Industry News: Hasselblad announces the X1D II 50C medium format camera, and the XCD 35-75 zoom lens

[Kit.]

If I look at this document here, total power density of solar radiation at earth surface is about 1.35 kW/m2,

No, that's the value for the upper atmosphere.

of which 520 W/m2 fall into the visible range. This would suggest an efficiency of about 38.5%.

No, it wouldn't, if the efficiency is measured against monochromatic green light. It would, if the efficiency is measured against an ideal white source emulating just Sun's visible spectrum, but then the efficiency of the tungsten and flash light should be increased accordingly.

This efficiency is a lot higher than an ideal black body radiator would theoretically give,

Haven't you noticed that the values you are quoting are the values for the Sun's ideal black body radiator model?

So, you are actually claiming that this model provides "a lot higher" efficiency than it should. Sounds self-contradictory. Maybe you are mistaken?

So where does this lead us? In order to get 520 W/m2 visible light power with photo flood lights, we need about 10.000 W of incandescent light shone into 1 m2.

No, and strobe light isn't even incandescent. It has a similar spectrum to sunlight in visible range, but it contains much more ultraviolet, which reduces its luminous efficiency compared to sunlight.

If a decent strobe outputs 200J within 1/2000s, its effective light power equals 400.000 W, which is much stronger than sunlight. You could use one strobe to illuminate a circle of 7m diameter and are still as powerful as direct sunlight hitting at 0° angle off the surface normal.

You can twist and turn this over again and again: even if you throw a factor of 2 or 3 into this to cover some additional inefficiency, it is quite possible to match direct sunlight with portable strobes. If optimal depth of field suggests largest possible aperture, then very short sync times can be a benefit to those who want to take advantage of it and who can afford such a toy.

You don't need to twist or turn anything. If you are still confused about relative sunlight and strobe light efficiency, you can cross-check it using more photographer-friendly numbers: flash GNs.

For example, my 550EX has GN9 at 80mm at 1/2000 HSS, which means that for Sunny-16 shooting at 1/2000 it gives at -1EV fill at 3.2m and -2EV fill at 4.5m at full power, which is already usable.

But of course, it would be much more usable if one could use it in non-HSS mode, where GN9 at 80mm is only 1/32 of its power.

 

[Rudeofus]

So basically we have a whole pile of unknowns with sunlight, we have a comparable pile of unknowns with flash light, my numbers may be off by some factor 2 or 3 or whatever, and we still arrive at the same conclusion:

1. a flash can be used to balance out sunlight in HSS mode, and could be used much better in non-HSS mode.
2. there are flashes which output a significant part of their light within 1/2000s and it would be nice to have a camera+flash which can do this properly