Monday, 28 January 2013

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.

Saturday, 26 January 2013

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.Photo of the strip box showing eveness of illuminationThere 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

Sunday, 13 January 2013

2nd Curtain flash with Canon 7d and *various* kit

I got quite interested in using 2nd curtain flash recently, and have struggled to find out what is and isn't possible. Fortunately more is possible than I initially thought so here's what I have found.

Rule 1

You can only use 2nd curtain flash in 'local' mode - i.e. with Wireless func. disabled. This limits various things, like camera control of flash power by groups, but is by no means a show stopper, and certainly doesn't stop the use of off camera flash, or multiple flashes.

I'm only interested in manual use of flash.

So I haven't tried out anything related to auto flash things.


Things that work:

simplest use: built in flash plus extras

Using any flash fitted with an optical slave trigger, on camera flash can be turned down quite a bit (32nd works where other flashes to be triggered are within a few feet annd not too far off axis). Suck it and see.

I've done this with some studio flashes and using an old Soligor flash synchro unit which triggered an old Sunpack flash. (Can't even find an internet ref to the slave device, but it works well)

If the on camera flash is a problem, I switch to using Pixel Kings to do the first triggering.


MORE POWER: Canon flash in hotshoe

I can plug a speedlite into the camera hotshoe to get a bit more power or point the flash up for some bounce, and trigger further flashes optically as with the built-in flash.


Using a ttl flash extender cable

I've not done this myself, but this would be the logical next step if the length limitations aren't an issue (and a lot cheaper than wireless remotess..)


Using wireless (radio) remote triggers - Pixel Kings

 This gives slightly more control over at least a couple of flash units.

I have 2 Pixel King receivers working with 2 Canon 270EX IIs. The flash power of both can be set through the in-camera menu, but of course this sets both to the same power (but is still a lot better than nowt). Further flashes can of course be triggered from these if they use / are fitted with optical slaves.