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UltravioletPhotography

Credit River + Schott RG1000


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eye4invisible

It's been a very wet spring here in Ontario and parts of Quebec, leading to localised patches of flooding.

 

This is a shot of the Credit River in Mississauga. At 1000nm, you can clearly see the black water contrast against the flooded white grass in the bottom right-hand corner of the photo:

 

post-116-0-05576000-1558972264.jpg

 

And, no, this isn't a drone shot - it's just taken from a high-up hump bridge.

 

 

Not sure what kind of fish this chap is trying to catch - the swollen river was flowing very fast:

 

post-116-0-97168000-1558973085.jpg

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Nice spot indeed, and lovely shots.

Do you have 830nm or 850nm? If so, do you notice much difference between those and 1000nm?

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eye4invisible

Nice spot indeed, and lovely shots.

Do you have 830nm or 850nm? If so, do you notice much difference between those and 1000nm?

Thanks, Steve!

 

I actually have a Neewer 950nm filter, but it's not as contrasty as your RG1000. I shot these using the "MC" picture control for in-camera B&W. Even without MC, with the RG1000, the images render as near B&W with the slightest hint of blue, whereas with the Neewer, the cast is more blue in colour. I like the contrast of the RG1000.

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Hi Andy, One difference to be noted between RG830/RG850 and RG1000 would be the exposure time, RG1000 requires more exposure time.

When I have photographed water, notably a glass of water, the water looks darker using RG1000 than with RG850.

I have not noticed a difference in monochrome between RG830/RG850 and RG1000, but I do see a difference between RG780 and RG830/RG850, with RG780 showing an ever so slight amount more brown tone.

In fact, most Bayer filter transmission graphs generally show the blue, green, and red sensitivity becoming equalized at about the 850nm range.

Once again, nice shots.

 

It would be anyone's guess what the exact plot would be of the Neewer 950nm, but lets say they are using a standard 50% transmittance at 950nm, but we don't know what their thickness is, or how real that is.

Schott rates and 'names' all their filters according to their Ti (internal transmittance) graphs in their catalogue (pdf).

However, a straight T (transmittance) graph may be closer to actuality.

Schott uses the 3mm thickness for their longpass filters at 50% transmittance. So the 'nm name' of their longpass filters is the nm number at which their Ti plot of their 3mm thick version crosses the %50 point.

So here I compare the 3mm Ti thickness of RG1000 with the 2mm thickness you have, and also the RG830 and RG850 2mm Ti thickness graphs,

and in black I show the more likely plot of the T version of the RG1000 2mm, which would put it at about 980nm at 50%.

You be the judge. I am betting on the black line.

post-87-0-56681000-1559098691.jpg

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Andy Perrin
I have the NEEWER filters, and just as a point of reference, the Hoya R72 (which I trust) looks noticeably different even to the eye without a camera (because we can see the red end of the tail) than the NEEWER 720nm. So I think they are probably pretty different. It would be nice to have a real spectrum for them, though.
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Andy Perrin
UlfW, that link says (if I follow the text properly) that the photographer is using an unconverted camera. And the NEEWER results at 850nm apparently have color in them? I don’t trust the results there. My NEEWER 850 shows no color at all when white balanced.
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Indeed, the author doesn't mention the camera conversion. Makes it sound a little like they don't want to 'sacrafice' a camera for conversion, but I don't know if that means a dedicated IR nm conversion, or what?



On the other hand, I find it a little impossible to think those photos they show are done with a stock camera. I don't see any motion blur... so...

They say a Nikon D610, right? I rather doubt you would get the sort of photos shown with a stock D610.

But indeed the information about the camera seems lacking, unless I missed something, and I usually do miss something.

I like the really cool cityscape header, what city? Had to Google it, Shanghai.

 

OK, so here is a D7000 stock (right), used with 830nm longpass (B+W 093), long exposure, makes it look like some higher 600nm range longpass with color.

This is the product of stacking 830nm + BG, you will get about the same if you use a long enough exposure time.

post-87-0-38513700-1559109646.jpg

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Andy Perrin
Yeah, that result (yours, Cadmium) makes me think that the blog is using a stock. The color must be a visible leak? Like perhaps the 830 is blocking most of the visible except for deep red, and the BG is doing the opposite, so you are left with a small bump of transmission in deep red, perhaps somewhere in the upper 700nm range.
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I tend to lean the other direction, given that the pics all look so sharp. With a long exposure you would get more movement, blur I think, and no monochrome with a stock camera. A long enough exposure time will start to see visual red even through an 830nm filter...
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Andy Perrin
That’s exactly what you do see? Are we looking at the same pic? It’s that orange sky with blurry trees.
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UlfW, that link says (if I follow the text properly) that the photographer is using an unconverted camera.

 

Sorry, I missed that by jumping directly to the filters comparison section.

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That’s exactly what you do see? Are we looking at the same pic? It’s that orange sky with blurry trees.

 

Your right, those three Newer 850nm shots have the long exposure blur.

I guess I was focusing more on the other shots being so clear...

Yep, maybe disregard that link, they should be using a full spectrum camera for that.

 

I tend to think the site is China maybe, and I am more an more skeptical of things from China.

 

If you use longpass IR filters on a stock camera then you are not really getting photos that are the intended NM, similar to if you stack a longpass with a Baader U, you will be seeing IR instead of UV, with a long exposure time.

 

I want to see some more RG1000 shots from Andy Broomé.

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Cadmium I bought some of these filters back in 2009, when I was still in a lab.

 

My Neweer 950nm maybe different then yours, but the spectra is as follows:

post-188-0-52996900-1559251938.jpg

 

My BW 093 filter spectra for reference:

post-188-0-74636100-1559251952.jpg

 

My Neweer 830nm filter at 32mm size that I glued into a SD14 sigma holder:

post-188-0-24182900-1559251974.jpg

 

 

The sun no longer shines here. But if it does one day, I can take a photo with these and other IR filters if you want to know what they look like.

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eye4invisible

Andy Broomé has that filter, not me.

Andy, post more photos when you do some.

Will do. It's a nice sunny day (for the moment!) here. I'll bring my Neewer 950nm and the RG1000 along, and take some comparison shots, so you can see SOOC the difference.

 

There's definitely a longer exposure time required for the 2 filters - not the sort of filter you'd want to attempt to use on an unconverted camera. I usually shoot with Aperture Priority Auto, so I'll also post the shutter speeds as well to see how much extra exposure time is required between the 2.

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