hi,

I have been reading up on IR filters for a while now, I know of the main applications commonly used here. I am under the impression that the “negative film” or “floppy disk” filter produces less than ideal results and “proper bandpass filters” are the best choice but are quite costly.

I think I have found a filter that exists somewhere in between these two extremes, basically looking for comments/suggestions from you guys:

The IR filter is a 4x4 inch, polyester filter for use in photographic lighting: ‘Gel Snap Holders’

According to the company “Light Transmission begins above 740 nanometers for the 87 model”

At $27 for 100 x 100mm sheet this may be a good buy or am I missing something?

here’s an image of the wavelength characteristics of the various ‘models’ available:

EDIT: Sorry Moderators, I just realised that this is in the wrong section, my bad

Hey this looks promising. Although for a person with only one PS3 camera to mod, this is still more expensive than a bandpass filter. Someone needs to buy these sheets and cut them up into PS3 cam sized squares and sell them (peau?)

Does the company sell single sheets? Is this something sold at a standard camera store or is this a specialty product made only by the one company(I can’t imagine this would be the case)?

Do you wanna tell us what company makes it/where we can get it, so maybe someone can try it out?

jf

Edit: Google search gives us this: http://www.freestylephoto.biz/5331006-Lee-4x4-Filter-for-Gel-Snap-Infrared-87-100x100mm-Opaque

Someone buy one. I would if I didn’t just buy a BP filter.

hey jonferran

Not sure that these are sold at standard camera stores or not but they are surely pretty widely used by photographers, several companies make these gels such as kodak for example but these are the cheapest I have come across,

I didn’t post the link (the one you found actually) as I was unsure of the forum rules on posting links, but I guess it’s acceptable then,

I have ordered a sheet of the 87, will post back when it arrives,

It would be great if the forum could have some more info on this type of high pass filter, I would provide the info but my application is not multitouch at present, it will be motion tracking of dance performers, so my information may not be as usefull to you guys.

So, I will be offering some of this to nuigroup forum users for free, provided that the tests results are posted for others to benifit from the result,

I will be posting my results, even though the application is slightly different.

even

Based on a (very) quick look, these seem to be based on the wratten series (88a, 87c etc.). They are great filters but if i remember correctly they are longpass and not bandpass filters. A longpass will get rid of the visible light but you will still be bothered by alot of infrared radiation coming from many sources around you. A bandpass filter is better for this type of application and you can find decent->good ones for ~20$ at omegabob on ebay. This being said please experiment with what you found, maybe between all these models we will find the ideal one for our needs

madian,

yes they are almost identical to the kodak wratten 87 filter in performance, but way cheaper. As you suggest they are a Longpass filter, allowing all light above approximately 740nm to pass. From what I understand the DIY filters using floppy disks and pieces of exposed film work as a Longpass filter also, although less efficiently, and have been used to some success. I don’t completely understand why a bandpass filter would be better than a longpass filter, unless the daylight levels are high in the surrounding area that is or am i missing something?

even

For a cheap solution it seems good.

The reason bandpass is better is because you only want to see the light that the hardware is producing. Therefore you ideally want to remove any ambient IR caused by other lightsources (lights, the sun, projector, etc). Therefore, a bandpass filter almost always works better than a longpass.

cerupcat,

ok, got it. i’m in a slightly different mindset as I am using the ps3 eye cam in a different situation from most of you guys: i am working in a completely blacked out room with ir lights filling a performance space so I can track motion of people within the space. I should have no ambient light to interfere so I believe this filter should work well for me. 

madian:
would you be prepared to run some spectral analysis on this filter if I send it to you when it arrives?
I have seen your spectral analyses of the other types of filters used here and it is truely a great resource.

thanks guys

even

@even

Sure I will I will test any filter/laser/LED you or other members in the forum can send me. I can work with a 1.5 * 1.5 cm piece or even as small as 1 square cm. PM me when you want to send it to give you the postal info.

@madian

will do, ordered it a few days ago, hopefully it should arrive shortly, i’ll pm you as soon as I get it, I take it this stuff should be handled with gloves to avoid greasy finger marks so I will do my best not to dirty it,

thanks,

even

madian,

I have received the filter, although I have yet to use it. Are you still interested in performing some spectral analysis? if so can you pm me your address and I will post you some to test, regards, even

evengrravy… hi!

can this sheet be placed over the upper layer (just right under fingers touch)? Just to cut any enviromental light which is less 740nm (for model 87).
I think if this is a good enviromental light filter, our tracking system (webcam) can track more easily blobs on surface. (pls say yes that this can be done! - pray)

Hi.... For your consideration:

• $68 - 850 nm Band Pass optical filter for web cam modification—http://www.batteryjunction.com/pl-ir-filter.html

Not exactly “Cheap” but not pricey like a camera lense filter either......

@papakion

You could put this under your touch surface but then how would you see the image through it?? This filters all visible light. Only lets IR through.

With an LCD you could potentially put it below the backlight, or you could just put it in your camera.

Thnx Jonferran...I maybe misunderstand it . Now its clear to me

I just got my Lee Filter 87 and very happy with it.  Much cheaper than those band pass glass filters, but just as effective!

@even

PM sent