How many stops will I gain going from 650 to 1000ws?

Anyone know?

every time you double the power you gain a stop so theoretically almost 1

but that depends on the efficiency of the strobes and if they're producing that much light or just using that much power...

unferth wrote in post #5790166
every time you double the power you gain a stop so theoretically almost 1

but that depends on the efficiency of the strobes and if they're producing that much light or just using that much power...

So basically from F11 I can shoot at F16 so + another 350ws I can shoot say... F20?

M Powered wrote in post #5790207
So basically from F11 I can shoot at F16 so + another 350ws I can shoot say... F20?

No.

You need to double the power (theoretically) for each additional stop.

So if you can shoot at f/11 with 650ws, you would need 1300ws to shoot at f/16, 2600ws to shoot at f/22, 5200ws to shoot at f/32, etc.

This assumes all other factors are equal, including efficiency of the strobes, same modifiers, same distance, etc.

All else being equal, going from 650 to 1000 ws should get you from F11 to F14 (2/3rd stop) but to go from f11 -> f20 you'd need 1 2/3rd more stops from f11 so..

650 * 2= 1300 (one stop)
1300 * 1.6 = 2200 (or so).. so you'd need a whole pile of power

Can someone enlighten me as to why one would need/want to shoot a model at f/16 or f/22? How much DoF does one need anyway? I can understand that if shooting portraits, it is sometimes desirable to shoot with a shallow DoF.

ebann wrote in post #5790329
Can someone enlighten me as to why one would need/want to shoot a model at f/16 or f/22? How much DoF does one need anyway? I can understand that if shooting portraits, it is sometimes desirable to shoot with a shallow DoF.

In order to properly expose a sunny background at X-sync speed (1/250), you'll need to be around f/10 at ISO 100. If you wanted to underexpose the background (for artistic reasons), you will need to stop down from there.

ebann wrote in post #5790329
Can someone enlighten me as to why one would need/want to shoot a model at f/16 or f/22? How much DoF does one need anyway? I can understand that if shooting portraits, it is sometimes desirable to shoot with a shallow DoF.

To overpower the Sun. Slap on small/ medium diffuser and you'll end up not having enough power.

goto www.rrpix.com and look at his beach collection. Want to guess how much juice you need for something like that? My guess would be 2500ws

Curtis N wrote in post #5790359
In order to properly expose a sunny background at X-sync speed (1/250), you'll need to be around f/10 at ISO 100. If you wanted to underexpose the background (for artistic reasons), you will need to stop down from there.

I was going to ask "Why would one need more light on a sunny day?" when I read the next post...

M Powered wrote in post #5790437
To overpower the Sun. Slap on small/ medium diffuser and you'll end up not having enough power.

goto www.rrpix.com and look at his beach collection. Want to guess how much juice you need for something like that? My guess would be 2500ws

That is an interesting and non-obvious concept! More light needed on a sunny day! Unless it's the old fill-in flash we're talking about?

Is it right to conclude that a studio would require far less power since there is no sun to overpower?

ebann wrote in post #5790479
I was going to ask "Why would one need more light on a sunny day?" when I read the next post...


That is an interesting and non-obvious concept! More light needed on a sunny day!

Is it right to conclude that a studio would require far less power since there is no sun to overpower?

Yea, its very ironic, need more light for a sunny day

Meter the sky and shoot the model on a bright day, the model will be almost completely dark. Now take that and drop the sky by 2-3 stops... now figure out how much juice you will need to light the model Depending on your lens, you might need to slap on a 2 stop ND filter.

Your average size studio you will probably wouldn't need anything more than 300ws.

a side question, how much power does a EX580 II give you?

Galaxy99 wrote in post #5790688
a side question, how much power does a EX580 II give you?

From photo.net:

"Matt K , Dec 19, 2005; 04:31 p.m. As mentioned, it will depend on the zoom setting. Also, watt/seconds is not the most accurate/consistent way to judge power output.
That said, I have a 580EX and a Lumedyne kit. I've compared the two directly under the same conditions...
With 580EX set to full manual at 35mm zoom setting and no modifiers, I get a reading of about f/8, ISO 100 at about 10 feet.
With a Lumedyne 067 400WS pack with one head with just a reflector in the normal position, I get a reading of about f/16, ISO 100 at 10'
So given that, the 580EX is about 2 stops lower than my 067 Lumedyne, or "roughly" 100WS. Not bad for a shoe-mount flash. But adding any modifiers and/or widening the zoom coverage and it can become limiting depending on what your subject is."

Wouldn't make a dent in overpowering the sun...

http://photo.net …a-fetch-msg?msg_id=00EZNc

so... about 100ws or so for a 58 gn size flash.. (580ex, Metz 58's , etc.)

Galaxy99 wrote in post #5790688
a side question, how much power does a EX580 II give you?

My estimate is lower than those above. compared to an Alienbees B1600 and fired into the same umbrella, I calculate about 40 ws.

Curtis N wrote in post #5790792
My estimate is lower than those above. compared to an Alienbees B1600 and fired into the same umbrella, I calculate about 40 ws.

Thats it??? just a measly 40ws?