ok at uni we had gemini 1000 studio heads but very rarely if ever used them on full power as they where loud and ridiculously bright - my question is how much power do most studios require ? ive found some gemini 200 but not sure if they would not be powerfull enough
It does depend on what and where you intend using them for, but generally speaking err on the powerful side. I use 2xProfoto 600W as main lights and 2 x Bowens 400W as 3rd/4th lights. By using higher power lights but at reduced power, you reduce the recycle time compared to using lower power lights running at full power all the time. It also gives you smaller working apertures if you need them, as well as allowing more flexibility in positioning lights.
So in short, I would suggest a minimum of 400/500W lights, 1000W probably not necessary.
Better to have too much power than not enough....once you add barn doors etc the weaker heads will struggle.
That said, there is some value in having at least one lower powered head in case you want to bring the light source close to the model for harder shadows....a high powered head even on minimum might be too much.
Personally I use ancient Courtenay heads (400W) and rarely set them to more that 25%.....but they are rarely more than a few feet from the model. I also have the next range up and never use them....even on minimum they are too powerful for my home studio but were ideal when I had a 20' x 40' space.
200s are around budget value and smaller spaces with simple ideas, 500s are much better with shoots, barndoors, gels etc, can be used in various conditions and as mentioned a above bigger flashes on low recycle quicker but come at a cost so its a case of weighing the pros and cons to your needs. Most studios ive used have had 2 250s, couple 500s and not often 1000 unless it was a big space.
Depending on how you modify your lighting, 500w should be more than enough for 99% of studio situations.
It's probably best to buy more power than you need....so that you don't have to use your flash set to full power...resulting in quick recycle times & better stability between frames.
Having said that...I have a 1000w strobe that, on occasion, I have to use close to full power....but I modify that bad boy like crazy.
Elinchrom used to have the guide numbers for their heads and also light reduction factors for their various modifiers in their downloadable PDF catalogues (unsure if they still do). From this you can calculate some approximate values of what you need/can use for whatever size of room and type of modifier used.
As has been said it is going to depend on a number of factors. the size of the studio only indirectly effects things in that with a small studio with white walls you will get some bounce back.
The other considerations are the aperture you wish to shoot at, the light modifiers you use, the type of lighting you are seeking to achieve, the ISO you are using
On that score bigger is not always better as suggested above. You may well find that even 500W units are too powerful in some situations where you want a large aperture. For example with Boudoir I prefer to be at least f5.6-f3.5 Using a hard light with deep reflector and no grid I sometimes find myself using the smaller 250W units to achieve that. The 500W units cannot be powered down enough.
In general though I found 250W ample when shooting in a single garage years ago and my main 500W units cope with pretty much everything in my current studio on a day to day basis. If I could only have one Flash it would be a 500W unit by Bowens or Elincrom that has 5 stops of range. Some cheaper ones cannot be turned down as much
Not sure if the OP asked the right question...if the question should have been more like 'What flash units do people recommend for the following situations....' it might have led to more useful replies.
For example,it might suit an experienced photographer to jump right into a high end system....but equally, it might be better for a novice to look for a cheapish low end system with good resale values to practise with.
So something like Courtenay pro heads for example....they were top end in their day but now pretty cheap on eBay...very reliable...and zero depreciation (in fact mine are worth more than I paid).
You'll find 500W will be fine for most needs, unless you are shooting still life with flash and using a lot of bellows extension on large format (can remember one nasty set-up in college having only 250W units avaliable, with the modifiers gels and about 450mm of extension it took 8 full power bursts then 4 on top of that decreasing the output each time). . .
Not sure if the OP asked the right question...if the question should have been more like 'What flash units do people recommend for the following situations....' it might have led to more useful replies. For example,it might suit an experienced photographer to jump right into a high end system....but equally, it might be better for a novice to look for a cheapish low end system with good resale values to practise with. So something like Courtenay pro heads for example....they were top end in their day but now pretty cheap on eBay...very reliable...and zero depreciation (in fact mine are worth more than I paid).
well im used to using gemini 1000's so i would like to stick with gemini - just a general small to medium sized studio situation
I've looked at Profoto's website (simply because they quote output figures for every modifier) and taken a #technical-specification" target="_blank">3'x4' softbox as an example modifier, softboxes by their very nature sap a lot of power out of flash units and the size is representative of a typical studio box.
The figures quoted by Profoto are f32 @ 2m distance (ISO 100) using one of their 2400W heads, so by using the Guide Number formula here that gives a guide number of 64. If you wish to re-calculate for a different powered head it is a simple case of doubling or halving the power (in Watts) is equivalent to 1 stop of output difference, so in this case if we wanted an approximation for a 600W head we would have an equivalent of f16 instead which would then equate to a guide number of 32 (ie. 2400W -> 600W is two stops).
Now, say we have a studio which you have a distance of 6m from flash to subject for example, all you have to do is simply put that f16 back through the guide number formula and you'll get a figure for what f/number your flash unit will be capable of. In this case a 600W head at 6m would only give an f/number of ~f5.6 (actually f5.333 through the formula), which IMO would be somewhat underpowered. If it were indeed f8 you were aiming for then you'd need a 1200W head, or f11 would need a 2400W head etc.
See, it's not rocket science to do this using numbers rather than 'opinions'.