oh yes, balls are the way to do it

or the use of styrofoam balls to evaluate light sources.

After thinking about ways to evaluate softboxes, brollies and the like, I decided to try polystyrene balls as a target to better see what is going on and it works really well.

 Here is a set of balls I got from hobbycraft - middle sized and big ones alternating - hanging in front a bare naked flash (Yongnuo 565), set to 24mm with the diffuser in place.

The balls are all lit with a hard edge around the circumference of each ball, there is a little reflected light showing from the white ceiling and other balls, but not enought to matter really. Below is a zoom in on the centre 3 balls.

lightbox mods - illumination

Here's some shots of the illumination from the original and modded Lastolite hotrod.

Placed on the floor angled up at approx 45 degrees with the nearest part of the box 12" from the surface.

	flat black background	curtains
original
modded

The modded version gives a better spread along the length and also gives a more wrap-around light, particularly near the center (which is what you would expect)

more details on Lastolite hotrod strip mods

Pretty basic really, here's a couple of photos of what I've done inside: (Colour balance is weird as under led lamps and not adjusted). Also I've set the box horizontal 'cos it is easier to work with and photo while messing about.

This first shot shows the original internal baffle, which I have folded in the middle to shorten it, temporarily attached with peelable tape.  I folded the middle section (which is double thickness into 3.  This allows some light from the flash & reflector to leak directly to the ends of the front diffuser.

Removing the inner diffuser (now lying on the bottom) shows the prism reflector in place.

and here is a shot with the prism reflector also removed.  The flash is a Canon 270Ex II sitting on top of a pixel king, and set to tele mode (front element pulled forward).  I'll give it a go with some other flashes ion a day or 2 to see how it behaves.

The prism is 2 pieces of card 10cm wide the joined edges are 15.5cm long (which allows it to fit snuggly up against the hot shoe mount ring) and the edges nearest the front of the box are 17cm. They are at an angle of 85 degrees.

It's held in place for now with a couple of small strips of blu-tack to the top and bottom faces.

I made the prism with card covered in aluminium foil - probably easier to use silver mirror card if you have it to hand _ did think it might be necessary to crumple the foil slightly, but this doesn't seem to be needed.

Lastolite hot-rod strip review and mod

Finally decided on a hot-rod strip as the long softbox to get - there are a few positive reviews out there like this and this (which is really a video review), and no negative ones I found.
As regards general use and assembly these reviews are good, but I soon noticed that if the box is close to the subject it has a tendency to give a 'hot middle'.  You can also see this in the photo's of Sarah in the first review.  Indeed the reviewer says "At close range the illumination starts to fall off in a full length shot. So here the the feet are underexposed." In fact imho the central part is tending to overexposed - in both the full length and the 3/4 shot. A quick photo of the box itself shows why this isn't really surprising.There is a big fall off from the centre to the ends of the box. In fact looking at the histogram shows there is just over 2 stops drop off from the centre to the ends.

This may not be a problem, depending on how you will be using the box, but it does constrain how close you can place the box the the subject - and normally you want to get the box as close as practical both to increase the effectiveness of the box, and to reduce the power needed (we are talking battery flashes here after all).

So I wondered if it would be practical to improve this situation. Here is the result of an afternoons messing about with silver foil and fabric stiffener.

A big improvement, confirmed by the histogram below.  Now we have about 0.8 stop variation in output along the length of the box.  And yes - this does make for more even lighting when the flash is close to the subject.

I'll publish info on how to do this tomorrow.

I've also added some piccies of the illumination from the original and modded versions here