I've put this in this forum as a tip for newbies (and not so newbies that are a bit slow on the uptake like me ).
The importance of an IR filter when imaging with a webcam. This is probably an extreme example, but those that know reacon that you need to have one when imaging with a ToUcam and an LPI as well.
These two shots were taken with my SAC 4.2 colour planetary webcam in identical conditions and processed using identical settings. The only difference is that for the second shot I used my DSI IR filter, (for those that don't know the history behind this revelation see this thread and this one as well ) and adjusted the exposure and gain. No colour adjustments have been made anywhere along the processing line.
Anyway...I've ordered a new IR filter, but in the meantime it suddenly dawned on me that I already had an IR filter (of sorts) in my DSI. So I popped it into my SAC 4.2, mounted it in the ED80 and shot a couple of avies with it to see if there was much difference.
The images speak for themselves. Even an elcheapo IR filter can make a huge difference.
Last edited by [1ponders]; 16-09-2006 at 02:10 PM.
The first image I took on the 12th through my 76mm 400mm (approx) FL copyscope, no IR filter and I spent quite a while trying to get the colour right and just couldn't do it. (Image cropped to show similar ROI)
The second image was taken today through the ED80. Stacked and size adjusted with a slight gamma and contrast adjustment.
Your right there Andrew. The biggest problem I had though without the filter is preventing the red from bleeding into the green channel. It's a real hair puller that's for sure.
i am real keen to try my ir/uv cut baader on saturn and then without it on the same night.
see if there is a difference.
It is still lurking in the back of my head your thoughts re blue and red being out of whack on jupiter, ie is it bleeding or collimation??? will the ir/uv cut make a difference or make this colour spread worse??? More things to experiment
Wowsers, as the old Inspector would say.
This is something I had always poo-pooed, but with evidence like this how can I now.
You are saying just ToUcams/webcams, and not DSLR's or anything with a CCD/CMOS??
Well done, and as a hair puller you can't be too careful, you didn't have too much to start with as I recall.
The other night I did an Avi of a photo we have in our kitchen. It is in quite a dark corner and required an exposure of 350ms and 50% gain. I repeated the shot again, just now, with similar settings.
With the resultant Avies I processed the IR filtered one in Registax and did a very light gamma and contrast for taste, and then processed the original avi in Registax, opened it in PS and tried to balance it with the most recent one. I've spent about 5 min getting is as close as I could to each other, as I saw it on my laptop. I've only adjusted the one without the IR filter. Both images have been resized to 900 pixels wide.
btw, I cleaned the chip cover since taking the first. There were just a few dust donuts on it
Last edited by [1ponders]; 16-09-2006 at 03:41 PM.
I haven't tried it with the ToUcam but I'm keen now after seeing this. I might even go out on a limb here and suggest a well calibrated IR filter might be a good idea on a modified DSLR , besides if it's good enough for Hutech then it's good enough for me
So looking foward to getting this Jupiter and Saturn with this camera.
Still experimenting. This image is a single 350ms image using the SAC 4.2. I dumped it into PS did an autocolour , quick curves and levels and then saved for web.
Not half bad for a web cam shooting though a photocopier lens at a photo 8 meters away under very poor light conditions. I'm really looking forward to seeing what this camera can do under the less than optimal conditions of planetary imaging with a decent scope
Basically what it's about Asi is; I've been having trouble getting the colour balance right with my SAC 4.2, as you can see by the non-filtered images here and here. The problem appears to be, for my simple mind, the infared "bleeds" into the green channel causing difficulties in balancing colour and reducing image sharpness.
I posed the question here on which is the prefered filter, Baader UltraViolet and Infared blocking filter or an Astronomik Infared only filter. The outcome was inconclusive as it seems selection is based in personal preference. Also the graphs I posted on the second thread link show very little difference between the blocking characteristics of the two types of filters.
Anyway, in the end I decided to go for the Baader filter, as I could find the most information about it in regards to durability and scratch resistance, even though the cutoff profile was similar and the Baader was more expensive.
However after ordering the filter I realized I already had an IR filter that came with my DSI. So I thought I'd put it in the SAC and see if it made a difference. Hence the purpose of this thread. It really did make a difference in my situation. Once I get the UV/IR I will post comparison shots. The real test will come with imaging Saturn and Jupiter during their next apparitions.
It is even worse than that Paul. The Bayer filters on the chip ALL let IR through. How much depends on the manufacturer. That is why the colour washes out. As far as IR is concerned some chip manfacturers even go to great lengths to get superior 'night' vision with IR LED's by having the colour filters transparent to IR.
A simple example is the colour security camaras with built in IR led's that turn on automatically as ambient light level falls. The picture then effectively becomes B&W.
I think that Scott even noticed this with his modded 350D fitted with a 'clear' filter that IR affected all colour channels.
Bert
![[1ponders]'s Avatar](../vbiis/customavatars/avatar45_9.gif){kind=avatar}
![[1ponders] is offline](/vbiis/images/statusicon/user_offline.gif)
). 
The images speak for themselves. Even an elcheapo IR filter can make a huge difference.
, besides if it's good enough for Hutech then it's good enough for me 
