Infared IR Conversion Considerations and Options

[dudski]

I'm curious, Craig, are you planning on using the converted camera for macro photos? If so, please share.

I've had an IR-converted D50 for a few years now (filter bought from lifepixel, home conversion) and have taken tons of landscape photos with it (examples here: http://www.pbase.com/damian_turski/indo ... n_infrared), but never used it for any macro stuff.

I've also had some experience with the dreaded hot-spot, but this was with a sigma 10-20mm. Its something that is very apparent when you have colour in the photo but much less so for B&W.

ETA: if you're looking for an inexpensive lens that works great for IR (at least with the D50), the el-cheapo nikon 18-55 (the D50's stock lens) is great. From what I recall, you won't even need to adjust the focus on it (ie the camera's autofocus does a good job) as long as the camera has not been calibrated to another lens

[Craig Gerard]

Damian,

I enjoyed looking at your IR images.

I've taken an alternate course regarding the Nikon D50 and opted instead to convert a Canon 50D for reasons of capabilities and practical considerations available equipment i.e. Canon glass.

Regarding mäcro, yes I do intend to explore this area with IR.

I have elected to have the DSLR converted for 'Full Spectrum' also described as UV+Visible+IR or UVIR+Visible (and possibly other definitions of which I am unaware).

The internal hot mirror (IR cut filter) of the Canon 50D will be replaced with a custom manufactured, full spectrum (clear) Schott glass filter. I'll be having the conversion applied by one of the recognised companies who deal with such matters.

I do not currently possess the technical knowledge or ability to explain this in more detail, but as has been mentioned by other members in previous posts, the 'Full Spectrum' approach provides the most versatility.


Craig

[Photo-DIY]

The problem with the full spectrum conversion is the dark viewfinder when used with an filter that only transmitts infrared.
Liveview is ther a big help, but I am not sure wheter Liveview will help with probably not much IR light/radiation + small effective aperture in micro and macro photography.
And to change filters is probably problematic too.

But I have to admit, that my versatilely way of changable filters behind the mirror would´t helpt too, because lack of IR index in most of my micro/macro lens combinations.

[magus424]

I only use live view through objectives, it can amp up the light for the screen very nicely.

You also aren't stripping out that much light when you consider that the glass over the filter isn't stripping it out anymore - you're just bringing it back into a normal amount but with a shifted spectrum - it should be visible just fine.

[Craig Gerard]

Most of the following information was kindly provided by another member and it seems an appropriate time to introduce it to this thread.

Full Spectrum and a filter opaque to visible light is not opaque to the sensor.. so Live View gives you the image as seen (with the exposure appropriate for the IR light) at the display...

You should have no problems viewing IR images using Live View (with the appropriate hood so you can see the LCD monitor) in daylight.

Full Spectrum means that you are only limited spectrally by the transmisison characteristics of the sensor.. most CCD, CMOS, etc.. are sensitive from the UV at around 320nm through IR around 1200nm.. but the transmission usually drops off quickly from 350nm to 320nm and from 1000nm to 1200nm..

So for an 830nm longpass filter (passing 830nm to 1200nm say) the exposure is better than a 1000nm longpass (passiing 1000nm to 1200nm) as the sensor sensitivity is limiting the exposre.. so you are forced to longer exposures at the limits of the sensor..

My 830nm longpass conversions (or full spectum and an 830nm longpass filter) are probably the best for pure IR work.. (this is the B+W 093 filter)

As far as exposure with Live View.. even though there is some amplification at the display you should see just how good the image is.. of course, you can take a shot and adjust using the histogram which is what I always do... I mostly use Live View for focusing and framing.

Another quote from a different source.

Strongly consider converting a camera body that has Live View 10x and an RGB histogram. Even if you recalibrate AF, you will have other lenses that will no longer AF properly at IR wavelengths. MF with live view is the only universal solution, as you need to see what the sensor is seeing. An optical viewfinder will Never see IR on a converted camera. Similarly, IR exposure can be way off depending upon the color distribution in your composition. A luminance histogram is not very revealing, you need one that displays RGB and watch the red channel for clipping.

[johnsankey]

See http://johnsankey.ca/multispectrum.html and
http://johnsankey.ca/insectvision.html
for exposure notes etc. with UV-visible-IR filters.

Unless you have a CoastalOpt lens, you have to use LiveView to focus IR because the focus points will be different than for visible. As long as the viewfinder is blocked to prevent stray light upsetting it, I find auto-exposure works surprisingly well for a first try, getting it close enough that the histogram display tells you the adjustment need for the perfect exposure.

[Craig Gerard]

John,

Thank you for the links and detailed information therein.

Most appreciated.


Craig