How to set up a live UV cam? [Progress was made!]

[Andy Perrin]

Andrea, is there any use for the Color Checker Passport thingy in UV? I have one and I've used it to correct my VISIBLE images, but occasionally I see people on here photograph the Color Checker and I've never understood why. Surely you can't use it to correct the false colors? It has no yellows.

[Bill De Jager]

Thanks, Andrea! I usually use Adobe Camera Raw but I also used PhotoNinja for a while years ago. I still have a rather old version on my offline desktop, and I'm thinking of getting a new license and installing it on my current workhorse laptop.

 

Anyway, I'm confused. You mean take the photo in monochrome and then use the raw processor to turn it back into color? I've never been clear on what the monochrome setting does for pixel-level processing. Of course pixels are just allocated to different luminance levels with no color, but I don't know if raw processors try to average out these luminance levels with adjacent pixels to avoid checkerboarding caused by the Bayer matrix. Are you saying that it's possible to take a "monochrome" raw image and process it as a color image? It makes sense that you could do that with the raw data, but I want to make sure I'm not getting this wrong.

[Andy Perrin]

BIll, the monochrome setting only affects what you see in the viewfinder and the JPG. The RAW is unaffected by it, so there's no "turning it back into color," it's just processing the colors that are still present. ACR does not work for UV white balancing (RAW or no-RAW), so if you are getting odd results, that's probably one reason.

 

Andrea's saying to take advantage of that to use the monochrome mode to prevent overexposures.

[Andrea B.]

Unfortunately Adobe Camera Raw is not the best for converting reflected Ultraviolet raw files. Strange, but true. ACR simply cannot obtain a "proper" UV false colour white balance. It is somewhat like a Nikon in this respect. Neither seem to have the temperature range required for successful UV white balance.

 

There are several other choices besides Photo Ninja. Even some free ones. I happen to like Photo Ninja, but it is more or less "historical accident" that I came to be using it. I stayed with it because of its amazing color profile capability.

 

I want to make sure I'm not getting this wrong.

You are not getting it wrong. But I'll run thru this in case any newbies are reading.

 

If you are shooting Nikon raw files, then any Nikon Picture Control or any Nikon WB setting affects *only* the stored Jpg made from the raw file. It is that JPG which is what you see on the LCD monitor.

 

If you open the raw file in a Nikon converter (View NX or Capture NX), then you will see the raw file with the Pic Control and WB settings applied, but you are free to change both without affecting the underlying raw file. (Altered settings are saved in a section of the file not affecting the raw data.)

 

If you open the raw file in a non-Nikon converter, then you may or may not see the Pic Control or WB settings applied. Photo Ninja, for example, does not or cannot "read" the Nikon Monochrome setting, so you would see a UV raw file initially in Photo Ninja in all its gory red/magenta color until you applied a white balance setting. (White-click on the magenta areas for a quick WB fix.)

 

So..... shooting reflected UV under the Nikon Monochrome Pic Control is done simply because it produces a B&W JPG on the LCD which better enables you to determine what exposure you are getting because the JPG is not overwhelmed with gobs of red much of which hits the right hand wall of the JPG histogram. That red obscures detail and mades it difficult to determine whether you have blocked shadows. Even though the brightness histogram for the Mono Pic Control is for the JPG, it offers a very good estimate of where the raw brightness will be found.

 

I've never determined whether the Nikon Mono setting is a simple desaturation, a greyscale or what. Probably some combo of those two and other tweaks. It doesn't matter what the Mono does when using it in reflected UV work because we will "un-apply" it in the Nikon converter or not even see it in other converters. BTW, I use the Mono setting with contrast = 0 because I also don't want an overload of black and white on the screen.

[Andrea B.]

P.S. I want to add that I use a monochrome setting with any converted camera when using certain filters. One prime example: a monochrome setting helps (me) immensely when shooting with a UV+Blue+Green stack. I was not always getting accurate in-camera WB with non-Nikons under some of these unusual filters like the UV+Blue+Green. So I went to monochrome and dealt with WB more accurately in the converter. Now YMMV on that. My non-Nikons are now rather old and that could be the reason for the inaccuracies.

We all do what works best for what we have to work with, right?

[Andrea B.]

Andrea's saying to take advantage of that to use the monochrome mode to prevent overexposures.

 

Actually it helps me prevent underexposures in UV because I make sure to move that mono hump to the middle (unless I'm shooting macro). There is quite a lot of underexposed UV photography in the world. I want/prefer to see some detail in UV-absorbing areas. The over- which is being prevented is oversaturation in the red channel (usually).

 

Hope all this helps someone!

[SteveE]

Panasonic has a new camera aimed at vloggers being announced on June 24, the G100

[Bill De Jager]

Thanks for the explanations, Andy and Andrea.

 

BIll, the monochrome setting only affects what you see in the viewfinder and the JPG. The RAW is unaffected by it, so there's no "turning it back into color," it's just processing the colors that are still present. ACR does not work for UV white balancing (RAW or no-RAW), so if you are getting odd results, that's probably one reason.

 

I didn't do the best job of communicating. Of course a true monochrome image, whether analog or digital, can't be turned into color except by "colorizing" which is only an approximation. What I meant is that the representation of the digital data as an image that we can view can still be done later as a color version rather than a monochrome version despite the monochrome setting at the time of exposure. In other words, I was thinking that the information on which pixels are assigned to a given color is retained in the RAW file even if the resulting image is rendered in monochrome (on the LCD and in the JPEG). My suspicions were correct.

 

I still think the monochrome setting must process luminance values in reference to surrounding pixels, to avoid having the Bayer filter pattern show up in the JPEG. For example, the red pixels would be brighter in monochrome than the blue or green pixels, for a red object in the image. But this doesn't matter for the RAW file.

 

What mystifies me still is something I've seen in my cameras and files and also mentioned above - a wide range of luminance values for each color when viewed in a color histogram turns into a much narrower hump of monochrome values when, for instance, saturation is set to zero. Is this because the monochrome image seen on the LCD has its pixel-by-pixel luminance values adjusted in reference to surrounding pixels, which would tend to eliminate the overexposure in the red channel? Just adding the three channels together ought to still leave the image with overexposed highlights.

[Andy Perrin]

Converting to monochrome is usually a weighted average of the three channels. It's not the sum exactly, each channel has a multiplier. For example, see:

https://en.wikipedia.org/wiki/Luma_(video)

[Andrea B.]

A quick experiment. Photograph the color checker passport in visible color.

Then in the converter save three different versions of the CC photo.

The three photos should vary in appearance.

• greyscale
  
• desaturated
  
• black and white (monochrome)
  

If nothing else, this little experiment helps to show why simple desaturation is not the best way of obtaining a B&W photo.

(This does assume your converter has some kind of B&W tool and greyscale tool.)

 

Black and white photographs are far, far from simple to make digitally. There's the matter of color filtration, contrast, zones and so much more on top of whatever weighting algorithm your monochrome setting uses (as Andy has referred to above).

 

***********

 

Andrea, is there any use for the Color Checker Passport thingy in UV?

 

Not really. Not in any serious way.

As we have mentioned a few times, the black patch on the CC Passport *can* be used for white balancing in UV or IR. It is not perfect but does get you in the ballpark.

 

 

...but occasionally I see people on here photograph the Color Checker and I've never understood why.

 

Birna and I and others typically set up a little test scene containing a white standard, a CC Passport and some flower and use that same scene for a test series of visible, UV, IR and other filtered photographs made all in one shooting session during which there is no particular reason to remove the CC Passport when one switches from UV to Visible. And I think we enjoy seeing those false blues from the CC Passport in the scene even though we don't make use of it for UV white balance or UV false color tuning.

 

It's certainly true there are no UV false yellows from the CC Passport. If you have a very accurate way of measuring UV white balance, then he UV false blues under a strict UV-pass filter can sometimes indicate the direction of the peak for that filter in a very general way (i.e., whether the peak is closer to 400 nm or closer to 350 nm). With a UV+Blue+Green filter there are both false blues and blue-greens. With longpass filters you can see some fun/strange color palettes after white balancing a photo of the CC P.

[Andy Perrin]

Birna and I and others typically set up a little test scene containing a white standard, a CC Passport and some flower and use that same scene for a test series of visible, UV, IR and other filtered photographs made all in one shooting session during which there is no particular reason to remove the CC Passport when one switches from UV to Visible. And I think we enjoy seeing those false blues from the CC Passport in the scene even though we don't make use of it for UV white balance or UV false color tuning.

So it's as simple as not wanting to change the scene between filters. Huh, well that explains a few years of head-scratching that I never bothered to ask about before!

[Andrea B.]

[dabateman]

But the color checker passport will fluoresce when hit with UV light.

I was going to use that for something. But now can't remember what.

[bvf]

Andrea, to get back to the original post ... I was just playing around with a trail camera (the things designed to automatically film animals either in daytime or at night using IR). By taping a U340 + S8612 in front of the lens I was able to take (poor quality) snapshots and video in UV. With this filter set in front of the lens, it switches the camera into night mode to film in IR, and the UVIR cut filter swings out of position.

 

There are a number of problems apart from IQ - the filter causes vignetting with the wide angle lens on the camera, and if the light source is ahead of the camera you get lots of reflection off the filter.

 

I've just got a basic model, but you can get others which can transmit their stills and videos.

 

This is probably more of an experment than a practical solution, but anyway here's a frame capture from the video. (PS: the temperature is noweher near 31C !)

 

[Dmitry]

One more option for some Olympus cameras with tethering support

https://dl-support.olympus-imaging.com/webcambeta/

[bostwickenator]

Just for giggles I pulled out the NEX5 and streamed the HDMI output to youtube as an end to end test. Basically even maxed out on the ISO my setup F3.5 with a couple of filters just isn't passing enough light to expose the grass at video framerates

[Andrea B.]

Alex, was that Nex5 a converted camera? Did you try setting a white balance? That might help a little bit.