Germain Wiseman Posted March 30, 2020 Share Posted March 30, 2020 Does anyone have data on the transmission of IR for the Nikon EL 80mm (old metal version) beyound 700nm? I'd like to do some multispectral imaging with this lens but can't really find any spectral data beyound 700nm. I assume that it doesn't just cut sharply at 700nm :-). Link to comment
nfoto Posted March 30, 2020 Share Posted March 30, 2020 I agree that any sharp cut-off is unlikely ... however, most lenses will show a focus shift given a wide enough spectral range. Even the legendary UV-Nikkor does that. Thus multispectral imaging might lead to some labour-intensive post-processing steps to align, or rescale, the images later. Link to comment
Germain Wiseman Posted March 30, 2020 Author Share Posted March 30, 2020 Yeah, I can image that there'll be quite a bit of focus shift through the spectral range, but I don't mind adjusting the registration of the images. Actually it'd be a nice challenge to setup that workflow. I often document art/artifacts under different sources and it'd be nice to not have to change the lens between UV, VIS and NIR. Link to comment
JMC Posted March 31, 2020 Share Posted March 31, 2020 Does the first post on here (https://www.ultravioletphotography.com/content/index.php/topic/3038-some-lens-transmission-curves/) give you what you need? While there's not much info on how it has been done, it would indicate that the 80mm el nikkor is good out to 1100nm without significant drop off. Link to comment
Adrian Posted March 31, 2020 Share Posted March 31, 2020 I have a Nikon technical brochure from the 1970's which gives the transmission as "370 - 700nm". I assume they didn't bother to test it for IR? I have always though that enlarging lenses would be designed to transmit mainly UV and blue, thus giving good results in a monochrome darkroom and red safelights. I will certainly test mine now for IR transmission to see what I get! Link to comment
Germain Wiseman Posted March 31, 2020 Author Share Posted March 31, 2020 Thanks, that link has the exact information that I wanted. I too have the Nikon Technical brochure and noticed the "370-700nm" data, which made me wonder if the IR transmitted well past 700nm or if it began to take a dramatic slope. Link to comment
ulf Posted March 31, 2020 Share Posted March 31, 2020 Thanks, that link has the exact information that I wanted. I too have the Nikon Technical brochure and noticed the "370-700nm" data, which made me wonder if the IR transmitted well past 700nm or if it began to take a dramatic slope.I think there is no technical reason to deliberately add an IR-transmission limitation.The specifications are most likely from the design scope to make the lens work well both for monochrome and colour work. As it is not optimised for IR-work too it is likely that you will see some focal shift and blurring from chromatic (IR) aberration. The possible decay in transmission, if there is any, will be much less than the sensitivity variations of your camera in IR. Link to comment
OlDoinyo Posted April 1, 2020 Share Posted April 1, 2020 It is very rare for any lens not to transmit freely in the near IR. That said, some lenses suffer hotspotting or chromatic aberration that make their use in this band undesirable. If there is no prior data on this lens, experimentation is the best course. Link to comment
dabateman Posted April 1, 2020 Share Posted April 1, 2020 It is very rare for any lens not to transmit freely in the near IR. That said, some lenses suffer hotspotting or chromatic aberration that make their use in this band undesirable. If there is no prior data on this lens, experimentation is the best course. Not affecting the Nikon 80mm. I have noticed some of my lenses do seem to take a nose dive into the IR.One being my Olympus 14-42mm R2 kit lens. It transmits okish into UV. Possibly down to at least 380nm. But was surprised to see major hit on exposure times with just a Lee 87C gel. This most likely is due to the type of coatings on the lens.Some Sigma lenses have been reported to noise dive into the IR to compensate for the high IR sensitivity of the Forveon sensors. Link to comment
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