Can anyone convert t0.5 to t0.1 please?

treeman

treeman

Suspended / Banned
Messages
4,094
Name
Mark
Edit My Images
No
Or is it not that simple?

Just want to find out how 1/2200 sec flash duration equates to shutter speed.

I 'd like to sync at 800th sec on the camera (leaf shutter) and not sure if that'll be too fast for 1/2200th flash duration (t0.5).

Thank in advance
 
I'm not an expert...

But doesn't this vary by make? As the shape of the flash output isn't always the same.

But as above: I might have made that up.
 
Depends on the flash/type of flash... w/ an IGBT strobe/speedlight T0.1 can be about the same as the T0.5 (at some power settings). But most leaf shutters will sync up to 1/800-1/1600 SS without regards to the flash duration.

A good estimate for T0.1 with non-IGBT heads is ~ 1/3 of T0.5. 1/800 ss should be a pretty good match... even if it's slightly off you won't really see an issue (might have to adjust the power a bit).
 
Last edited:
Ok thanks, I hadn't thought about different flash types! Its a Profoto B3 Air S which I think isn't IGBT.
I did have 1/3 figure in my head so guess I heard that somewhere before too.

I've got the option of trying it out but just wanted to check whether it was even going to be vaguely likely to work, before I waste my time. Thanks Phil & Steven.
 
treeman said:
Ok thanks, I hadn't thought about different flash types! Its a Profoto B3 Air S which I think isn't IGBT.
I did have 1/3 figure in my head so guess I heard that somewhere before too.

I've got the option of trying it out but just wanted to check whether it was even going to be vaguely likely to work, before I waste my time. Thanks Phil & Steven.
Click to expand...
I've just been reading @HoppyUK 's review of portable lights in Professional Photo and it seems that the 1/3 figure is 'close enough for jazz'
 
This isn't all that simple.
In very general terms, the 1/3 ration isn't usually all that far off the mark, e.g. t0.5 of 1500 typically approximates t 0.1 of 500, where conventional technology flash heads are concerned. But it does vary between manufacturers, and although I understand the physics very well, I don't understand the maths side of it and so I can't explain why, for example, some Elinchrom heads have a ratio that's closer to 1/2 and some of the very cheap heads are in the region of 1/4.

And, once we leave conventional flash technology and move to IGBT, t.05 and t.01 figures become very close to each other as the power setting is reduced further and further.

As for your specific question, you should be OK - but bear in mind that leaf shutters aren't a distinct on/off, they open from the centre and close from the edge, so the centre is open for longer than the edge - not the same as the two moving blinds of a FP shutter, but not all done by magic either.
 
mike weeks said:
Actually as far as I understand it is much less relevant as you do not get the black edge problem, what you may do is lose a bit of flash power

Mike
Click to expand...
More like a vignette effect... but you have to be pushing it pretty hard for it to become strong.
 
Last edited:
treeman said:
Or is it not that simple?

Just want to find out how 1/2200 sec flash duration equates to shutter speed.

I 'd like to sync at 800th sec on the camera (leaf shutter) and not sure if that'll be too fast for 1/2200th flash duration (t0.5).

Thank in advance
Click to expand...

No, it's not that simple, but ball-park 3x won't be far off. You'll not get any closer than that without doing oscilloscope tests. You have then got to convert t.1 to an actual shutter speed equivalent, and again that's not something you can calculate. Or at least, there is no existing formula for it that I know of, though I believe you could create one (but that's another story - and a lot of testing). Being more helpful, my experience is if you take t.5 x3 you'll be there or thereabouts for a shutter speed equivalent at higher power settings, or t.5 x2 for lower outputs if that's given. This is for voltage-regulated conventional studio-type heads; IGBT is completely different and at anything except max output, t.5, t.1 and actual shutter speeds are pretty much the same thing.

Leaf shutters do strange things at top speed, and the blades open in different shapes/patterns, but in fairly crude terms they are always open for longer at the centre than the edges. This doesn't create so much of a vignetting effect, but more a depth-of-field effect over the whole of the frame. Basically for part of the exposure, the shutter is acting like an aperture diaphragm that increases DoF and reduces total exposure. Luckily, to compensate for exposure loss, they very rarely run at anything too near the claimed top speed ;)
 
HoppyUK said:
This is for voltage-regulated conventional studio-type heads; IGBT is completely different and at anything except max output, t.5, t.1 and actual shutter speeds are pretty much the same thing.
Click to expand...

So just to clarify, an IGBT unit like the Profoto B1 which quotes a flash duration of 1/1000th at max power, wouldn't actually equate to 1/1000th shutter speed, because its at full power?
If that's correct, at what point does the flash duration and shutter speed come into line?
If that makes any sense? (n)
 
treeman said:
So just to clarify, an IGBT unit like the Profoto B1 which quotes a flash duration of 1/1000th at max power, wouldn't actually equate to 1/1000th shutter speed, because its at full power?
If that's correct, at what point does the flash duration and shutter speed come into line?
If that makes any sense? (n)
Click to expand...

Profoto tend to quote t.5 which can be quite misleading

Mike
 
treeman said:
So just to clarify, an IGBT unit like the Profoto B1 which quotes a flash duration of 1/1000th at max power, wouldn't actually equate to 1/1000th shutter speed, because its at full power?
If that's correct, at what point does the flash duration and shutter speed come into line?
If that makes any sense? (n)
Click to expand...
For most IGBT's that I have seen numbers for, at full power t0.1 is ~ 1/2 of t0.5. By around ~ 1/4pwr t0.1 and t0.5 line up closely. And then they split again towards minimum power (~ 1/64). And the speeds are faster as the power is reduced.

Non-IGBT's tend to keep roughly the same spread (~1/3) across all power settings and are "fastest" at full power.
 
Last edited:
sk66 said:
For most IGBT's that I have seen numbers for, at full power t0.1 is ~ 1/2 of t0.5. By around ~ 1/4pwr t0.1 and t0.5 line up closely. And then they split again towards minimum power (~ 1/64). And the speeds are faster as the power is reduced.
Click to expand...

Thanks Steven, that makes sense.
I'm going to try it out 'real world' in a couple of weeks time, with an MF camera syncing at 1/800th sec, hopefully still catching all the flash at full power. Sounds like the B1 may struggle but I'm hoping the B3 (t0.5 flash duration 1/3000 at full power) should work fine. I just wanted to check whether I wasn't completely wasting my time, before I made the trip up to Hasselblad.
 
treeman said:
So just to clarify, an IGBT unit like the Profoto B1 which quotes a flash duration of 1/1000th at max power, wouldn't actually equate to 1/1000th shutter speed, because its at full power?
If that's correct, at what point does the flash duration and shutter speed come into line?
If that makes any sense? (n)
Click to expand...

As Steven says really. I've tested the B1 and in 'freeze' mode estimated flash duration at full power equating to 1/500sec shutter speed. Thereafter the flash duration pretty much halves with every halving of power output, in line with general IGBT practise.
 
HoppyUK said:
As Steven says really. I've tested the B1 and in 'freeze' mode estimated flash duration at full power equating to 1/500sec shutter speed. Thereafter the flash duration pretty much halves with every halving of power output, in line with general IGBT practise.
Click to expand...
Just out of interest Richard, in doing your tests do you use cables to trigger or wireless? Or does it not make any difference?
 
treeman said:
Just out of interest Richard, in doing your tests do you use cables to trigger or wireless? Or does it not make any difference?
Click to expand...

I never use cables. Triggers are very fast these days so it doesn't really matter, and the only time it might matter is if you were testing max x-sync speed of the camera, and I'm not doing that. My default shutter speed is 1/125sec, which is long enough to cover any delays while making sure 100% of the flash output is captured. Some flash features only work with a dedicated trigger, HSS for example, so I obviously use whatever is appropriate.
 
treeman said:
Thanks Steven, that makes sense.
I'm going to try it out 'real world' in a couple of weeks time, with an MF camera syncing at 1/800th sec, hopefully still catching all the flash at full power. Sounds like the B1 may struggle but I'm hoping the B3 (t0.5 flash duration 1/3000 at full power) should work fine. I just wanted to check whether I wasn't completely wasting my time, before I made the trip up to Hasselblad.
Click to expand...

Just had a play with my B1 and Fuji X100s which has a leaf shutter. 1/500th was as fast as I could sync without losing light. At 1/800th you lose about 1/3 stop
 
sk66 said:
*With the Fuji x100s.* The leaf shutter in a compact/P&S is a bit different animal compared to the leaf shutter in a MF lens... Not better/worse, but probably not directly comparable.
Click to expand...

Same principle, mechanically a bit different, but similar result. What's not comparable?
 
HoppyUK said:
Same principle, mechanically a bit different, but similar result. What's not comparable?
Click to expand...
I'd say that size is a significant factor, mechanically speaking, moving the leaves at the same speed becomes an issue. Though I do appreciate MF mfrs have more money to throw at the problem.
 
matty D said:
Just had a play with my B1 and Fuji X100s which has a leaf shutter. 1/500th was as fast as I could sync without losing light. At 1/800th you lose about 1/3 stop
Click to expand...


But do you lose that light evenly across the frame?

As I have previously said Profoto quote the t.5 time and there is still light coming out so at full power the the light pulse is much closer to 1/300 so at full power using speeds above that you should expect a reduction in power. Those nice guys at Godox quote t.1 times which is far better to help you answer such questions.

If you turn the power of the B1 to 1/2 or 1/4 you should see much lees or possibly no light drop off at max sync speed.

Mike
 
mike weeks said:
But do you lose that light evenly across the frame?
Click to expand...

That's what should happen with a leaf-type shutter. I should have added in post #9 above that the unusual imaging effects of leaf shutters only show up at both max speed, and also at max aperture.

As I have previously said Profoto quote the t.5 time and there is still light coming out so at full power the the light pulse is much closer to 1/300 so at full power using speeds above that you should expect a reduction in power. Those nice guys at Godox quote t.1 times which is far better to help you answer such questions.
Click to expand...

True, but the lion's share of total brightness will be within the t.5 time.

If you turn the power of the B1 to 1/2 or 1/4 you should see much lees or possibly no light drop off at max sync speed.

Mike
Click to expand...

Yes :)
 
HoppyUK said:
True, but the lion's share of total brightness will be within the t.5 time.
Click to expand...

But it does explain

matty D said:
Just had a play with my B1 and Fuji X100s which has a leaf shutter. 1/500th was as fast as I could sync without losing light. At 1/800th you lose about 1/3 stop
Click to expand...

Mike
 
HoppyUK said:
Same principle, mechanically a bit different, but similar result. What's not comparable?
Click to expand...
MF leaf shutters operate the same as an aperture diaphragm and is also located in the lens. And as we all know, a smaller lens opening (aperture) doesn't reduce the size of the projected image circle. So while a MF leaf shutter is closing down and "restricting" light, it's not physically "blocking" the sensor as such (or as significantly).

The leaf shutter in a P&S/compact is generally one or two blades that wipe across the sensor in the camera body... the Fuji X100s uses two that meet in the middle. This is much more similar to the typical shutter curtain character in operation, and it is physically blocking areas of the sensor from light the instant it starts to move.

That's my understanding of it anyway...
 
Last edited:
sk66 said:
MF leaf shutters operate the same as an aperture diaphragm and is also located in the lens. And as we all know, a smaller lens opening (aperture) doesn't reduce the size of the projected image circle. So while a MF leaf shutter is closing down and "restricting" light, it's not physically "blocking" the sensor as such (or as significantly).

The leaf shutter in a P&S/compact is generally one or two blades that wipe across the sensor in the camera body... the Fuji X100s uses two that meet in the middle. This is much more similar to the typical shutter curtain character in operation, and it is physically blocking areas of the sensor from light the instant it starts to move.

That's my understanding of it anyway...
Click to expand...

Fuji X100 has an in-lens shutter, that should behave something like a leaf-shutter, though trying to find out exactly what's going on inside most compacts is pretty much impossible. I've searched for more info several times, but it seems details are never given.

Specifically on the X100 though, DPReview did some tests a few years ago to illustrate the strange goings on at fast shutter speeds and max aperture, here (scroll down a bit): http://www.dpreview.com/reviews/fujifilmx100/17
 
HoppyUK said:
Specifically on the X100 though, DPReview did some tests a few years ago to illustrate the strange goings on at fast shutter speeds and max aperture, here (scroll down a bit): http://www.dpreview.com/reviews/fujifilmx100/17
Click to expand...
That seems a particularly odd design for an in-lens shutter. Interesting that it's only 1/500 and below that the entire aperture is cleared... that correlates to the 1/500 that Matt noted.
 
Last edited:
When I get to have a play with the Hassy, my plan is to try it out on both my B1 and B3. I’ll put them (one at a time) on full power, set shutter speed on the camera body to 1/200th sec, then just stop down till my subject is exposed correctly. I’ll then increase shutter speed until my subject shows any sign of underexposure. Anyone see any flaws in that plan? My only concern is whether the delay in the wireless trigger will have an effect?

I’m guessing, by whats been said so far, the B1 will be fine up to 1/500th sec without any light loss, and hoping the B3 will be fine all the way up to 1/800th sec. If it does, I’ll effectively be overpowering the sun by an extra two stops compared to my Nikon gear.
 
I may be wrong Mark, but I seem to recall seeing some extreme sports togs using Phase One, and being able to sync up to 1/1600. Might be something to consider, and probably cheaper than Hassy??
 
matty D said:
I may be wrong Mark, but I seem to recall seeing some extreme sports togs using Phase One, and being able to sync up to 1/1600. Might be something to consider, and probably cheaper than Hassy??
Click to expand...

It was noticed in the Sanity check thread that they said they (A phase one user) had gone into HSS at 1/500 (or similar) with the issue being that yes they should be able to normal sync at up to 1/1600

Mike
 
treeman said:
When I get to have a play with the Hassy, my plan is to try it out on both my B1 and B3. I’ll put them (one at a time) on full power, set shutter speed on the camera body to 1/200th sec, then just stop down till my subject is exposed correctly. I’ll then increase shutter speed until my subject shows any sign of underexposure. Anyone see any flaws in that plan? My only concern is whether the delay in the wireless trigger will have an effect?

I’m guessing, by whats been said so far, the B1 will be fine up to 1/500th sec without any light loss, and hoping the B3 will be fine all the way up to 1/800th sec. If it does, I’ll effectively be overpowering the sun by an extra two stops compared to my Nikon gear.
Click to expand...

If you're wanting to know how fast you can run before the shutter begins to reduce brightness, yes. But anything less than a very fast trigger will reduce that, and to prevent natural lens vignetting skewing things at different apertures, only compare the centre and preferably at mid-range f/numbers.
 
matty D said:
I may be wrong Mark, but I seem to recall seeing some extreme sports togs using Phase One, and being able to sync up to 1/1600. Might be something to consider, and probably cheaper than Hassy??
Click to expand...

mike weeks said:
It was noticed in the Sanity check thread that they said they (A phase one user) had gone into HSS at 1/500 (or similar) with the issue being that yes they should be able to normal sync at up to 1/1600

Mike
Click to expand...

Yes,one of the selling points of the Phase One is the faster flash sync speed, but I'd be quite happy if I can just gain an extra couple of stops, so an 1/800th sec top sync speed is fine for my needs, not to mention the Phase One is a lot more expensive, like £6K more !!
 
HoppyUK said:
If you're wanting to know how fast you can run before the shutter begins to reduce brightness, yes. But anything less than a very fast trigger will reduce that, and to prevent natural lens vignetting skewing things at different apertures, only compare the centre and preferably at mid-range f/numbers.
Click to expand...

Thanks Richard.
 
You must log in or register to reply here.
Back
Top