Major differences strobes 150w vs 800w or more

[Gundus]

I know ist's a stupid question, but what is th main difference in image terms between a 150w strobe and a 600w or more strobe.

It's a softer light? What you can do with a 600w strobe that a 150w can't do?

Thank you in advance

 

[Ian Grant]

The amount of power affects the choice of f stop, lower power will be more limiting, so where a 150W may give f5.6 the 600W is likely to have a greater range of adjustment and be usable at f16.

Ian

 

[aluncrockford]

If the flash tube is the same or similar size then the only difference is intensity not quality, the diffusion of the light is what causes the quality to change, for instance putting the light through perspex will soften the light regardless of the power of the flash, though it is fair to say the higher the output the greater the options, it is very easy to turn the power down, and multi flashing to increase output is not entirely practical

 

[David A. Goldfarb]

The Watt-second rating (not Watt, but Watt-seconds) of a strobe refers to the amount of energy put into the head, and doesn't precisely correlate to the amount of light output, which depends on the efficiency of the head, and the reflector and/or diffuser being used. You can use Watt-seconds to compare relative output between heads of the same model, so through the same head 800 W-s will be one stop brighter than 400 W-s, but when comparing units of different manufacture, it's only a rough guide.

 

[jerry lebens]

Ian and Alun are both correct and, by adding their contributions together, you reach yet another significant conclusion...

As Ian says increasing the output gives a greater range of useable aperture settings (allowing you a greater set of options in depth of field).

And, as Alun says, softness is created by diffusion (or reflection). Diffusion means spreading the output of your light over a greater surface area (hence the sheet of perspex or softbox or umbrella).

Unfortunately, diffusion absorbs power. If you use a diffuser, you'll need much more power to achieve the same aperture than you would with a bare, non-diffused, flash head.

So, if you want soft lighting for portraits, say, you'll probably need more power - especially if you want lots of depth of field at the same time.

Regards
Jerry

 

[Ian C]

When comparing the stored energy rating for studio flash units, you might also want to know that the SI unit of energy, the joule, is precisely the same as the watt-second.

In the US the watt-second ratings are more common, while European-made units usually are rated in joules.

http://en.wikipedia.org/wiki/Joule

 

[Ian Grant]

Adding to what Jerry's just said I had a 150W flash head mid 1970's it was just feasible to shoot full length model shots at about f4 through a diffuser. A couple of years later I had constant access to a few larger 1.5k & 3k flash packs but bought a pair of 500w heads for portability.

Now I still use those 500W heads alongside my main 800w head, but the 800w head gives me far greater flexibility, the old 150W head just gets a quick test every few years now. If I need more power I borrow or hire as needed.

Flash heads usually have a good lifespan, I'd guess my Elinchroms are 30+ years old now and still perform well. So get the best in terms of power you can afford.

Ian

 

[Gundus]

Thank you guys...it makes sense the conclusion!