Studio flash and high speed sync

I've been racking my brains over this but can't come up with an answer,

How can you get studio flash units to sync at a speed greater than 1/180sec,

Will the AF360/540FGZ emit a pre-flash when used in HSS sync mode?

Answer: You can't

The reason is this: At speeds higher than the flash sync speed the shutter isn't completely open at any time -

* You press the shutter
* The leading shutter curtain starts moving
* Before the leading curtain reaches the end, the trailing curtain follows
* So the CCD (or film) is exposed as a moving strip.

(Hope I explained that clearly enough )

Consequently, when the AF540 and AF360 do HSS mode they fire continuous bursts of light to "machine-gun" the light as the hole in the shutter makes its way down the CCD.

Even if you could get other equipment to sync you'd only get a small strip of the image exposed correctly


If you want higher shutter speeds in a studio environment then you'll have to use continuous lighting rather than flash blocs

Matt

Thanks for the reply Matt, I had come to that conclusion, suppose I just wanted it comfirmed.

As a non pentax follow up to my original post regarding HSS in the studio.

I was playing around with my Fuji S7000 and one of my AF360FGZ's. I was initially very surprised to find that with the external flash setting enabled on the Fuji I was able to sync the AF360FGZ all the way up to the Fuji's top shutter speed of 1/10000. When I thought about it I relazised that this is possible because, if I'm thinking correctly, the Fuji does not have a mechanical shutter. It also worked fine with an old Sunpak 888.

Nice to know that I have an option to go higher than 1/180 using strobes instead of always on tungsten lights.

Will be giving it a try in the studio this Sunday.

Brian, why do you want to sync higher than 180 in a studio? Depending on the flash head in use your effective exposure could well be 1/20000 of a second at f*. Outdoors, of course, is another matter and that's why Pentax have made leaf shutter lenses for the 645 and 67, probably aimed at wedding photographers primarily.

Ken

Correct

Not sure about the electronics of it, but I think the "shutter speed" is simulated by dumping the charge in the CCD and reading out after the time delay.

All digicams are like this - CCD always active (that's how they get the live preview).

Matt

To freeze movement, or have I got my thinking all wrong?

Yes. Your effective shutter speed (or duration of exposure) is the duration of the flash, which is usually at most 1/1000 second, and often much less.

You will almost never have a problem freezing movement in a studio. The only time it might happen is if you have a lot of ambient light. Solution - switch off the overhead lights, or draw the curtains.

G

PS: There is an alternative to tungsten. Very powerful fluorescent bulbs are now available, colour-balanced to daylight. Unlike tungsten, they run cool(ish), and don't draw much power. They have an American ES fitting. I'm planning to try a couple.

I'm having a brain dead day/week
In dire need of some sunshine :arrow: :arrow: :arrow: ................Taxi please..............to the airport
G, Do let us know how the fluorescent bulbs perform, sounds a good alternative to tungsten.

I wonder, does the fuji not have a mechanical shutter, or does it have aleaf type shutter in the lens?

Don,
AFAIK, the compact digicams have aperture blades in the iris and a shutter that is used to seal off the CCD (to protect it. At least my old Canon S30 did).

Don't forget they are more like video cameras - the CCD is always "exposed" so you can get the live preview.
http://en.wikipedia.org/wiki/Live-Preview_Digital_camera

(Interestingly the Canon 20Da and the 1D MkIII have Live Preview where they lock the mirror up and stream the CCD data to the LCD. Now that on a K10D would be nice!!)

Matt

There is an even better range of lighting which I use quite a lot called Kino-Flo Diva Lites (www.kinoflo.com). Whilst on the subject of lighting, I recently bought a really good book called 'The Complete Guide to Light and Lighting in Digital Photography' by Michael Freeman and published by Ilex and £19.99 from Waterstones. It covers every aspect and almost every piece of kit I've ever come across; I cant recommend it highly enough.

Ken

PS
When quoting on this forum is there a way to include 'Gartmore wrote:' or do you just type it in?

If you click on the 'Quote' button, top right of the post you want to quote from, then it will have the 'Gartmore wrote' text in it. Otherwise, just add ="Gartmore" after the quote tag, within the brackets, and that would do it.

Dan

doh!!! I'm obviously having a Homer moment, thanks Daniel