Debayered 1100d Comparison

[Thalestris24]

Hi all

Finally got my debayered/mono 1100d (actually a 'Rebel T3') delivered today So thought I'd do a very quick comparison with a standard 1100d.

Not very scientific, but I wanted to check it was working ok. Shots were taken with a 75-300mm zoom lens set at 75mm. ISO was 100. I exposed in Av mode which gave an exposure time of 1/395s for both cameras. Converted the cr2 files to jpg and reduced image size to 25pc of original.

As I expected there is some loss of contrast with the mono camera, presumably because of the loss of the microlenses. The mono version has a full-spectrum mod so will pick up UV and IR.

Mono:

Mono converted to b/w:

Normal colour:

Normal colour converted to b/w:

I guess I need to do a custom white balance to get rid of the pink tones although I'm not quite sure why they would be present. There doesn't appear to be any overt loss of sensitivity but a proper scientific test might reveal more. Still, it seems to work ok! . Not sure when I might be able to do some astro imaging with it.

Anyway, there you go.

Louise

[PhotoGav]

The main difference I see is that the mono camera has two old ladies in the lower left hand quadrant of the frame. Should be easy enough to remove with flats....

Can't wait to see some results with this camera - it's a very interesting idea converting the DSLR into a mono CCD essentially. How about cooling?!

There's a spanish chap (sorry, can't remember the name) who has posted some fantastic images on here taken with a debayered mono DSLR. It's almost tempting!

[russellhq]

I guess it's pink because the camera still thinks there's a CFA over the sensor and is adjusting accordingly when converting from RAW to JPG. A custom white balance should fix it as you say but you'll still be applying a debayering routine, which I think you want to avoid.

You need to open the RAW file without applying the debayering routine. I use fitswork4 to do this. There's also dcraw that will do if you're happy to use command line.

[Thalestris24]

Heh heh

Amazing how one camera picks up old ladies and the other one doesn't! There is a difference though - I'm not sure how much is due to increased red/infra red sensitivity. That plus UV might have contributed to the difference in contrast but I'm fairly sure it's the microlens removal that's the main culprit. It may not matter that much. How it will perform with low light / long exposure is still to be determined. It will never be comparable to a ccd but can excel in terms of resolution. There are people in the diy section that are experimenting with peltier coolers but I won't be messing about with mine!

Cheers

Louise

[Thalestris24]

I guess it's pink because the camera still thinks there's a CFA over the sensor and is adjusting accordingly when converting from RAW to JPG. A custom white balance should fix it as you say but you'll still be applying a debayering routine, which I think you want to avoid.

You need to open the RAW file without applying the debayering routine. I use fitswork4 to do this. There's also dcraw that will do if you're happy to use command line.

Yeah, I was thinking that as how else could colour appear? Though there's no green or blue... I could select the appropriate option in DSS which will tell it that it's monochrome.

Will have a quick go in a min to see if there's any difference.

Cheers

Louise

[james_screech]

Amazing how one camera picks up old ladies and the other one doesn't!

It's due to the extra IR/UV sensitivity, they have an optical cloaking device that doesn't work in either IR or UV. 

James

[Thalestris24]

I guess it's pink because the camera still thinks there's a CFA over the sensor and is adjusting accordingly when converting from RAW to JPG. A custom white balance should fix it as you say but you'll still be applying a debayering routine, which I think you want to avoid.

You need to open the RAW file without applying the debayering routine. I use fitswork4 to do this. There's also dcraw that will do if you're happy to use command line.

Hi Russell

I downloaded the fitswork4 and used it to open the raw file but the output was rather dark?? Not sure what's going on - can adjust it but then it's not a very good comparison. I suppose I could go back and do the same with the colour image but don't have the time right now. Anyway, here's the unadjusted image from the fitswork4 and the auto-level adjusted version:

Cheers

Louise

[Thalestris24]

Ok, these are the colour images loaded via fitswork4 - also came out dark? So desaturated and autoadjusted:

and adjusted:

Louise

[Psychobilly]

As it's full spectrum  is there a possibility that you may be getting UV/IR bloat when used with a lens without filters..?

I'm following this with interest as well... Could do with something to put behind the "L's"....

Peter...

[Thalestris24]

As it's full spectrum  is there a possibility that you may be getting UV/IR bloat when used with a lens without filters..?

I'm following this with interest as well... Could do with soemthing to put behind the "L's"....

Peter...

Hi Peter

Yes, probably. It should be ok with a reflector but would definitely need filters with a refractor. Even with a reflector. I suppose one would normally use some sort of filter whether lp, narrowband or whatever.

Cheers

Louise

[Davey-T]

Heh heh

Amazing how one camera picks up old ladies and the other one doesn't! There is a difference though - I'm not sure how much is due to increased red/infra red sensitivity. That plus UV might have contributed to the difference in contrast but I'm fairly sure it's the microlens removal that's the main culprit. It may not matter that much. How it will perform with low light / long exposure is still to be determined. It will never be comparable to a ccd but can excel in terms of resolution. There are people in the diy section that are experimenting with peltier coolers but I won't be messing about with mine!

Cheers

Louise

Hi Louise, I recently purchased a s/hand Geoptek DSLR cool box, just out of interest to see if they worked, which it didn't, mainly because the person in the factory who assembled it decided to do their own thing and ignore the obvious original design and stick a smaller fan inside that didn't fit the original four holes and stuck it at 45 degrees across the peltier and also not completely covering it which meant it actually increased the internal temperature. Having rebuilt it as per original design and gave it a quick try in the daytime it now drops the temp about 5 degrees but more importantly it keeps the camera at a stable temperature, useful for taking darks. Have a couple of large desiccant bags to fit inside, these also fit much better now the internal fan is properly positioned. Just need some clear sky now to try it.

Dave

[Coco]

Where did you bag the 1100 Mono Louise

[Thalestris24]

Where did you bag the 1100 Mono Louise

Hi

From JTW Astronomy - eventually! I had to wait quite a while for it!

[Coco]

Great thanks... congrats

[Thalestris24]

Just a post script: I had to return the camera to JTW as it had a fault. They couldn't fix it and I finally got a refund in March 2015. Gutted really, but that's astro life!

Louise