I decided to put my A7R IV on the bench to give it some new life pulling triple-duty as an H-alpha sensitive astrophotography beast, an IR maven, and of course it's usual role as a great high-res all-arounder. How am I making this happen? By combining a full-spectrum modification with a bunch of magnetic clip-in filters that I purchased from Kolari Vision. The filters are in the mail, so I modded the camera in anticipation and filmed it for the reference of anyone who is curious.
There are only a handful of Sony A7 series cameras that can be properly full spectrum or astro modified, due to an internal IR light source. As of this upload they are the A7, A7R, A7S, A7 III, A7R IV, and A7C. Any other A7 series camera that is modified will experience internal light pollution visible during long exposures.
The Nidec Copal shutters used in Sony's cameras use a little IR LED/Sensor pair (optocoupler) to sense the open or closed position of the lower shutter curtain actuator. Nidec Copal uses IR LEDs of different wavelengths in different shutter models, and unfortunately in some cases these IR wavelengths fall into the detectable range of a full spectrum or astro modified sensor. The IR light shines out from inside the shutter housing, casting itself across the sensor and ruining images with a nasty magenta smear. It even defeats coating-based IR-cut filters such as "H-alpha" filters as it comes in at such a shallow angle that the reflectance characteristics of the filters shift and are unable to stop it. Why is this not normally a problem? Well, this IR spill is usually screened out by the IR absorbing filter (the green/blue-ish one) that we are removing, which can soak it up from any angle.
This was my first time inside the A7R IV, however the design sensibility is pretty consistent with the camera's predecessors, most of which I've worked on. It had been a minute since I've been inside an A7 series camera however, so there was a bit of exploration involved. I was pretty cavalier at certain points, which was due to the fact that I have a no-questions-asked full replacement warranty (a "throw it against the wall" warranty as I like to call it). But it was a successful mod and I won't be needing to leverage that. I'd always suggest moving slowly and cautiously when working inside any expensive electronics.
The break in the video toward the end (before final reassembly) was due to me getting distracted and forgetting to reconnect a flex cable. I had to disassemble the camera again to fix the gaffe (off camera). Let me know in the comments if you can spot my screw-up.
I also had some issues with my anti-static glove material coming off on the tape holding the NFC flex cable to the main board, which I tried to rectify by lightly cleaning the tape adhesive with acetone. The gloves are woven through with carbon fibers and the last thing you'd want is a bunch of rogue conductive fibers making connections between the various SMD components the tape was stuck to. When I dove back in to reconnect the flex cable mentioned above I ended up replacing the original tape with some fresh high-temperature electronic masking tape. And good thing I did, as a look at the old tape under a microscope revealed a plethora of black carbon fibers. It never pays to be lazy when working on a camera.
And apologies for the poofy hair obscuring the view at certain points when I lean in for a closer look! I had just washed it and it was a giant puff ball of frizz with a mind of it's own.
Original footage was 24fps, final video is sped up 10x.
Find this helpful? Glad to help!
And if you're ever in the market for a shiny new William Optics scope, a Fornax Mounts LighTrack II, or maybe a QHYCCD camera, head on over to FerventAstronomy.com and take a look. Based in Canada, but we ship worldwide.
Clear Skies!
7 мар 2022
