If you have been using your digital camera for astrophotography, you’re probably aware that there are special astro variants of some of the more popular cameras. But how exactly are these special variants different, and can you modify yours?
The answer is in the UV/IR cut filter sitting on top of the camera sensor. Camera manufacturers install these filters to essentially cut out most ultraviolet and infrared light, which is deemed irrelevant for terrestrial photography. You can absolutely modify your camera to remove these filters, which will enable you to gather light from a broader spectrum and get better astro photos with more detail. But if you have ever looked at the options when deciding which modification to get, you may have been overwhelmed and decided that this may not be for you.
In this video, Nico Carver, aka Nebula Photos on YouTube, breaks down the differences between the many different types of astro camera modifications available. After a brief explanation of the camera’s internal filter stack, we get an explanation of the three main types of astro mods. Suffice to say that they all involve removing all or parts of the OEM filters for more sensitivity in the infrared spectrum. It's extremely helpful to have examples of these modifications, which he provides while including both an unmodified camera and Canon’s own EOS Ra (which is modified from the factory).
I, for one, found these comparisons eye-opening, as I have always been wary of modifying my camera for the fear that I would get the wrong one and have to live with my poor decision. I was pleasantly surprised that the simplest and least expensive mod performed admirably when compared to even the most expensive EOS Ra, which is modified in house by Canon and carries a hefty premium over the non-modified EOS R. But what was most surprising to me was that depending on which modification you choose, you can still use your camera to take pictures during the day! So, with the correct combination of filters and/or custom white balances, it is entirely possible to continue using your camera as if you had never modified it. I think I may have to take the leap and try this out. What about you?
Not all cameras are 100% suitable for modification. For example, modified Sony A7Rii and A7Riii can have artifacts in certain situations.
Good to know! Thanks Christian!
Well most cameras aren't great for that kind of astrophotography in the first place because they cook RAW files with noise reduction algorithms.
Thanks for the info! I wonder if you could elaborate?
I'm not sure about RAW cooking, but if you look at Kolarivision's website, under each brand they list which models have issues: https://kolarivision.com/product-category/full-spectrum-conversions/
All Sony cameras apply noise reduction algorithms to the RAW files which can't be disabled by the user.
Early Sony used to have the infamous "star eater" algorithm which made some models totally unusable, that is gone now but they keep tampering with RAW files.
It isn't super noticeable in landscape astro (but they still can ruin star colors and create artifacts) but it can cause problems for deep sky since, apart from the artifacts, it makes dark frame calibration impossible.
Unfortunately pretty much every major manufacturer uses similar algorithms, maybe less invasive than Sony's but they're still there. The only big exception afaik is Canon, and that's one of the rasons it's till the preferred brand for astro imaging.
Very interesting!
Because nearly all dedicated astro camera uses Sony sensors, so I'm assuming its not the sensors fault, its purely the Bionz image processers in Sony cameras. Do I understand that right?
Exactly, it's purely software processing done to the data that has already been converted to numbers.
Different brands using the same sensors (like Nikon, Panasonic, Sigma, Leica sharing the 24mpx BSI) all have different NR algorithms, and even in Sony's own cameras you can measure different behaviour with different exposure times since the NR only kicks in beyond 3.2s of exposure.