RGB24 or RAW16?

[Demonperformer]

With (dare I say it) clear skies promised for tonight, I am thinking of getting out with the new scope(star71)/camera(ASI224) combination and giving it a run for its money. Been looking at the settings in sharpcap and there are 4 options: RAW8, RGB24, MONO8, RAW16. I want to shoot in colour, so MONO8 is obviously wrong, & RAW8 I guess is also not going to improve results any - making my choice between RGB24 & RAW16. I'm guessing that RAW16 is my best option - as long as that still captures in colour. I'm just a bit confused about that, when an alternative states RGB, which is definitely colour.

If anyone can clarify before I go out and have to experiment (= waste valuable imaging time), much appreciated.

Thanks.

[LightBucket]

The RAW modes are still colour but will need debayering in DSS or whichever programme you use, with RAW you get 100% of the data, the RGB is, I think, is a compressed colour image, so you won’t get all the data and won’t be able to process very much...so RAW is always you best bet, just like using a DSLR, you shoot in RAW and then debayer and process... HTH  

edit, forgot to say, yes RAW16 is your best option...

[Demonperformer]

Thanks.

That was my inclination, but it is good to have it confirmed.

[Demonperformer]

BTW: How are you getting on with the focal reducer?

[LightBucket]

Just now, Demonperformer said:

BTW: How are you getting on with the focal reducer?

Hmmm, haven’t use yet, sorry to say, but it sure will get used..  thanks very much, it’s in superb condition too...

[JamesF]

RAW8 would be preprocessed into RGB24, so they're not too far apart.  The difference is that if you take the RAW8 data then you can choose when the colour conversion is done and what algorithm is used.  There are probably dozens of different algorithms for converting raw colour to RGB depending on the required quality of the final image and the time it takes.  Obviously if the driver code is doing the conversion (which I'm fairly sure is the case for the ZWO cameras), there's got to be a bit of a compromise on quality to ensure frames are processed fast enough.  The data coming from the actual hardware is the same in each case as far as I'm aware.

RAW16 (which I think is actually only 12-bits per pixel rather than 16 in this camera) increases the amount of information available per pixel by 50% at the cost of taking twice as long to transfer from the camera (which limits the frame rate compared with RAW8/RGB24) and increasing the disk space required to store the captured data (which also has an impact on speed).  If you can live with those constraints then you might prefer to use RAW16.  You can always convert it back to RAW8 later if you wish.

Personally I'd always go with the raw data if it's going to be processed after capture because it leaves the greatest number of processing options available.  And if the entire system could handle RAW16 at the frame rate I wanted then I'd use that.

James

[JamesF]

1 hour ago, LightBucket said:

RGB is, I think, is a compressed colour image

It's not compressed as such.  RGB24 is an image with three colour components and 8-bit values to determine the contribution of each colour to each pixel (so 24 bits in total).  It actually triples the size of the 8-bit raw colour image from which it is generated.  The algorithms for converting raw to full colour generate the "missing" data for, say, a pixel position where the colour mask gives a red pixel by combining the values from the surrounding pixels to give an estimate of what the green and blue components would have been at that point.

James

[MarsG76]

I too vote for RAW16... RAW8 is same as RGB24 (8 bit each R G & B channels)... RAW16 is 16bit per channel delivering a container and possibility of up to  281,474,976,710,656 colors and shades as opposed to "only" 16,777,216.

At the sacrifice of much more data, but also much bigger frame sizes limiting the FPS...