petrochemist

I think you've got that backwards. He chose gear for his subjects not the other way round.

BTTC grid in IR by Mike Kanssen, on Flickr

The reports I've seen vary a bit but suggest Silicon becomes transparent to NIR between about 1100 & 1150nm. which ties in with your band gap. With a modified camera 960nm filters certainly work & they can even work on some unmodified cameras such as my K100d, not only that but I can see through it in bright sunshine! Yellow, orange, red & infra red filters are normally classed as 'long pass' filters, the wavelength quoted typically being that at which 50% transmission is expected. I've recorded spectra for quite a number of these on the UV/visible/NIR spectrometer at work & haven't come across any that don't transmit well at 1100nm (the top end of the spectrometers range). most of them have fairly rapid transitions, giving little transmission 30nm below their switch over wavelength & giving near full transmission 30nm above it. The 960nm filter I have is however a much more gradual change extending over 100nm either side of the 50% point IIRC it actually transmits more below 820nm than my 860nm filter. The Kodak/Wratten handbook lists some yellow filters that are not long pass ones, but I've not picked any of these up yet. Blue, green & even UV transmitting short-pass filters generally transmit significant NIR as well, but this is somewhat more variable - I've actually got three Wratten #58 filters/gels between then I have one with little NIR, one with lots & one capping NIR to around 50%. All are fairly similar in the visual spectrum. With a typical UV-pass filter most 'full spectrum' converted cameras will see more NIR than UV, this being got around by fancy coatings or by combining multiple filters (which severely reduces the UV transmission) I can't justify £200 for a coated filter, (let alone the £1000+ for lenses designed for UV) so UV imaging remains a unconquered challenge.

On the Bayer filter spectra I've seen the red channel is significantly more sensitive than the other channels in the 680 to 780 region, above about 850nm all three tend to be fairly close. When it comes to taking shots red/orange is common for a 720 or 760nm filter but I have noticed my 960nm filter tends to produce purpleish colours SOOC. 'Normal expectations' among the uninitiated would tend to suggest the green channel would pick up more than the blue channel but this is not the case. Many people think of light as being made up of red, blue & green, (as our eyes see it) when in fact it is a continuum of subtlety different wavelengths working in spectroscopy this true nature is sometimes brought clearly home to me - measuring lead at 283.38 nm seeing quite a different result than would be seen at 284nm. :eek:

For a non modified camera that's pretty sensitive, my K100d is only about 2 stops more sensitive. here's a quick example with the unmodified K100d (1/20s, f2.8 iso 200) London IR by Mike Kanssen, on Flickr but at least 10 stops less than my modified bodies. I've found one example with the modified GF2 using a R72 that used 1/800, f/7 & iso 100 - I make that 11 stops, but I just assumed any fractional stops where half stops: sml P1150505bw by Mike Kanssen, on Flickr My false colour IR tends to be very much more saturated than an unmodified camera can manage often containing both UV/deep blue & IR sml P1150800h by Mike Kanssen, on Flickr (Sorry that's drifting of topic).

A degree of similarity certainly, but as a mirrorless user I can assure you an EVF is just one of the special features of mirrorless cameras. The very short registration is very significant I've never been able to use rangefinder lenses with my DSLRs, or connect them to my Newtonian scope... One of the big advantages of mirrorless designs is lost with SLT designs, it seems more like a worst of both worlds compromise.

I don't like them, but they are in no way like mirrorless they have none of the advantages of mirrorless bodies and share many of the disadvantages of DSLRs and then add a few of their own... In case I come over as a mirrorless only fanatic I'll point out it was one of my DSLRs I was shooting with today.

It is equally true that the shadows of your second frame will be filled by your first... It makes no difference which order they are shot in.

Hope it goes well for you. I've found IR rather addictive :)

I haven't a clue how responsive unmodified Fuji cameras are to infra red, (you can get a bit of a clue using a TV remote) but I suspect they won't be particularly good, as I've not heard much about them being used. (I spend too much time on IR specific forums too) My old Pentax K100d is renowned for being responsive, despite it's relative low ISO range I've often been able to manage hand held IR (even with a 960nm filter). Newer Pentax camera are considerably less sensitive as are AFAIK all canon models. I'd recommend getting a cheap Chinese 720nm filter first. I find the quality of these acceptable despite the price and you'll be able to access how you camera responds. The B+W 093 is an 830nm filter which MAY only transmit wavelengths beyond your cameras sensitivity and will probably give quite long exposures probably several minutes. A 720nm (R72) can be used for colour but it is one of the most common filters & is usually used for monochrome. For many years I've used converted cameras for my IR unless I've specifically wanted really long exposures.

...as well as a good explaination of why it became significant. Captured english archers had their fingers amputated to prevent them using their longbows. The symbol was a clear I'm still a threat to you.

If the photo is being taken for artistic use then emotionally correct is better, but if you're doing product photography or scientific work them accurate is almost certainly going to be required. Of course emotionally correct can be a moving target depending on the viewer - I've found most people prefer a more vivid colour than I do something I often find garish. I generally prefer more subtle colour levels, that my Pentax cameras refereed to as 'Natural'. To some it seems more is better is a moto they try to apply to everything! I shoot a fair bit of colour infra red, where the colours seen are quite different from visual - I guess these could be considered emotionally incorrect - again I prefer more muted tones, but can find several very different versions of the same shot work for me. I can also put my hand up to admit I've shot things with the wrong white balance on more than one occasion. Sometimes deliberately to emphasise the emotional colour & at other times by mistake & effectively lost the shot.

Are there really any 645 systems without a good portrait lens? Portraits would have been a major part of the role for any such camera. Agree 100%, if you want multiple backs for use in studio, there no reason not to simply get a spare body or two. They're reasonably affordable these days. Edit: I see Joe's already added that suggestion - note to self read to the end of a thread before replying... :D

I think it's more a reflection of the very first video camera EVFs which were certainly laggy & low resolution... I've not used the latest generation EVFs, but have seen considerable improvement over the models I have used. Even the G1 proved adequate for most styles of shooting, though an OVF was clearly better at that point, if fast action was wanted.

Sorry about the rope in the way! RN trike by Mike Kanssen, on Flickr

Grace Dieu Proiry (Infra red) 10 by Mike Kanssen, on Flickr

Shot with a 1930's Kodak 12cm astigmat on a Pentax K100d (mounted via bellows) black scorpion 2 stack by Mike Kanssen, on Flickr

I find for most of my shooting mirrorless suits me better, but as my cameras are all older models I've certainly found EVFs are slightly less comfortable for motorsports & so I still use my DSLRs for that. Any of my mirrorless cameras are still usable for motorsports (even the ancient G1) and I've never been able to determine exactly what it is with the DSLRs that's preferable - viewfinder lag has not been an issue for me. It could just be that I don't have good native AF super telephoto lenses for my mirrorless cameras...

That elephant is certainly not in my room. I've used a wide range of mirrorless cameras sometimes for intensive shooting at motorsports. Sensor heat up has never been apparent on any of them. It might become an issue if you leave the camera on endlessly without shooting - but I didn't do that with my DSLRs so don't see the need to with mirrorless cameras. 10 minutes left on isn't a problem.

I understand the no words idea was to prevent the threads from becoming endless discussions about the images - often the case on other forums. A short entrance before the image can IMO be ignored easily & can help make the image more interesting. I usually come across threads via the 'new posts' option where the no words listing is not obvious. because of this in my early days on the forum I replied to some with comments.:oops: I suspect this restriction has reduced the time I spend on this forum, as some discussion on images is something that helps my photography evolve.

Yes that's clearly smaller than M39! Tmo me it looks like it's 33mm between the inner parts of the threads which would be what you expect from a M34 x0.5 thread. Metric threads are designated according to the measurement across the outside of the male threads, the diameter between the inner edges of the female threads will be about twice the pitch smaller than this (actually slightly smaller to allow some movement between threads 0.2mm leeway is typical for the threads I've measured). M34x0.5 is one of many threads around this size that have been used in photography. I know of M32.5x0.5 threads on some enlarging lens filters (as well as Copal 0 mounting threads), m33 threads of unknown pitch used on early Industar 50-2 models... This region is also one where pitches are not standardized in the way they are on larger filters pitches of 0.5 & 0.75 are used seemingly at random between 25.5mm & 43mm with both being used on different m37.5 filter threads. Looking at my notes on optical screw threads I've found an amazing 29 different threads between 25mm & 40mm diameter, and the chances are quite high there are several I've not come across! It's not easy checking the pitch of very fine threads like these especially in female form. If you get a metric pitch gauge you can supposedly use it to judge the pitch but I find visual comparison with filters of known pitch often works out easier. filter threads between 43mm & 77mm are nearly always 0.75 pitch, if it looks finer than this it will be 0.5 pitch (as long as it's a metric thread). NB the Leica M39 screw mount is a strange mixture of metric & imperial despite being very close to 1mm pitch its M39 but at 26tpi (tracks per inch). Similar odd combinations might be seen in early Lietz filter threads :eek: Perhaps not a solution you'd want to use on a Leica lens but I've heard of options like using sticky foam to pad out a smaller stepping ring so as to fit unusual threads. I have a couple of old sprung filter holders (one sold as 'Handcross' but the other having no identification) that could be used to attach filters - again I might be reluctant to fit them to a Leica lens & risk scratching the paintwork. The ideal solution might have been the smallest size 'Revoring' adjustable stepping ring, I backed on kick starter a year ago, but it seems so far it's only the larger sizes that are being made so far. So much for the November 2020 dispatch... Edit - Typical taken far too long typing & you've got the answer already!

All four of the versions listed on the all photo lenses database have m39 filters I included the macro model (two versions include Leica M variants & screw threaded variants) Hopefully the pictures will help you identify which if any of those included is your model.

Normal light meters do not measure NIR so for film all the many sources I've got state you must bracket widely. So much easier with my converted digital cameras - the meter with the same sensor that takes the image so it's nice & consistent.

All hanging until a few micro second previous to the shot (part still is) balloon 7 by Mike Kanssen, on Flickr