Macro webcam?

[Roy G. Biv]

It was suggested that I post this question here. I have a webcam pointed at my tank, Its almost as if the picture I get is zoomed in by 4 feet. Meaning if I want to get the shots I want, I need to place the webcam 4 feet away from the tank right into the living room. What specs am I looking for in buying a webcam that will give me a closer focal point. Ultimately I want to attatch it to the hood of the tank. As it is now if I do that, I get a good shot of a 6 inch section of the back wall. I was thinking that laptop webcams are rated differently than desktop ones since laptop users tend to be closer to the screen than desktop users. I just need a little info to get me on my way here.. Thanks.

 

[gregr]

A little explanation on how lenses work: telephoto lenses are the long ones- they help make far away objects appear large in the picture. Wide angle lenses allow you to see a lot of real estate, basically the opposite of telephotos. A fisheye lens is an extremely wide angle lens.
When you had your webcam positioned across the room you needed more of a telephoto type lens, something in the range of 100mm roughly, to isolate just the tank. The lens on the webcam you have is too wide for this (as you found out)-- you had to have the camera much closer to isolate the tank. When you mount the webcam on the hood you need just the opposite because the camera in now super close to the tank... you now need a super wide lens. It'd be nice if you could split the difference but life is never easy...
If I understand you correctly what you need is an extremely wide angle lens on your webcam. Extremely wide-- probably a fisheye (no pun intended...) lens will be the only thing that will get you close to seeing the whole tank when the camera is mounted on the hood. Fisheye lenses are super wide but they also introduce distortion-- curved horizons.
Does this make sense to you?

 

[gregr]

Another issue with the camera mounted on the hood is it will be shooting at quite a downward angle into the tank. Shooting at any angle at all (other than squarely into the tank) intoduces distortion into the shot because of the extra acryllic/glass that the lens is shooting thru. Webcams are pretty poor optically to start with, then add compression... you're going to end up with a very poor picture. It may be ok for your purposes though.
One more clarification-- in regular photography lenses are defined by their focal length. A telephoto is roughly anything from about 150mm on up to the longest they make. Wide angle is generally defined as 35mm or wider. A nice wide angle lens for a regular digital camera (slr style, not point and shoot) is 24mm. Fisheye lenses are generally in the 10-15mm range. To make a lens that wide is very difficult, hence the distortion. Lenses that are very wide and have low distortion are very expensive. This all relates to regular photography but gives you a little background so you know better what to look for in a webcam.

 

[Roy G. Biv]

Thank you. That is very helpful. It gives me an idea what Im looking for now!!

 

[Roy G. Biv]

I did a quick search on ebay.. Below is a description. Is this what you think I am looking for??

Parameters and Features:

Color: black
Connection: USB
Current supply: over the USB connection of the computer
Focus manual: 10mm
CMOS chip type: color CMOS image sensor
Dissolution of fixed image: 640x480, 352x288, 320x240 pixel, 176x144pixel, 160x120pixel.
video dissolution: 640x480 pixel
Video format: 24-bit True Color RGB
Video picture rate: 320 x 240 to 30 frame/second (CIF) 640 x 480 to 15 frame/second (VGA)
2P2G Lens set
Size: approx. 4cm x 3cm x 3cm
Cable length: approx. 120cm

 

[gregr]

It's hard to tell from that description-- "Focus manual: 10mm" is kind of meaningless, at least to me anyways. If that means a 10mm focal based on a regular 35mm frame then yes, but I'm skeptical. Can you find a model number for that camera?

 

[gregr]

The more I look at that description the hinkier it sounds. Dissolution of fixed image? I think that description may suffer from a poor translation from a different language.

 

[Roy G. Biv]

Update... Got everything setup. I bought a cheap webcam..

6 mm lens
Interface: USB, USB 1.1/2.0 compatible
Hi-resolving power: 1280 x 1024 / 1024 x 768 / 800 x 600
Video mode: 24 bit true color
Frame rate: 320 x 240 30F/S 640 x 480 15F/S
Powered by USB port, no external power adapter required
Built-in image compression
Image focus: 5cm to infinity
System required: Win 98/SE/ME/2000/XP
Height: 48 cm
Colour: black

The cam was 10 bux shipped.
Now I know you get what you pay for and this cam generally sucks. The Image I get when it works is exactly what I want, and the snake like body allows me to position it un-obtrusively. The issue is that the video gets choppy, and sometimes doest work.

Now that I know a little of what I am looking for, what kind of framerates do I look for now. The 320 x 240 30F/S that is listed in the specs is what I matched to windows media encoder. Do I need to look at something else for the framerate?