Oscilloscopes

[HoppyUK]

Question for electronics people really.

I know nothing about oscilloscopes, but thinking about getting one for my work - I want to measure flash durations, and also colour temperature, and have a couple of questions. With flash durations, ideally it needs to be accurate to something like 1/50,000sec or better and I'm wondering whether the important thing here is the probe rather than the oscilloscope itself? Is it possible to measure colour temperature, or even better, to show how colour changes throughout the flash burn?

Any recommendations and price guidance welcome If I need summat fancy, I could hire as I'd only need it a few times a year when testing flash kit.

 

[Digisatman]

have a read

https://www.photigy.com/paul-c-buff...duration-test-action-v-s-constant-color-mode/

 

[chuckles]

Most oscilloscopes will handle the duration - a bog standard 'scope usually resolves 2Mhz clock. As you've rightly identified the I/F from received light to 'scope is going to be your first hurdle. Not too difficult to achieve with fast switching electronics. Your biggest and most expensive problem is the colour temperature part. Not insurmountable but will prove costly I suspect.

 

[HoppyUK]

have a read

https://www.photigy.com/paul-c-buff...duration-test-action-v-s-constant-color-mode/

Thanks Shaun, I've been using the spinning disc method for estimating 'effective' flash durations vs actual shutter speeds for a few years now. Got it down to quite a fine art, and the results are certainly better than the industry's t.5 and t.1 times calculated with an oscilloscope. But the problem with t.5 times etc is not the oscilloscope, but the t.5 calculation formula that is a) easy, but too crude, and b) bears no relation to real, effective flash duration times with most studio flash (ie not IGBT).

However, the true answer has to be in those oscilloscope traces somewhere, it just needs the right formula that better matches reality. That's what I want to have a go at.

Most oscilloscopes will handle the duration - a bog standard 'scope usually resolves 2Mhz clock. As you've rightly identified the I/F from received light to 'scope is going to be your first hurdle. Not too difficult to achieve with fast switching electronics. Your biggest and most expensive problem is the colour temperature part. Not insurmountable but will prove costly I suspect.

Thanks. If you know of any specific products I could check out, that would be a great help

 

[Garry Edwards]

Most oscilloscopes will handle the duration - a bog standard 'scope usually resolves 2Mhz clock. As you've rightly identified the I/F from received light to 'scope is going to be your first hurdle. Not too difficult to achieve with fast switching electronics. Your biggest and most expensive problem is the colour temperature part. Not insurmountable but will prove costly I suspect.

From my own tests of different oscilloscopes (not comprehensive but better than nothing) most can't accurately measure flash durations shorter than around 1/5400th.
The first one we bought certainly couldn't, it didn't matter at the time because this was before the days of IGBT studio flash, we now have a very high end one that is fine with very short flash durations.

As for measuring colour temperature, I use the Minolta colour temperature meter, in fact I have 2 of them, one backs up the other and is used to verify the readings of the other, and the readings are usually too close to identical to matter. These meters are designed for flash but can also be used for continuous lighting, although their readings can be a bit off with discontinuous spectrum lighting, especially when it comes from LEDs.
I don't know whether an oscilloscope is capable of measuring colour temperature.. If it is, then I don't know how to do it and wouldn't bother trying, as the Minolta produces spot on readings without effort.

 

[HoppyUK]

Thanks Garry. I was hoping you'd respond

No cheap and easy answers then. I might just continue the way I am, as the methods I currently use have some real advantages and there are a few improvements I can make. The main problem is it's laborious, both setting up, using, and then interpreting the results, but it's not something I do every day.

 

[Garry Edwards]

Thanks Garry. I was hoping you'd respond

No cheap and easy answers then. I might just continue the way I am, as the methods I currently use have some real advantages and there are a few improvements I can make. The main problem is it's laborious, both setting up, using, and then interpreting the results, but it's not something I do every day.

Yes, well, maybe it's best to put it on the back burner for now.
I'm sure that we'll see you at "Lencarta Towers" again, and when that happens I'll be happy to show you both our oscilloscope and our colour temperature meters, which will put you in a better position to decide on the way forward.

I think we're the only people who actually test both flash durations and colour temperature.. Even if we felt able to trust factory figures (which we know from experience not to) because our products are different from the factory base models, we have to test them ourselves. Because of this we've had to learn how to do it ourselves.

 

[HoppyUK]

Yes, well, maybe it's best to put it on the back burner for now.
I'm sure that we'll see you at "Lencarta Towers" again, and when that happens I'll be happy to show you both our oscilloscope and our colour temperature meters, which will put you in a better position to decide on the way forward.

I think we're the only people who actually test both flash durations and colour temperature.. Even if we felt able to trust factory figures (which we know from experience not to) because our products are different from the factory base models, we have to test them ourselves. Because of this we've had to learn how to do it ourselves.

 

[Steve T]

Yes, well, maybe it's best to put it on the back burner for now.
I'm sure that we'll see you at "Lencarta Towers" again, and when that happens I'll be happy to show you both our oscilloscope and our colour temperature meters, which will put you in a better position to decide on the way forward.

I think we're the only people who actually test both flash durations and colour temperature.. Even if we felt able to trust factory figures (which we know from experience not to) because our products are different from the factory base models, we have to test them ourselves. Because of this we've had to learn how to do it ourselves.

Thats how it should be, if you care that is