understanding flash duration? - FM Forums

Register · Search · Software · Join Upload & Sell · Hosting

Moderated by: Fred Miranda

FM Forums \| Lighting & Studio Techniques \| Join Upload & Sell	Search Used
1 2 end

Archive 2010 · understanding flash duration?

Two23
Offline
Upload & Sell: Off

p.2 #1 · understanding flash duration?

"Railroad security?" The only thing I ever see out here in the Dakotas are cows. Train crews know me and sometimes invite me up into the cabs to warm up while they're waiting in a siding. Never had a problem.

Kent in SD

Feb 04, 2010 at 02:11 PM

Bryan Beasleigh
Offline
Upload & Sell: Off

p.2 #2 · understanding flash duration?

The CN police can be a royal pain in the asp up here. They think they have more power than they really do.

Feb 04, 2010 at 02:27 PM

Ryan Pream
Offline
Upload & Sell: Off

p.2 #3 · understanding flash duration?

So how would say the Einstein compare to the Profoto D1 500ws model? Profoto specifies that as 1/1000 - 1/2600 at t0.5. I realize the Einstein gets faster the lower the power, but I'm not clear on how that works with the D1.

Ryan

Feb 04, 2010 at 04:30 PM

E-Vener
Offline
Dedicated FM
Upload & Sell: Off

p.2 #4 · understanding flash duration?

paul buff has been saying that at all power levels below ful lthe flash duratio ntimes are measured at the t0.1 standard . the D1 doesn't use the same IGBT type electronics that the Einstein uses so to find the the t0.1 times multiply the t0.5 reading by 3x . In other words a t0.5 of 1/1000 means the t0.1 duration is 1/333rd second.

The D1 is a terrific flash. I like it a lot. However if you are photographing things or people in swift motion you might see a little blur.

Feb 04, 2010 at 04:57 PM

Paul Buff
Offline
Account Locked

p.2 #5 · understanding flash duration?

Ellis - correct. But the t.1 = 3 times t.5 only applies to non-IGBT flashes. At minimum power the D1 looks like t.1 = 1/333 while Einstein would be in the 1/10,000 range.

Kent, I agree about your shots . . . really fast durations would freeze the train motion cold, but would also eliminate the snow blur, leaving the flakes looking like dust spots . . . like shooting fireworks with a short exposure time.

Feb 05, 2010 at 08:37 PM

Ryan Pream
Offline
Upload & Sell: Off

p.2 #6 · understanding flash duration?

So the D1 get's longer flash durations as the power lowers where are the Einstein get's shorter. I know the D1 is supposed to have very good color accuracy, so I guess this is some additional circuitry compared with a standard flash?

I'd be curious in learning more on IGBT etc. Any good resources? Something that is understandable by a non electrical engineer would be great!

Ryan

Feb 05, 2010 at 10:10 PM

RMS956
Offline
Upload & Sell: Off

p.2 #7 · understanding flash duration?

Ryan Pream wrote:
So the D1 get's longer flash durations as the power lowers where are the Einstein get's shorter. I know the D1 is supposed to have very good color accuracy, so I guess this is some additional circuitry compared with a standard flash?

Ryan

Yes I believe the Einstein has two modes of operation:
1. Normal flash with highly accurate and consistant color.
2. Action flash using the IGBT circuit with no accurate color.
Don't think you can have both in a studio type flash.

RMS

Feb 05, 2010 at 10:40 PM

Paul Buff
Offline
Account Locked

p.2 #8 · understanding flash duration?

RMS956 wrote:
Ryan Pream wrote:
So the D1 get's longer flash durations as the power lowers where are the Einstein get's shorter. I know the D1 is supposed to have very good color accuracy, so I guess this is some additional circuitry compared with a standard flash?

Ryan

Yes I believe the Einstein has two modes of operation:
1. Normal flash with highly accurate and consistant color.
2. Action flash using the IGBT circuit with no accurate color.
Don't think you can have both in a studio type flash.

RMS

Both Einstein modes use the IGBT circuitry, and both shorten the flash duration dramatically as you lower power. The difference is, in Color Mode the shortening of durations is not quite as dramatic and occurs a bit more gradually, but the color remains constant, within +/- 50°K. In Action Mode the duration shortening is more rapid and dramatic but the color temperature rises as you reduce power.

Most users will use Color Mode most or all the time, reserving Action Mode for shots that demand the very fastest action stopping at the cost of some color shift. In color Mode, the t.1 duration is about 1/1700 at 1/2 power and falls to about 1/6000 t.1 at 1/128 power. In action Mode t.1 is about 1/2000 at 1/2 power and falls to below 1/10,000 at 1:128 Power.

Since the D1 is not IGBT controlled I would expect it's color to warm by about 80° per halving of power as essentially all units that use other voltage controlled power control.

Feb 06, 2010 at 01:06 AM

E-Vener
Offline
Dedicated FM
Upload & Sell: Off

p.2 #9 · understanding flash duration?

D1 flash duration gets shorter as you dial down power, but nearly as dramatically astot looks like the Buff Einstein fd will. I think you are confusing t0.1 with t0.5 numbers.

Feb 06, 2010 at 01:59 AM

Paul Buff
Offline
Account Locked

p.2 #10 · understanding flash duration?

Ellis, are you sure about this? The specs look exactly like a non IGBT flash with Full to 1/64 power control via variable capacitor voltage. This power range on this basis would yield exactly the 1/2600 & Full and 1/1000 @ 1/64 t.5 times stated. It would also cause a color shift of about 450° between Full and 1/64 power.

http://www.bhphotovideo.com/c/product/605740-REG/Profoto_901023_D1_500_w_s_Monolight.html#specifications

Feb 06, 2010 at 04:46 AM

E-Vener
Offline
Dedicated FM
Upload & Sell: Off

p.2 #11 · understanding flash duration?

Comment Deleted.

Edited on Feb 06, 2010 at 04:47 PM · View previous versions

Feb 06, 2010 at 04:42 PM

E-Vener
Offline
Dedicated FM
Upload & Sell: Off

p.2 #12 · understanding flash duration?

I meant "not nearly as dramatically as the Einstein".

Feb 06, 2010 at 04:46 PM

Bryan Beasleigh
Offline
Upload & Sell: Off

p.2 #13 · understanding flash duration?

I can see the benefits of the switchable capacitor banks to manipulate flash duration as well as capacity. I was experimenting with my 580EX in manual mode and at full power could see the difference of the exposure between 1/180 and 1/250 of a second shutter speed. The full power T=0.1 is clearly below 1/250

I haven't bought my monolites yet but the White lightening and/or Einstein are starting to look like a better way to go.

Feb 06, 2010 at 09:50 PM

RDKirk
Offline
Dedicated FM
Upload & Sell: Off

p.2 #14 · understanding flash duration?

Note that while the snow was streaking in the 1/600 sec. of flash duration, the train was not, despite moving at the same speed.

I would theorize that was a combination of reflectivity and a double effect caused by distance. The snow clumps are not only white, they're crystaline--as reflective as a safety reflector. You're seeing, I think, the effect of the full t.1 duration of the flash because they substantially reflect even the trailing tail of the flash duratin.

The closest ones--receiving the greatest exposure--are streaking most. That would be the effect of their proximity showing more distance displacement across the sensor. The same thing affects the train--it takes a higher shutter speed to "stop" a close moving object than a distant moving object.

Feb 08, 2010 at 01:21 PM

Paul Buff
Offline
Account Locked

p.2 #15 · understanding flash duration?

Absolutely correct RD. The snow flakes are closer and smaller, and they are overexposed if they are in the light path. All of this adds to the blur relative to the train. If, for instance, they are 3f overexposed, they are down to full exposure at t.1 time. As for distance, the flakes cross the frame much faster than does the train.

Feb 08, 2010 at 04:36 PM

1 2 end
FM Forums \| Lighting & Studio Techniques \| Join Upload & Sell 1 2 end