Jump to content
UltravioletPhotography

Hello from France


IanR

Recommended Posts

I joined your group today as a complete novice in the field of UV photography and without any appropriate photographic equipment!

 

My reason for joining is that UV photography could prove useful in a project I'm working on in my retirement; a taxonomic revision of the African butterfly species in the genus Neptis (Nymphalidae) There are over 80 described species from Africa and DNA barcoding has shown up at least 20 additional species yet to be described. They are medium sized butterflies (4 to 5 cm wingspan) and the majority have white markings on a dark brown to black background. The barcode work reveals that there are several groups species that are almost impossible to distinguish in the adults, whilst the individual species are very well separated. It's just possible that the Neptis have distinctive markings in UV colours and if so this would add a powerful identification method to sort out these difficult groups.

 

It could of course be that the Neptis don't have any distinctive UV markings or that they are very variable from specimen to specimen and so don't help with identification. If this turns out to be the case, I can at least report the negative result.

 

As a start off, I'm asking if any member could help me out by photographing a small batch of specimens, 6 perhaps, so that I can see whether this line of enquiry is worth pursuing. This would be a great help and would enable me to direct my limited funds to the most productive work.

 

I've attached a photograph is some Neptis specimens as an example of a near cryptic group. All are undescribed and separate species, except the one from Cameroon, which may be a subspecies of the top one from the DRC.

 

IanR

post-124-0-44302200-1470404760.jpg

Link to comment
Hi Ian, this seems a very interesting project and something that a lot of people are experimenting with more often now that the technology is becoming available. I'd love to help you out with some images, but I'm in the UK so it would depend if you can safely send samples, I've no idea how valuable they are or how easy it is to transport them. I certainly have enough equipment to explore the UV-A band around 360-390nm, although if you expect the markings to be in a lower band then I expect other members here have some useful (albeit more expensive) equipment
Link to comment

First, welcome to our small UV-based corner of the cyberspace. Members cover a wide range of expertise, though, and are all helpful.

 

As to the question of making UV images, can these specimens be sent by mail or must they be examined in situ?

Link to comment

Hi Jonny and nfoto,

 

Thanks for replying so quickly. The main collection I'm working on is at the African Butterfly Research Institute (ABRI) in Nairobi where they have a mind numbing 9000 Neptis specimens, probably more by now. I'm going back there for 6 weeks in October. In the meantime, however, I have a smaller number of specimens mostly sent to me by a collector in Malawi. I have finished setting them out and taking samples for barcoding. I can select half a dozen for a UV photography test, detach a forewing and hindwing and post them quite safely with the wings in glassine envelopes. I just need to take good visible light photos of each specimen first and to that end am waiting for a batch of high CRI LED bulbs to be delivered; the bulbs I'm using currently have a pronounced green cast that has to be removed in Photoshop. So later next week I could post off a set of samples.

 

Should I send them to you Jonny in the UK seeing as you were first to reply to my post? I've read that the 365 nm region is visible to insects and so the range you can process should be fine.

 

Many thanks to you both for your interest and offers of help.

Link to comment

Ian,

It sounds interesting. I did some UV work with riparian insects.

Will you be working with solar UV?

If Jonny is unable to help you, add me to your list. The UV markings of male butterflies are fascinating. However, in some species the UV range for peak reflection is very low --

http://uvroptics.com/images/Butterflies_Page_4.jpg

from http://www.bioone.org/doi/pdf/10.2108/zsj.19.175

 

I think I can manage 320nm with a special filter.

 

Regards,

Reed

Link to comment

Some of those bands do look exceptionally low Reed, I certainly can't reach 320nm, that is pushing the limits of a DSLR I imagine, even with a quartz lens and a special filter. Looking at that report however it looks like there should be a lot of UV reflectance, so we should still record a pattern in the longer wavelengths.

 

Ian I am willing to take a look for you, but you may need to seek out more specialised equipment depending on where these markings reside, I'm assuming that since this is new research, until you start investigating nobody will know. Recording down at 320nm will be tough!

Link to comment

Hello, Ian. And welcome to UVP!!

 

Your butterfly project is quite interesting. I have an initial question: does the UV reflectivity or absorption pattern change when the butterfly is no longer living? I suppose the underlying pigments would still be present in the wing. But would they dry out or anything?

 

The data about the UV reflectivity in the 318, 321, 348 and 341 nm regions indicates that it would be important to use a UV-dedicated lens such as the Coastal Optics 60/4.0 or the UV-Nikkor 105/4.5 or any industrial UV lens reaching that range. And you would also need to use a UV-pass filter in the appropriate range. Most of the typical wideband UV-pass filters (such as the BaaderU) won't work for the 318 or 321 nm region. So special filters might need to be purchased. This could be rather expensive.

 

A converted camera should be able to record the 318 - 341 nm region with proper filtration, lens and illumination. It might be tougher on the 318 nm end however. I just don't know from personal experience.

 

The UV illumination is also important. There are not any specific narrowband UV-LEDs available in listed UV regions. So the illumination would probably need to be accomplished with a Xenon lamp or Xenon flash. If it was a very still day, the photographs might be able to be made outdoors in the sunlight if the wings were carefully pinned.

 

The 348 and 341 nm regions would be most easily reached and should give no trouble (again, with with proper filtration, lens and illumination). So butterflies with those reflectivity patterns are probably the best ones with which to start your experiment.

 

Any photographer attempting photography of these butterfly wings also needs to remember that the effects of hot lamps or flashes might be destructive to the artifact. It is possible that a protective glass cover could be useful if it did not cause reflectivity problems? Bjørn would know the answer to this as he has photographed such things as pieces of the Dead Sea Scrolls and would be aware of protective measures needed to insure that there is no damage from heat, lamps, etc.

 

Please let us know if we can be of further assistance.

 

(I have just got in a narrowband 340 nm UV-pass filter with high transmission and an approximate 10nm bandwidth. This might be useful for the 341 nm case.)

Link to comment
Andy Perrin
does the UV reflectivity or absorption pattern change when the butterfly is no longer living?

 

Andrea, while I don't know the answer to that question for sure, my understanding is that butterfly patterns in VISIBLE light come from interference phenomena, not from pigments. Dying might cause the tissue to shrink from drying out, which could shift the pattern a bit. But I would not think it would change things very much, because the butterfly colors in visible light don't change a whole lot when they die as far as I'm aware?

Link to comment

Hard to say, really. Some specimens I've seen do look faded. It likely has a lot do with methods of preservation and protection.

 

Butterflies have both pigments and structural iridescence, I think. This is a go-look-up topic. :D :D :D Later, when I have a mo'.

Link to comment

An interesting article. Thanks, Reed, for the link.

 

Main point of the article: do not attempt to quantify UV colour signals from a subject without taking into full consideration the interplay of the spectral properties of all equipment in use. Something, BTW, we have also repeatedly stressed here on UVP. :D What we see in our UV photographs may not show the whole UV story.

 

One example used in the article: The Yellow Sulphur butterfly reflects 60% UV at 340nm and 20% UV between 370-380 nm, as measured spectroscopically. When photographed under artificial UV light (either a fluorescent UV tube or ring) with a non-UV-dedicated lens (here the 105/2.8 AF Micro-Nikkor), then the entire reflection at 340nm would be missed in the photograph because the lens, UV-pass filter and lighting combine to give a photographed range between 360-390 nm with a strong peak around 375nm.

Link to comment

Please sign in to comment

You will be able to leave a comment after signing in



Sign In Now
×
×
  • Create New...