600EX-RT

[Rongates]

Can I set the flash to subject distance on my 600EX-RT to get f/stop?

[Skirball]

As in, use it like a light meter and get it to tell you what f/stop to use for a given power output in manual?  I don't think so.  You're either in eTTL full auto, which compensates for aperture or ISO, or it's full manual where you simply dial up/down the power.

There are the external modes, both an auto and a manual.  It's a "thyrister" mode of old, where the flash determines how much light to put into a scene by measuring the reflected light and calculating in the ISO and aperture settings.  It's mildly useful for light painting, but I can't think of much of a use beyond that.

[Rongates]

Thanks.  I've recently read Bryan Peterson's flash book and he is a Nikon person but he talks frequently about setting the distance scale on the back of the flash to ascertain the correct f/stop-power in manual without constantly having to guess what is the correct f/stop-power setting for a given distance.  So, if you want to shoot at a wide open f/stop to gain more background exposure then the scale would tell you.  Otherwise, it's a guess.

[Skirball]

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@Rongates wrote:

Thanks.  I've recently read Bryan Peterson's flash book and he is a Nikon person but he talks frequently about setting the distance scale on the back of the flash to ascertain the correct f/stop-power in manual without constantly having to guess what is the correct f/stop-power setting for a given distance.  So, if you want to shoot at a wide open f/stop to gain more background exposure then the scale would tell you.  Otherwise, it's a guess.

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Well there's the distance scale.  But you wouldn't set the aperture on the flash, because it already knows what it is if the flash is on camera.  Sounds like an old flash to me.   I know the 580exII has a distance scale, I'd imagine the 600ex-RT has one as well.  I can't say I've ever used it though.  All it does is tell you how far away your subjectshould be given the camera settings and the flash power choosen.  Assuming that your flash is on camera, in manual, and you're shooting it straight forward, bare.  Honestly, I'd recommend you don't do that.

If my flash is on-camera, which is exceedingly rare, I'm most likely in eTTL or on a very low powered manual fill. Even then, I'm usually bouncing either off a wall or a DIY bounce (read: any piece of white paper I can find).  The only time I'd shoot it straight forward bare is if I was trying to fill in for some really bright sun.

Most the time my flash is off-camera, and uses a modifier, so the scale is worthless.  The whole point of the 600ex-RT is to get it off camera.

[Rongates]

I agree.  I wouldn't use it on camera.  Let's say my background is f/5.6 and I want to photograph someone or something in the foreground that I'd like to be f/4 then it would be helpful to know how far away the flash should be to get that f/stop.  THe camera might be to the side of farther away.  By setting the flash to subject distance on the flash I could determine that in order to have the flash expose for f/4 I need to either move the flash forward or back.  The camera could be anywhere.  From what I gather the 600EX-RT may not be able to do what I want it to do.  An older flash might have had that capability. 

[Skirball · Accepted solution]

Yes, but if you're using modifiers that all goes out the window.  If you're going to be measuring your background, presumably with a light meter, then why not just use a light meter for the flash too?  

Older flashes had these features because they were designed for film.  You didn't know what you were going to get until you developed your film.  There's a reason why the no longer include them, they just don't offer much benefit for digital.   I'd even argue that with some practice you can come just as close with a first guess as you could with a scale.  I can usually come pretty close the first time with my flashes, in any of my softboxes or umbrellas, at both ISO 100 and 400; just because I do it a lot.  Regardless, it's digital.  Take a shot, check it out with the histogram, and readjust.  If you insist, use a lightmeter.

[Rongates]

Thanks for all your input.  I wouldn't use a lightmeter but would meter with my camera to get the background.  And yes I can take test shots and redo as necessary.  I was simply trying to avoid having to take multiple shots to get where I needed to be.  I have been shooting primarily available light and need to improve my flash photography.  Most of what I would be shooting would be set-up shots so it's not impossible to take test shots.  Thanks again for your suggestions!