Eytracker Lab - Advice !!

[Peri Trigkas]

grrr its EYETRACKER!!

I don't know if this one fits here or anywhere else in the forum but... I 'll ask!!

We have an eyetracker, which does what it says ...tracks the eye

It uses an infrared camera and the company has provided it with a Canon Lens 135mm.
I have 2 questions!

1. There are some vibration in the room we have the cam (it's mounted on a tripod). We ve been suggested to place the cam closer to the object to reduce the error.. The minimum distance of the lens is something like a meter (not sure I can check though). If we bring the camera closer using a 18-55mm lens for instance, the jumps caused by the vibrations will show smaller? I mean in absolute units. I dont know if I explain it correct.

I'll try to explain in another way just in case. Say u have the cam in 1m distance and focus on the eye with a 135mm lens. Everytime a vibration occurs the cam moves , say10mm from the focused point. If I use a 18-55mm and place the cam at 0.5m the error from the vibration will be again 10mm , smaller, or even bigger?

I know that the more you zoom the more difficult is to keep it steady. I am a bit confused though because in this case 2 parameters change. The focal length and the distance. Im sure that there is someone who is ..more than expert to explain it to me !!

2. Are all lenses suitable for infrared?

Whoever helps, gets credits in my thesis
Thanks in advance.

 

[Hamish Gill]

I've had a drink, and I'm not very tech savvy ... But ...
when I used to sell lenses including binoculars we use to talk about magnification.
10x vs 8x mag ... 8x mag bins will give a steadier image. 10x obviously more mag but would give a more wobbly image. Get closer with 8x and the frame can be filled to the same degree as a 10x pair but with less vibration.
We used to say to people, 10x mag is 10x vibration, same goes for 8 ......

basically, get closer, reduce magnification an you will reduce wobble and therefore reduce error.... Right??

I really hope my brain is in gear here

as for lenses and IR ... I imagine some are better than others as lens coatings are designed to cut certain light etc ...

 

[Adam Lewis]

Peri, I don't know a lot about IR however don't forget on DSLR's there's more often than not, an IR filter infront of the sensor, so even if you get an IR lens or even one of the screw on IR lens bits, a lot of the IR light will get cut by the sensor filter...

I know that doesn't help, and is counter-productive, but there we are.
Btw, I'm assuming you use a DSLR, I have no clue really.

 

[Brian Moore]

I've had a drink aslo and I want to be named in the theesis.

I argee wi' Hamish. hic.

 

[Peri Trigkas]

Peri, I don't know a lot about IR however don't forget on DSLR's there's more often than not, an IR filter infront of the sensor, so even if you get an IR lens or even one of the screw on IR lens bits, a lot of the IR light will get cut by the sensor filter...

I know that doesn't help, and is counter-productive, but there we are.
Btw, I'm assuming you use a DSLR, I have no clue really.

Baically, it's not a camera, looks like a tube actually, that you can mount a lens on it by using an adaptor. I guess it has a sensor able to capture IR without any losses. The thing is that the seller doesnt provide much info. When we asked info about the lens and what we can do to reduce the error he replied that the camera should be used as it was sold to us, meaning with the 135mm canon lens. They don't want to take any other responsibility obviously.

Thanks for your reply though. It helps. The more info I have the better

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I've had a drink, and I'm not very tech savvy ... But ...
when I used to sell lenses including binoculars we use to talk about magnification.
10x vs 8x mag ... 8x mag bins will give a steadier image. 10x obviously more mag but would give a more wobbly image. Get closer with 8x and the frame can be filled to the same degree as a 10x pair but with less vibration.
We used to say to people, 10x mag is 10x vibration, same goes for 8 ......

basically, get closer, reduce magnification an you will reduce wobble and therefore reduce error.... Right??

I really hope my brain is in gear here

as for lenses and IR ... I imagine some are better than others as lens coatings are designed to cut certain light etc ...

Thanks for this. I thought the same as I know that the more mag u have the more error you'll get. I just got confused by the change of distance though. You end up with the same frame by changing the distance and the mag so I thought it might be something that I'm missing.

..but at the end of the day.. more mag - more error.! cool!
Thanks!

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I've had a drink aslo and I want to be named in the theesis.

I argee wi' Hamish. hic.

LOOOOOOOL

I shouldn't be reading this at work...

bottoms up!!