Thalestris24

Hi

Well they are a business so have to allow for losses plus they work on new cameras so higher risk. They are short staffed too at the moment. I suppose 600 Euros isn't exorbitant for the amount of work involved. They don't guarantee perfect sensors so there will be imperfections. Hopefully flats will hide them

Louise

Thank you Louise   Yes, that's the method I've been using, pretty much.

Glad you're debayering is done

Thanks - it's taken them an awful long time! I hope it's not too long before they actually ship it. Patience is a virtue...

I believe they do a lot of their method under a (presumably low-power) microscope and in a flow cabinet. I imagine they use a hot air gun rather than a butane torch - the flame temperature must be potentially rather high!

Good luck

Louise

Hi Gina

Not sure if anything on the JTW debayering tutorial might help or suggest a way forward:

http://www.jtwastronomy.com/tutorials/debayer.html

They informed me a few days ago that they've successfully debayered the 1100d I ordered

Cheers

Louise

It's defo a high risk endeavour which is why I paid someone else to do it for me! Whether the mono 1100d is actually worth the cost remains to be seen!

Good luck again

Louise

Hi Gina

Just to be sure - have you tried resetting the camera settings?

Being cmos, the sensors are likely to be static sensitive so easily damaged that way - a possibility, maybe..

Louise

I wouldn't give up on it yet - there could be several reasons for the error. Maybe this might help:

http://www.magiclantern.fm/forum/index.php?topic=4105.0

Edit: oh ignore that, it's for Magic Lantern... Sorry.

I noticed you've posted here with error 70 before, Gina!

Louise

Well the cover glass is all off now - in lots of bits   Close inspection shows that all the gold wires are intact   I have now replaced the filter frame complete with filters to protect the sensor and gold wires while I reassemble the test rig and see if the sensor still works.  The cooling caused some condensation on the sensor so the image won't be perfect but the water marks will clean off after I've applied the epoxy resin - I'm not going anywhere near those fragile gold wires!

PHEW!!!  That was hairy

Rather you than me!

Good luck

Louise

Oh ok

Thanks

Louise

Sounds good Gina. I used a program called RawDigger to measure the brightness of the pixels.

http://www.rawdigger.com/

Hi

Interesting piece of software. Was wondering which version you have? Can it be used like ccdinspector?

Cheers

Louise

My results don't agree with your conclusion. Removing the microlenses halved the sensitivity of the photosite, but debayering quadrupled the number of photosites sensitive to Ha and SII. The net effect is double the sensitivity of the sensor which would halve your imaging time.

Thinking about it, it's only the sensitivity of individual pixels that count for the debayered sensor. Unless you 'bin' 4 x 4 (by some means) which would defeat the object of gaining resolution. So, on that basis, a debayered sensor could need up to twice the integration time... I suppose much will depend on the arc secs/pixel that one is imaging at as well as the particular target.

Oh my, it's getting late and my brain has had enough!

Louise

Well, it's certainly the case that the microlenses are only part of the picture (sic). Removing the CFA helps to make up for the microlense losses but this might result in a loss of contrast? It would be good if sensors had a flat response across the visible spectrum but they don't. Maybe something can be gained/compensated in processing? Maybe a custom software debayering might be useful? I'm just thinking aloud

Cheers

Louise

Hiya

True, but for a daytime scene it can be an indoor still life or something A long exposure night time view would be trickier but a widefield sky view probably won't change much. At the end of the day, I'm only looking to see roughly how different the responses might be. Say I do a 2 minute exposure with both cameras but find the mono is a bit fainter but can get a similar result to the colour camera by exposing for an extra 20s. That will be good enough for me. I don't much care about gathering precise data, I only want to see if the mono camera is still useable, really.

Cheers

Louise

Ah, yes, you must be right as it's absolute QE. For my own interest, I was thinking of just doing a simple, subjective comparison. Two different cameras but with the same lens and same scene and with same manual exposure and ISO. It's surely the result that counts . I don't have any narrowband filters at the mo. I thought I'd do some short daytime exposures and some long astro exposures. I could simply desaturate the colour images and just compare side by side. I'll think about that a bit and I don't have the debayered camera yet. Hopefully it won't be much longer!

Cheers

Louise

Edit: of course, it will be cloudy when I get it!

Sort of. If you look at QE charts of OSC sensors, you'll see the R, G & B pixels overlap each other. Thus, the G and B pixels are still capturing some of the Red SII light. It's not like mono sensors with RGB filters where you get a sharp cut off between the colour bands.

Hi again

Yeah, that's what I was thinking. Makes it hard to do 'before' and 'after' comparisons. Also, the green region in colour sensor graphs are the response of two pixels rather than just one - Oh, I think someone's already said that!

I think if the debayered version performs reasonably well then that's what you'd hope for and can be happy

Cheers

Louise

Indeed

Here are the results from my tests using Ha, OIII and SII filters. You can see that from my sensor, removing the microlenses roughly halved the sensitivity of the photosites. But you can also see that, since all photosites on the debayered side are sensitive to the filtered light, the sensitivity of the sensor improves by 75-110% for SII & Ha (ignoring signal recorded in the B & G regions). But the results from the OIII are a bit more interesting. This showed no improvement in the sensitivity of the sensor after debayering (ignoring signal recorded in the B & R regions). Also, if you could use the signal from the B pixels, the debayering process actually makes the sensor only 75% as sensitive as the original with microlenses.

Here's the table of results:

DebayerResults.png

Hi

If I'm reading that right, when using the original sensor with say light via Sii, which is just a narrow band of red light, then the responses from G, G2 and B pixels are really colour 'noise' since ideally you'd want the G, G2 and B pixels to be 0?

Cheers

Louise

Hi

When I (eventually!) get the debayered 1100d I ordered ages ago... I'll be able to do a direct comparison with my standard, unmodded 1100d. I'll probably just do some shots through my canon 75-300mm lens, initially. At the moment I'm not sure how best to process the mono raw files but I'll figure something out

The mono 1100d has been ordered from JTW but they are a bit slow...

Fwiw, during discussions they said:

"The debayered sensor loses the microlenses but gains resolution and sensitivity. There is a bit loss of about 30% from the microlens removal but an even bigger gain, just under 1 stop is about average."

The proof of the pudding, as they say. 

I'm not expecting the mono 1100d to then miraculously become a great camera - it will still be uncooled and noisy. It will still need dark and flat calibration frames. There are bound to be imperfections from the debayering - flats will be essential to help cover them up, and for vignetting, of course. But, hey, it'll still be 4272 x 2848   That alone is pretty cool

Cheers

Louise
 

Are you sure it's not light leaking through the viewfinder on the camera , it's a more common problem.

 

There's a cover for it on the camera strap.

Not in my case! I have a ccd... Light definitely leaks in through the mirror end but it probably wouldn't matter in normal use i.e. in the dark.

Louise

Hi

Funnily enough I noticed this the other day when testing out the new Ascom driver for my qhy8l. I was taking sets of darks during the day and was dismayed to find that long exposure darks weren't! I put black bags and even foil over the front end - over the endcap. There was still some light leakage so decided the mirror end needed covering too. I was also stretching the darks looking for signs of amp glow and was surprised to find I could stretch them to white. Never tried it before and had assumed that if an image was totally dark that it couldn't be stretched. Of course, I'd forgotten the bias noise would still be there! This realisation prevented me from becoming paranoid about light leaks - I think!

Louise