Ws and GN's
- Thread starter JSER
- Start date
- Messages
- 26,617
- Edit My Images
- Yes
I don't think there is because they're two very different things. The Guide No.is an indication of the power output of the flash, while Watts - second is simply an indication of how much power the capacitor in the flash is capable of delivering to the flash head.
The GN is affected by many variables such as the size of the reflector, any soft boxes or diffusers used and the reflectivity (lightness or darkness) of the subject, so it's only a rough guide as to correct exposure in any practical situation, while the Ws is, in theory anyway, a fixed value.
I suppose if you were always shooting at a constant distance with the same flash setup and identical reflectivity in your subject, you could come up with some correlation between the two things, but it's an unlikely scenario and I struggle to see much mileage in stressing the grey matter too much about it.
The GN is affected by many variables such as the size of the reflector, any soft boxes or diffusers used and the reflectivity (lightness or darkness) of the subject, so it's only a rough guide as to correct exposure in any practical situation, while the Ws is, in theory anyway, a fixed value.
I suppose if you were always shooting at a constant distance with the same flash setup and identical reflectivity in your subject, you could come up with some correlation between the two things, but it's an unlikely scenario and I struggle to see much mileage in stressing the grey matter too much about it.
HoppyUK
Suspended / Banned
- Messages
- 23,200
- Name
- Richard
- Edit My Images
- No
As CT says, you can't compare them directly. Furthermore, you have to be pretty careful comparing GNs with GNs and WSs with WSs. Both are areas where there are no laid down standards and some manufacturers interpret them differently or use weasel words like 'equivalent watt-seconds' to make their products sound good.
Maybe this helps. I reckon my Canon 580EX guns work out at around 80Ws at full power. By equalising everything as much as possible (ie reverse firing both into an identical softbox) that's the rough equivalent compared to my 200Ws Elinchrom D-Lites.
This figure relates quite closely to similar tests others have done with big high-end hot shoe guns.
Edit: not sure what you're trying to do, but as a comment I find that power, or lack of, is not usally an issue with hot shoe guns if you're using them for basic home portraiture or something fairly simple like that. I rarely have my D-Lites on full power. The difference is studio heads recycle almost instantly compared to a few seconds for a hot shoe gun at full power, which I find to be vital with fast moving expressions, and of course you have the major benefit of the modelling light. And studio heads are pretty cheap at the end of the day.
Maybe this helps. I reckon my Canon 580EX guns work out at around 80Ws at full power. By equalising everything as much as possible (ie reverse firing both into an identical softbox) that's the rough equivalent compared to my 200Ws Elinchrom D-Lites.
This figure relates quite closely to similar tests others have done with big high-end hot shoe guns.
Edit: not sure what you're trying to do, but as a comment I find that power, or lack of, is not usally an issue with hot shoe guns if you're using them for basic home portraiture or something fairly simple like that. I rarely have my D-Lites on full power. The difference is studio heads recycle almost instantly compared to a few seconds for a hot shoe gun at full power, which I find to be vital with fast moving expressions, and of course you have the major benefit of the modelling light. And studio heads are pretty cheap at the end of the day.
Last edited:
Yes, being a 50+ photographer I know it is not as simple as we would all like, so thanks for that.
What I was considering is, a 250Ws head, for nature use rather or as well as my Metz 45 CL-4, and simply wanted to calculate a simple comparison.
If in a VERY simple form the Metz was say on a power scale od 1-100 a 40, then I wondered what this would be.
http://www.calumetphoto.co.uk/eng/product/calumet_genesis_300b_flash_head/cf0507
What I was considering is, a 250Ws head, for nature use rather or as well as my Metz 45 CL-4, and simply wanted to calculate a simple comparison.
If in a VERY simple form the Metz was say on a power scale od 1-100 a 40, then I wondered what this would be.
http://www.calumetphoto.co.uk/eng/product/calumet_genesis_300b_flash_head/cf0507
HoppyUK
Suspended / Banned
- Messages
- 23,200
- Name
- Richard
- Edit My Images
- No
Hard to say. Your Metz is a big old beast and the first problem is that the headline GN is only 45. However, that's for fixed 35mm lens coverage and when that's converted to the 105mm equivalent quoted for a Canon 580EXII, you're probably looking at GN70 or 80 (guess!). It's certainly more powerful in terms of total light output.
So, using a bit more educated guesswork, I would say the Genesis 300 would be at least one stop brighter, more likely two. But that kind of order.
For wildlife, a lot of folks use a Better Beamer attachment, or a Kirk Flash X-tender. It adds a couple of stops with a 300mm lens, basically doubles the range.