Thursday, 13 August 2015

Lightbox images

Lightboxes are used to provide strong backlights. I've been experimenting with one such device to illuminate flowers and include the translucency of petals and leaves in images.

This poppy came from my garden. I had been unsuccessful in trying to capture an image of a poppy with backlight and showing light through the petals. I brought the flower into the house where I could use a lightbox as a source of backlight. The lightbox was placed on the floor and the poppy was placed on the lightbox. The camera was tripod mounted with a cable release attached. Aperture was set to f/18 to ensure sharp image. A few trial shots showed that a short exposure in the order of 1/15s resulted in an image that was close to a silhouette of the flower with little colour visible, and a long exposure of 15s was sufficient to produce an image that was almost entirely burnt out.

Based on this, I decided that seven shots taken at 1-stop intervals would adequately cover the range of useful exposures - that fastest at 1/8s and longest at 8s. These seven shots were followed by one further shot with the lightbox switched off and using natural light through a window to obtain a normally exposed image.

The images were opened in Photoshop and stacked as layers (The relevant commands to do this are: File > Scripts > Load Files into Stack... Add Open Files, and tick the checkbox Attempt to Automatically Alight Source Images.) The darkest image, 1/8s exposure, was placed as the bottom layer and the extra shot with the lightbox switched off was placed at the top. It's handy to know the command to reverse the order of layers here: Layer > Arrange > Reverse.

Starting with the bottom darkest layer, each subsequent layer is processed in turn: a black layer mask is added to the next layer and a white brush is used manually to selectively paint in parts of the layer.

Orange poppy

Deconstructed orange poppy