Are there blue harebells?

[Inkanyezi]

I know that the harebell is also called bluebell in Scotland, but bluebell is a variety of different species in various parts of the world, so I stick to harebell for this variety of witch thimble. Last year, on another photo forum, a poster complained that he could not get the correct blue colour on his harebells, and he presented an image that was wildly out of tune and overexposed as well. The conversion and handling of tonality was probably what wreaked most havoc, but the main problem certainly is that the harebells aren't actually blue.

Now our medium, the digital camera, has its own way of handling violet. As there is no violet in the tristimuli RGB of our images, the software presents it as purple on our screens, by adding a bit of red to the blue. This is conceived in the camera, by the CFA red filters transmitting quite a bit of violet radiation. So the red filter in the CFA is not only red, but also violet. I wonder how the Foveon might handle violet? If it is filtered out in the first two layers, very little will reach the bottom layer. Of course the green channel can help identify violet to the conversion algorithm, but then a rather strange unlinear algorithm would provide red for the computer screen. This certainly appears more simple with a tristimuli-imitating CFA.

So, I thought of it as a bit of a challenge. Who will find really blue harebells (or bluebells)?

At least the bottle I put them in is blue.

[Shadowman]

Nice capture.

[Geoff F]

Many flowers considerably change their colour depending on the light.

I have picked blooms and brought them inside to compare directly against my computer image; but as soon as they come indoors their colour changes.

The best option for me is to avoid direct sunlight and do a custom white balance with a proper balance card. Shooting Raw does make WB changes a lot easier but even then I find the custom balance before shooting gets your starting point fairly close to correct.

[Inkanyezi]

With digital capture we usually don't have the problem with UV that film had. When bluebells are taken indoors, as in my image, taken in window light behind glass panes, there is hardly any UV radiation getting in, but also the filter in the camera blocks most UV radiation.

But in cameras with colour filter array, CFA, the red filters also pass violet, in order to present it to the tri-colour screens as tri-stimuli. In essence, the presentation on screen does the same as similar filtering in the eye, as our red receptors also react to violet. Most blue flowers have a rather large proportion of violet, but there are also flowers that are more saturated blue.

[IzzieK]

This conversation is too techie for me, Urban...so allow me to comment on your image. I have studying light shaping lately on one of my online courses but I have yet to go to the next course which is table top photography. Too many distractions lately. Anyway, I would like to ask if you have that light from the window to work with because the shape of the bottle turns out very good here. In the course that I am taking, because I lack the equipment to hold scrims and reflectors, I do not believe I can get that bottle shape as well as you did here. Pretty remarkable. (Reflector arm stand and some stuffs on order.) Tabletop photography is good when it is raining outside and during winters. Very nice shot btw...I like the lighting as I have already said.

[Inkanyezi]

Thanks Izzie. To tell the truth, I didn't particularly bother about the shape of the bottle, but was somewhat worried that it would not stand out, as the black background subdues any transmission through the glass and water. I wanted to have a light on the flowers that models their shape, and I chose to backlight a bit, in order to get the background dark and have the flowers stand out, just hoping that the blue of the bottle would come through. It is really a bit posthaste, using only the window for lighting without any reflectors or anything fancy. I just draped one of the chairs with black cloth and turned it to get a partially backlighted scene. To help contrast, I shaded the lens with my hand, so it would not receive direct light from the window. When backlighting with a black background, for low key, there is a substantial risk of fogging from light hitting the lens directly.

It was taken at about twenty to nine in the evening, so the light was fading rapidly and also changing colour. I measured white balance, but it became a bit off anyway for the time between measurement and exposure. I used the jpeg out of camera, but tweaked it a little. I also have the RAW in case I would want to do a more thorough job on WB and contrast. But I made this image as part of a discussion about the colour of those flowers. So far, I have not seen any harebells that are pure blue. The French beer bottle however is blue, and I hoped it would show sufficiently to see how off the flowers are.

Violet is a colour that does not exist in our display media, considering the very short wavelengths, although it is presented as a purple, from mixing red with blue. Therefore, the Colour Filter Array, Bayer filter, also has violet transmission in its red filters. Not actually RGB in that end, but RV-G-B, while the display media are RGB. For our eyes it's the same thing, as our red-sensitive cones also respond to violet. So even though our displays cannot emit violet, they can supply the same sensation that violet does, by tickling our colour sensitive cones in the same way.

[tao2]

Aye,

Fading tae blue...







Not violet...mebbe some lilac...





Not purple...





Blue...

[IzzieK]

Big difference between the bottle and the flowers which you had shown here. I understand your explanation and wanted to try to capture that colour in a flower but I am busy traveling at the moment. I was thinking of violet flower and I googled it, it is violet (purple) then I googled bluebells and there are some that are blue. Googled blue flowers and there is even a blue lotus and blue orchid...This is becoming interesting to me. There are some blue flowers (probably food coloring) from the supermarket and will try to replicate its colour when I come back home. Thanks.