. Lately I've been using the flash without polarizing filter or diffuser.

Quote:
Or do you have two different flashes for different types of work. For example, general photography and macro work? I just think it would be a hassle to continuously remove and add the filter to the flash all the time.


It really isn't a problem to put the filter on and take it off the flash. I don't shoot much of anything but macro, anyhow. I just leave the filter on the flash 90% of the time and either put on or take off the polarizing filter from the lens. Leaving the polarizing filter on the flash just cuts the output of the flash a little bit. At macro distances, this is negligible.

Best regards, Very Happy
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rjlittlefield



Joined: 06 May 2005
Posts: 727
Location: Richland, WA, USA

PostPosted: Tue May 23, 2006 9:56 pm    Post subject: Reply with quote

Carl,

Let me take a different tack at answering your questions.

Quote:

1) How do you not blow out/over-expose the subject with the flash that close, particlarly something white.

2) do you always use flash for macr work?

3) Ok, so one more. How do you reduce the glare on your lense when the flash is that close?

I bought with my Canon 300D a Sigma DG-Super 500 speedlight and I have an omnibounce diffuser to soften the flash a bit and act as more fill flash (or at least that's my thought). How would I best use this setup in Macro work? (don't have a flash bracket as of yet, or remote flash transeiver either)

1a. You avoid over-exposure by reducing the light output of the flash and/or stopping down the camera lens. In auto-exposure mode, your camera and flash will do this automatically. Your flash can probably operate reliably at levels that are plenty low enough to handle anything you want to do. If it can't, you can always cut its output even farther by taping a layer or two of ordinary paper over the face.

1b. If your subject is small and close, compared to the background, then you'll have a lot of dark background that can mislead the camera's metering and blow out the small subject. To get around that, you can set "exposure compensation" to decrease the exposure, while still allowing automatic operation. Some experience will tell you what the right setting is.

1c. Assuming proper exposure, it's not really the whites that will blow out, it's the "shinys". Basic exposure control as described above handles matte surfaces of all colors just fine -- if your grays are properly exposed, then your whites will be too. But shiny surfaces will reflect an image of the flash itself. That reflection is almost always so bright that it blows out. There are at least three attacks on that problem: use Tom's crossed polarizers trick, put the strobe behind a huge diffuser (see Wim Van Egmond's sketch here), or bounce it into a big reflector.

2. Lots of good macro work has been done using just available light, particularly direct sun. However, flash often makes the pictures easier or better. One way is by providing enough more light to allow shorter exposure time and/or smaller F-stop. A second is to provide fill to lighten up dark shadows or the fronts of backlit subjects.

3. To avoid lens flare, use a hood and/or keep the flash behind the lens. In macro work, your field of view is so small that you can make some pretty extreme lens hoods if you like. In the old days, when my lenses suffered worse from flare, I would sometimes make a roll of black paper that extended almost to the subject. My current lenses don't have flare problems and I mostly don't worry about it.

How to use what you have? For filling in shadows and backlit subjects, just put the flash on the camera and shoot away -- chances are it'll work fine. To use flash for main lighting, make one of Wim's diffusers -- it's a few minutes work with paper, tape, and aluminum foil. Just be sure to make it big enough that stuff in your field of view can't see the flash directly.

By the way, the omnibounce won't usually work as well for macro as it does in your living room. The problem is that it relies on light being indirectly reflected onto the subject from the environment, especially the ceiling and walls. For most macro shots, there's not enough environment close enough above or beside to do that.

One last thing... If you keep reading about how to use flash, at some point you'll run up against "flash exposure compensation" (FEC). That's a way of telling the camera what ratio you want, between ambient and flash. I think your 300D does not have FEC as it comes from the factory, but numerous sources say that it can be added using some "hacked firmware". Google on 300D flash exposure compensation and you'll get a lot of discussion and links. (Yes, I do have the hacked firmware installed on my 300D. It works fine, but I only use it for mirror lockup. I have no need for FEC and haven't tried that function.)

--Rik
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Carl_Constantine



Joined: 21 May 2006
Posts: 55
Location: Victoria, BC, Canada

PostPosted: Wed May 24, 2006 4:00 pm    Post subject: Reply with quote

Wow, thanks for the help Rik and Tom. I'll do some more testing and practice with my flash and see what I can come up with.
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