IR Filter comparison test - Results

[ballaratdragons]

I had a beautiful night for this comparison test of my new IR Filter test.

The sky cleared up to give 8/10 seeing and 10/10 Transparency.

The below images of Carina Neb and Keyhole are taken under almost identical conditions, seeing temp etc.

All images taken with ED80, modified Toucam 840k Pro II, Focal Reducer, stacked in Registax, all processed equally in PhotoShop CS.

Make up your own mind about the results, but as usual feel free to comment or help.

IMAGE 1:
In the 1st panel is Carina with no filters at all. Just raw Toucam.
In the 2nd Panel I used the crummy little Toucam Lens IR Filter.
In the 3rd panel I used a proper Astronomical Imaging IR Cut Filter.

IMAGE 2: The full size images cropped to show real-size detail.

[ballaratdragons]

Here is the same test done with Trifid nebula.

All have equal processing and almost similiar imaging conditions.

[ballaratdragons]

And same with NGC4945:

[davidpretorius]

i am not sure Ken, different details. not sure which one i prefer??

great to see you have some lovely nights

[joe_smith]

the IR cut filtter has made the stars look heaps better, they look more sharper and smaller/less bloat (if you know what I mean) to me. But I dont like the lost color can you get it back to red somehow?? then it would rock. I cant believe you are getting these with a simple webcam you are the man, well done mate :thumbsup:

[joe_smith]

forgot to add the IR cut filter one look likes it got less noise as well.

[mill]

To me the toucam filter looks best in all these pics.

[jase]

Ken,
Do you know the characteristics of these IR filters? Undoubtedly, the have different transmission and IR wavelength characteristics. I prefer the Astronomical IR filter as it really does cut down star bloating (as Joe mentioned), however this can be remedied in processing techniques - its still best to prevent it occuring in the first place.
IR filters could start at anywhere between 659nm through to 800nm, hence its difficult to make direct comparions. In addition to this they all are likely to have different transmission characteristics ranging from 60% to 95%. If your Astronomical IR filter doesnt have a good transmission rate, then you're going to need to increase exposure time to compensate - this *could* partly be the problem why the colours are off with the Astronomical filter. Finally, you need to also consider spectral response of the Toucam. Its will not be 100% over all visual wavelengths thats for sure.

[ballaratdragons]

Jase,

if I take longer exposures than these, the Amp Glow dominates the image. I did take an image only 30 seconds longer and 3/4 of the image was washed out and lost to Amp Glow.

So, unfortunately I don't have the luxury of longer exposures than 180 seconds, without getting the 'Amp Off' mod done.

Joe, less noise in the IR cut filter image was done by me using PhotoShop actions. I forgot to do the other 2. :doh:

To me, the Toucam filter and the IR Cut filter give identical clean stars.

None of the images have been processed to 'nice' level. I usually do quite a bit of processing with them but that would not give a comparison of data collected in this instance. So I left them almost Raw.

[Tamtarn]

Great comparison test Ken

We prefer the crummy little Toucam filter the best :lol:

Both the filters do a great job on star bloat but there's a loss of detail and colour with the IR cut filter. Maybe it would perform differently with a DSLR :shrug:

[erick]

Just checking, Ken. That's the IR cut filter or the IR cut combined with UV cut?

[Garyh]

I say the original Toucam filter for me..
I reckon it gives the best result as the onboard camera processing is designed around having this filter present...
great comparison Ken..
cheers

[ballaratdragons]

Just IR, Eric, not UV.

[ballaratdragons]

I agree. I think the Toucam innards may be different compared to DSLR's.

As Gary says:

[ballaratdragons]

Here is another comparison.

I am still processing from last night. Only Jewelbox and Omega C to go.

But here is Centaurus A comparison.

Top is Toucam Filter, bottom is IR cut filter.

[ballaratdragons]

Here's Omega Centauri compared. Both look OK in this comparison. :shrug:

[ballaratdragons]

and the last one from last nights test.

Jewel Box Cluster.

[joe_smith]

The IR cut filter cuts a lot out they look faded compared to without it.

[ballaratdragons]

Yep Joe, but I suppose that's where longer exposures come into it, which I can't do without the 'Amp Off' mod.

Wierd how it sends EVERYTHING Blue!

[monoxide]

thats strange ken, i wouldnt have expected an IR cut filter to turn the images blue? then again, i guess i have no idea what im doing lol.

[ballaratdragons]

Ditto TJ.

[h0ughy]

curious Ken, what is the better result for you, with or without?

[ballaratdragons]

Houghy, I find the stars in the IR Cut images just a tad sharper than the Toucam filter images, but not by much.

The 'No Filter' images really have stunning nebula, but horrid stars, so I'd say I'd go with the little Toucam Filter. It would be nice if I could get the natural colours (or any colours!) with the IR filter. Maybe there's something I'm doing wrong, or the Toucam filter is balanced to the Toucam chip :shrug:

[ballaratdragons]

I just had a thought!!!! (I know, hard for me :lol: ),

Maybe IR filters are only meant to be used on Monochrome Chips!

Correct me if I am wrong :shrug:

Image 1. Toucam Filter converted to Greyscale

Image 2. IR Cut Filter converted to Greyscale

They look identical to me! The Toucam Filter is slightly brighter in the nebula, but the stars are the same.

[monoxide]

i just edited all your pics to greyscale and was about to post the same thing lol

[ballaratdragons]

:rofl:

It pays to Google!!!!! :eyepop:

Look what I just found on a site about using IR filters with CCD chips:

Is there such a thing as a Color IR Filter? No. Visible light goes from violet at 350nm to red at 780nm. Color doesn't exist for humans or the camera in IR which is over 780nm. The camera only sees Black & White in the IR region. The closest thing to color is some of the $10,000 heat sensitive, cooled cameras which re-map the IR information into the color range.


And this statement (except in my case it's BLUE):

How come my camera shows a green picture if IR is Black & White? Because Sony thinks it looks better. Green is in the middle of the color range.

:screwy:

[monoxide]

i dont see how though, isnt the idea of the IR cut filter to block IR and let everything else through normally?
if you hold the filter up to a light does it look blue? if not then its something funky with the toucam

[ballaratdragons]

Everything looks the same colour through the IR filter, lights, daylight etc.

But the little Toucam one is a light yellow colour so It must be matched perfectly to the chip.

And if the experts say the IR filter won't show colour, then they must be right.

Further reading on the net has just told me that Sony Chips are 'Near Infra-Red'. not full Infra-Red. Must make a difference.