U330 + BG40

[Jim Lloyd]

First attempt with new U330 filter 1.5mm + BG40 2 mm as attempt at a "bird vision" stack

 

D3200 converted, iso 1600, 1/20 s, f/5,6, handheld! Photax 35mm f/3.5 preset. Outdoors early afternoon, light cloud cover. WB using viewNX2 using point reference on gravel in background. Some boost to saturation and contrast.

 

NEF file is here

 

On very quick tests WB is more difficult than for UV. Seems sensitive to amount of UV light and lens used. I guess because ratio of UV to visible is important. If just doing UV than one can compensate with longer exposure, but for stack like this ratio of UV to visible will be important.

 

[Andrea B.]

Review for me please what primary visual receptors a bird has? Are they UV, blue and green? Thanks. I have a few generalized remarks about representing vision for UV+blue+green if you confirm that.

 

As a general remark, we note that this is false color, so you are free to use whatever color palette you wish. But I know that almost everyone wants to white-balance this type of false color -- and for good reasons.

 

White balancing and color profiling combined generally yield the color palette you show here. So you are on the right track. However, for the work which you want to do (I think?), the thing to aim for is some standardization of your color palette so that your examples may be safely compared in relation to one another. So you will want to obtain some kind of white standard to use which holds its reflectivity in both UV and Visible. The main thing used by most UVP members is PTFE, teflon. There is some info in the white balance sticky about PTFE.

 

Once you have the PTFE, you make an initial test shot of the subject and the PTFE at the beginning of every shoot. Then in the converter, you use the white balance tool on the PTFE and save the resulting WB as a preset for use in the photos which do not contain the PTFE.

 

Sticky :: White Balance in UV/IR Photography

[Jim Lloyd]

Bear in mind I am only at the very start of my studies in this area, but I understand that birds have four colour receptors - in very simple terms UV,R,G,B. Not all birds are the same. The RGB receptors are spread more evenly over the visible spectrum that in the human (of course RGB is not really correct for humans).

 

In terms of what I am trying to do - as my project is an art practice based one the approach is very much about learning through doing. A "leap before you look" approach. In art I find one often doesn't know what you are trying to do until after you have done it - maybe quite some time later. Of course this has to be balanced with some knowledge and direction. In theory this might lead to more interesting paces than a logical series of steps from the known ??

 

Anyway the idea here was to have a stack that gave UV+RGB - I am aware that it might not be the ideal or first choice, but I wanted to try something out at relatively low cost, utilizing the BG40 2 mm I already have. There has been discussion of this topic here

[Andrea B.]

oh la! This is about the 14th time today I've forgotten about one of the 5000+ posts I've written......sorry 'bout that.

 

OK, 4 receptors. That is very difficult for me to wrap my mind around. How does one come up with a human trichromatic model of a bird's quatro-chromatic vision? Good question. I'd first read a bit more about how this works in the bird brain. As an example of something to investigate: Does the bird perceive the UV separately from the R, G or B? Or are the signals from the 4 receptors combined in some way? If it is the first, then modeling their vision by means of photographs might be easier than if it is the 2nd.

 

Here is an analogy: When we listen to a chamber music group consisting, say, of a piano, a violin and a cello then we can hear all three instruments simultaneously as distinct instruments. But when we view a particular color which is some mix of RGB wavelengths, we see it as a single color and we are not aware of viewing three distinct colours simultaneously. Do you see the difference in these two types of perception? So try to discover how the bird vision works.

[Jim Lloyd]

As far as I know birds perceive a single colour from the 4 receptors - I think the Human and avian visual system has a lot of similarities due to a common evolutionary ancestor. In fact I understand that we might have lost a receptor rather than birds gaining one ...

[Cadmium]

oh la! This is about the 14th time today I've forgotten about one of the 5000+ posts I've written......sorry 'bout that.

 

OK, 4 receptors. That is very difficult for me to wrap my mind around. How does one come up with a human trichromatic model of a bird's quatro-chromatic vision? Good question. I'd first read a bit more about how this works in the bird brain. As an example of something to investigate: Does the bird perceive the UV separately from the R, G or B? Or are the signals from the 4 receptors combined in some way? If it is the first, then modeling their vision by means of photographs might be easier than if it is the 2nd.

 

Here is an analogy: When we listen to a chamber music group consisting, say, of a piano, a violin and a cello then we can hear all three instruments simultaneously as distinct instruments. But when we view a particular color which is some mix of RGB wavelengths, we see it as a single color and we are not aware of viewing three distinct colours simultaneously. Do you see the difference in these two types of perception? So try to discover how the bird vision works.

 

Sound is different, it has a wave shape, sign, saw-tooth, triangle, square, and all sorts of mixtures of the like. That is one of the ways we can distinguish one kind of sound from another, voice, instrument...

With light, color (I learned to spell in the USA, so that's how I spell it) is is the frequency, and it has only one wave form, it mixes together, and your brain sees the mixture as a unique color, and your brain may know that the color is a mix of other colors.

With sound, even if two or more instruments (or voices, say) are making the exact same notes (frequencies) at the same, we may still be able to distinguish which instruments are mixed together by the various wave forms.

With sound, even if two or more instruments play different notes at the same time, AKA 'a chord', the individual frequencies are still distinguishable from each other in our brain without learning what notes make up that chord.

 

I once met a bird that went to Harvard, got a PhD in Humanology, and told me that basically if you boil it all down, "those humans think too much sometimes".

[Andy Perrin]

Sound is different, it has a wave shape, sign, saw-tooth, triangle, square, and all sorts of mixtures of the like. That is one of the ways we can distinguish one kind of sound from another, voice, instrument...

With light, color (I learned to spell in the USA, so that's how I spell it) is is the frequency, and it has only one wave form

This is not true. The case of sound and light are nearly the same in this respect, in fact. The mathematical version is that ANY repeating signal can be written as a Fourier series (sum of sine/cosine waves). That includes triangle waves, square waves, and so on!

 

Example from http://mathworld.wol...rierSeries.html

 

The only thing that makes light different as far as constructing mixtures is concerned is that the wavelengths are so short that only special equipment would be able to pick it apart into individual sine waves. Such an instrument is called a spectrometer.

 

Light and sound are different, though, in one respect. Since light is made of electromagnetic waves which have an orientation, light has a polarization.

[Cadmium]

My point is, if you have a specific wavelength and band of light, and you mix it with another of the same wavelength and band, you don't know any difference, they are the same.

If you mix one instrument sound with another, same note/frequency/wavelength, you hear two types of sounds, even though they are the same wavelength, if you try, you will say,

that is a flute and a piano playing the same note.

Furthermore, listening to a chord of two or more notes, you can separate the specific individual notes in your head, if you try.

[Andy Perrin]

I understood your point, but you can do that with light if you want also. It's not a distinction between the two. The only reason you can't do it in your head with light is that we don't have senses that can sample the light fast enough, so you only get the average value when you see it with your eye. Sound waves vibrate at most 20,000 Hz, whereas light in the vis range is around 500 trillion Hz. And you can certainly detect variations in the amplitude that are at human times scales, like a blinking traffic light.

 

There is even a device called a duplexer that does it with radio waves (a form of light).

https://en.wikipedia.org/wiki/Duplexer

[Cadmium]

Jim, Nice shot. Usually with my U-330 stack the green in the center looks more pronounced. Your background colors look right for that stack to me though.

I tried your NEF, and no mater what I did it was about the same.

Oh, wait, you are stacking with BG40 instead of S8612... that might be the difference, I don't know.

 

Here is the comparison, so maybe the red bump is thinning down the green center some in this instance, perhaps?

[Jim Lloyd]

Hi Steve, thanks for that. Helpful to know you didn't get any different white balance with the NEF. Did some more playing around today. I like the fact that I can get some idea of the final image in Liveview by adjusting the in camera white balance. Still very red/magenta but it gives an idea. Plus I can work hand held.

 

I found I could get some variation in the amount of green in the dandelion depending on the lighting (i.e full sun or cloudy) and the degree of exposure. But essentially they were all similar to what I have already shown. I think you are right the difference between what you have shown before and this stack is that red bump. Which was intentional as I was thinking about bird vision. In very crude terms birds are a bit like bees in their vision, but have the additional sensitivity to red.

 

Very interesting discussion about waves, but I need to think that through a bit more before I reply.

 

I was thinking though that its not strictly true that we don't have some awareness (or can develop it) of the individual "colour channels" in our vision. A painter can learn to mix paints from 3 primary colours and sense whether the colour he has needs a bit more red or yelow for example. I know we just percive a single colour, but I would argue we can have some sense of its components. So maybe some animals can have something of a UV sense. I really need to read up on this rather than speculating.

 

Anyway had some fun with the filters today (same settings as above)

 

 

 

 

[Cadmium]

Oh wow, those are gorgeous! I never tried a poppy with UV+Blue+Green stack.

Yep, you can work hand held with such stacks, in fact, shoot two shots, one UV only, the other UG5/U330 stack, convert both the UV-only and UV+Blue+Green stacks to monochrome, how do they compare?

[Andrea B.]

That analogy I made, if pushed too hard, will readily fall off the cliff !! :D :D :D :D

 

Nice work, Jim.

[Cadmium]

...but Andrea, did I mention that the bird owned a spectrometer? :D