Wednesday, 6 March 2013

Soft Boxes and Shadows

The collapsible soft box, especially those manufactured by Lastolite and numerous look-a-likes have grown in popularity with photographers, especially those working on location and fans of Strobist-style lighting and off-cameras flash.

The aim of this blog is provide a reference showing the effect of the light source and diffusion on your model, in this case the long suffering Fred who never protests or demands exorbitant fees when I overrun!

Click on images to view larger

For the purpose of this exercise I set the zoom on my flash to 50 mm. What one must bear in mind when using a Speedlite based soft box, the light emitted from the Speedlite projects forward with little beam spread to bounce off the reflective interior of the soft box, the majority of internal reflection is created by light bounced from the front diffusion panel.

In the frame above what you see is effectively an undiffused direct Speedlite creating a hard edge, dense shadow, with little or no influence from the soft box. The background is white plastic which has created a fill to the shadow under Fred's chin.


With the addition a white translucent Sto-Fen Omni-Bounce style diffuser the edge of the shadow benefits from the light spread created by the diffuser bouncing off the soft box interior.


With the Omni-Bounce removed and the soft box front white diffuser panel in place the light spreads making a broader softer edge shadow. As the flash is not diffused any internal reflection will be from light reflected back from the front diffuser.



Putting the Omni-Bounce back in place with the front diffuser creates double diffusion where the light emitted from the flash is no longer a beam and spread to create internal reflection.

Do remember that anything you place in front of any light source, flash or continuous, unless it is totally clear and without colour will reduce the light output; here I had to adjust the flash power incrementally to over two stops from the initial exposure to maintain a constant aperture. I was using the Manual setting on my flash for this exercise, but if you're working TTL the camera and flash will look after the exposure for you.


With a few exceptions, the interior of soft boxes is a bright specular neutral silver as this is the most efficient reflector. If you line a soft box with a less reflective white neutral material such as Rosco﹟3830 Spun Silver (which incidentally is double sided benefiting from textured silver and textured white sides) this has the effect of diffusing the internally reflected light creating an even softer light with shadows exhibiting broad edge gradation and less density.


If you are lucky enough to own or have access to portable battery flash such as Elinchrom Ranger Quadras the light quality will differ as the flash tube is not enclosed as with a Speedlite, but totally open  emitting light in all planes.


If you add a deflector inside the soft box you have a very usable beauty dish giving an edgy diffused light which is very much in fashion at present. Adjusting the position of the deflector will create different shadow effects - remember that light illuminates and shadows define.


Broad soft light created with a combination of internal Rosco﹟3830 Spun Silver (white side), a silver deflector and white front diffuser. Elinchrom produce a set of deflectors which include a gold, white and translucent offering differing looks. Even the textile on the front of the soft box will alter the look of the image. 


If you are able, it's sometimes best to get a feel for lighting in controlled and constant environment away from models, this will then give you greater confidence in the studio with models. Fred has numerous relations all who are available for reasonable prices from shop fitting suppliers on and off line.

In his basic form Fred is unpainted white polystyrene which I painted with water-based emulsion testers from the local hardware/DIY store.


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