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UltravioletPhotography

Local Park in UV Light


colinbm

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Thanks to Bjorn for the opportunity to try out the Andrea-U filter (about 320-400nm), with the Tiffen Hot Mirror to cut the small IR leak. I tried it out at my local park on the Sigma DP1 compact with the hot mirror removed.

I liked the results, (no internal reflections, from the coatings, that other filters have) even though the camera can only capture down to about 380nm.

Both colour & mono converted.

 

post-31-0-99748300-1388142662.jpg

 

post-31-0-40481300-1388142699.jpg

 

 

Cheers

Col

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An interesting image, Col. I'm wondering how much visible violet/blue component there is ? A tiny bit, perhaps.

Once the saturation is reduced, the details are massive from the Foveon sensor !!!

Well, that is known to be one of its strengths. :lol:

And I saw it myself when experimenting with the uploads you so kindly supplied.

 

What was the focal length and speed for this foto?

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Thanks Andrea

I would say the image is of about 380-400nm.

The first UV-blue image was much better before it was posted here, like the B&W one. It is OK on my Flickr page... Andrea-U UV

The Sigma DP1 Focal length is 16.6mm, 35mm equiv is 27mm.

This image was shot at ISO 100, shutter speed is 0.6 sec, aperture f10.

 

The exif is.....

 

File Name: SDIM0465 Andrea-UV 320-400nm shade.jpg

File Type: JPEG

Image Dimensions: 4.6 MP (2640 x 1760)

File Size: 6.82 MB

Location: C:UsersColinbmPicturesSIGMA DP1 Full SpectrumDP1 Andrea-UV 320-400nmSDIM0465 Andrea-UV 320-400nm shade.jpg

Capture Date: 26/12/2013 1:33:10 PM

Exposure Mode: M - Manual Exposure

Exposure Compensation: 0

ISO Setting: 100

White Balance Setting: Shade

Color Mode: Normal

Flash: Off

Shutter Speed: 0.6s

Aperture Value: F10.0

Metering Mode: Spot Metering

Focus Setting: AF-S - Single Auto Mode

Focal Length: 16.6 mm

Resolution: HI

Drive Mode: Single Frame Shooting

Camera: SIGMA DP1 1004294

Firmware Version: 1.00

Image Unique ID 30313030343239341630BC5264323237

Modified: 26/12/2013 9:37:39 PM SIGMA Photo Pro 5.4.1.0000

Exposure: -1.6

Contrast: +0.7

Shadow: -1.1

Highlight: -0.5

Saturation: +0.0

Sharpness: +0.0

X3 Fill Light: +1.3

Color Adjustment: 0

 

 

Color Space: sRGB

JPEG Quality: 12

Adjustment Mode: Custom: Current Unsaved Setting

 

You can have this Sigma .x3f file if you like ?

Cheers

Col

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  • 10 months later...
Whatever was done to the color version of the image just murdered the spatial resolution. Was the b&w knockdown from one channel, or all three? Could the blurring be CA?
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Hi Clarke

I am still getting used to the Sigma Foveon cameras for UV c365nm photography.

The Sigma Foveon cameras give an essential blue channel only response to UV. Even though the LCD shows a nice .jpg of the shot, the RAW image shows a lot of magenta, which I try very hard to avoid, as I consider it a result of over-exposure of the highlights & is clipped.

So when I process the RAW image & am trying to eliminate the magenta, there is usually no data in the green channel or red channel.

Am I doing something wrong ? Klaus, tells me on Flickr that the Sigma's are useless for UV, but I don't mind the mono blue or B&W mono.

I have experimented with different filters to get some UV, blue, green & yellow, (365 - 500nm). I would like to find a 52mm NGB filter.

Cheers

Col

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Col, how do I find your Flickr page?

 

I don't know the size of the original uploaded blue image, but it is entirely possible it got resized by the Forum software if it was larger than 1000 pixels max (or maybe larger 1200 pixels max). So that could account for the lack of sharpness. Just guessing, not entirely sure. So I thought I would look on your Flickr page (if I don't get swamped by ads!!).

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Thanks, Col.

The sizes available for the Blue Park foto from your Flickr site are 2640x1760 (original), 2048x1365 (large) and 640x427 (medium). I'm thinking that you probably uploaded either the Flickr original or large size here and our forum software compressed it to a maximum dimension of 1000 pixels, our upload maximum at that time. So it does not display well here either in the 800 pixel post size of the 1000 pixel click up size because going down from 2640 pixels to 1000 pixels is just too much for the forum software.

 

It is best to resize your photo prior to uploading here to a maximum between 1000 -1200 using some good software app which can resize an image without losing so much resolution. Then when your photo is clicked up here, it will show a good res.

Alternately resize the photo prior to upload here to the maximum post size of 800 pixels. When clicked up the size won't change, but you will get the nice display background.

Or, one last option, resize the photo prior to its Flickr upload. (whew!!!)

 

Hope this helps improve the display of Blue Park.

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My Sigma experience is limited to the SD14; I cannot speak for how other models behave. Everyone has a different definition of "useless." If you are after multiple color channels each of which encodes different UV spectral information, then any laminar sensing medium is "useless;" you need a reseau of some sort to do that well. The Foveon's UV sensitivity may also fall short of that of the performance of the Nikon D70, which seems to be the gold standard in this community, and I do not know whether it can respond to wavelengths as short. I have respect for Dr. Schmitt's judgment, but it is my impression that he took only a few test shots with the SD14 before dismissing it as not worth further investigation; and if you have a closet full of CCD Nikons, I can understand this. I do not have any such gear myself, so my view is a bit different (I did not even have a converted DSLR until a few months ago.)

 

Also, Foveon cameras use more complicated firmware to extract the RGB image than those cameras with Bayer sensors, because the direct sensor output is not RGB as such. When operated far outside its design envelope conditions this firmware can do bizarre things to an image. I can mount a 525LP filter on the camera, and the green channel disappears, even though the filter does not block green light! With the Baader filter, I have seen good detail in the JPEG thumbnail...only to find that the X3F primary file is badly degraded or blank! There are similar antics in the IR, which make R72-style color IR with these cameras impossible. Sometimes I just shoot at the best resolution I can, and extract the JPEG thumbnail in those cases, chucking the X3F out. An NGB filter will undoubtedly give you a result--but it will likely not be what you expected.

 

As a B&W instrument, I find the Sigma capable enough for a 4.6 megasensel camera; but in those few cases where I left the color in on a UV photo, I admit I may have been recording visible or IR leakage.

 

The SD14 is my go-to travel camera because of its manually removable hot mirror, something I have seen on no other camera; it can wear many hats as needed, and its visible color images are of decent quality. As for the UV images I have taken with it, let the viewer decide.

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The Sigma that I use is the SD10.

 

If I remove the HM filter (takes 1 min) then I hardly get any response to the green channel. But sensitivity increases by several f-steps. In other words if I take photos without HM the sensitivity from uv to ir differs by 6 f-steps. It seems the maximum response is ir, and minimum at green. A green filter Hoya G(X1) improved that but cuts uv at about 375nm too. Perhaps it is possible to make good uv and full spectrum shots but I was not successful at all.

 

My SD10 has a horrible power consumption far beyond everything. A new set of batteries works for 7 pictures and after a while i can wind 3 others out of the batteries. I built a converter to use the battery of my cordless drill. :-(

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Nikon D70, which seems to be the gold standard in this community

Just for the record, not really. :) We don't really have a 'gold standard'. Everyone shoots something different. I think the newer mirrorless cams - either Panasonic or Sony NEX/alpha may have the most users amongst the UV shooters I know about.

 

This brings to mind the following observation - purely my own, but it seems reasonable --> I'm not sure there is one single camera model which could do everything in the best manner possible in the UV photography world. Certainly this seems to be true in the Visible photography world. For one example: The Panasonic G line are simply the superior video cameras currently, by all accounts. So if you want or need UV video, then you go there.

 

My general observation is this --> the better the sensor, then the better the photograph. This is true in any of the UV/Vis/IR wavelengths. But, like always, this observation must be weighed against the photographer's actual needs and intended uses. When we are learning and experimenting and posting images to be shared online, we certainly do not need a converted 36MP Nikon D810 or any similar cam from any other brand. If we are seriously pursuing UV photography, then the lens really becomes an equally important factor - maybe the most important factor.

 

Well, I could rattle on like that, but I'm sure you all understand very well the pros & cons of the various choices. Above all, use what ya got and learn to get the best from it.

 

It has been very interesting to learn more about the Sigma Foveons.

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With the Baader filter, I have seen good detail in the JPEG thumbnail...only to find that the X3F primary file is badly degraded or blank!

This is very interesting. I'm not sure I can think why the raw file would lack the data that the jpg shows?? I wonder if it has something to do with the particular converter used? Or does the Sig Fov firmware completely "divorce" the two file types, which would be way weird.

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What we are missing here is a good UV shoot-out between a Sigma Foveon camera and some CMOS camera so we can compare what is or is not captured when the same lens and UV-pass filter is used on the same subjects. I hope we get to see that someday. "-)
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Andrea I do not think the different Sigma cams behave in full spectrum and uv as similar as different CMOS cams.

 

When I compare the results from my SD10 and Colins with DP2 or SD14 then they are completely different. For example (my) SD10 doesn't even execute a white balance without filter (HM or green).

 

The influence of the HM is different and the result in XF3 files is different to. One has no access to the foevon sensor, only to the xf3 files... So I do not think it makes sense to talk about "the foevon sensor".

 

I failed in converting my EOS/Rebel 300D (finally) so I can't compare for the moment.

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Thanks everyone

Sorry to hear your Canon conversion didn't work out Stefan....any particular problem ?

 

With the Sigma Foveon cameras, I have always wondered why the embeded .jpg was sometimes different to the RAW & often I couldn't get close enough to it in the conversion, it is pretty annoying when you shoot a number of shots to get a nice result in the LCD, but to only get a glance of it while the RAW converter opens. I guess I should go back over some of my snaps & just open the embedded .jpg & learn to work with that. I am not good at post processing, I'll have to put more effort into it.

 

Clarke, I think all the Sigma digital camera models work differently when used out of the visible spectrum, even differences between batches in the same model.

I am wanting to try the SD9 one day for UV, after the cover glass on the sensor (it is also an IR cut filter, as well as the dust protector glass) has been replaced with quartz, it also has no microlenses that may attenuate the UV some. The only problem I see that may affect the outcome is the thin layer of silicon, 0.02 um, above the top blue receptor, just how much of the UV it attenuates ?

 

Cheers

Col

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Trying to convert this old cam was not a good idea. The plastic levers of two connectors broke like glass under my coarse fingers. One of them was that of the sensor cable.
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When I open my UV or IR pictures (shot with pre-set in-camera WB) in Capture One I also do not get the same results as in-camera JPGs. Capture One has its own camera profiles so it is not surprising that it tries to adjust the colours based on its own independent settings thus "screwing up" WB. But tha can be fixed. On the othe rhand, Sony dedicated IDC software (I use Sony cameras) shows RAW files exactly the same as in-camera JPGs. It is hard to understand why Sigma's software can not render it properly.

 

Stefan, what type of connectors did you break? It might be possible to fix them.

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For more entertainment, here is one where I left the color in:

 

"The Gas Station Blues." SD14, Asahi 35mm lens, Baader U2 filter, Earth City, Missouri.

 

post-66-0-17549300-1416154126.jpg

 

 

I am not sure whether this was worked up from the primary or the jpeg. I detinted most of the foreground and was left with this outrageous sky color--like something out of one of John Meaney's necropunk novels. I don't know how it originated, really. Note also the fine pale bordering lines between the sky and the foreground and the blacked-out traffic lights in the distance. I can explain the latter, but not the former.

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Not the connector itself but the small levers that fix the cables...

 

Hi Stefan

You may find an spare lever in a discarded DVD player or other computer component that has ZIF cables & the same connector & rescue a lever for the Canon.

Col

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