How does the focal distance affect the image clarity

[florin 0]

My application requires to monitor an area located between 0 - 10 feet from the camera and as wide as possible.

 

I bought a camera board with a 3.6mm lens and after I custom built the enclosure and started the system I noticed the image is not clear at all. I took some measurements and found that my lens is actually 6mm, and not 3.6 as I was told.

 

From what I understand, 6mm is suitable for longer distances, further away, so I am assuming the camera cannot focus right in 0-10 feet because the lens is 6mm instead of 3.6mm. Is that correct? If I replace the 6mm lens with a 3.6 lens, will it be able to focus better in 0-10 feet? Is a 6mm lens supposed to have the same image clarity with a 3.6mm lens at the same distance?

 

Maybe my lens is just not installed right/ focused right? Anyway, it will be a nightmare to open it's enclosure and fix it. I learned the hard way that I have to check it before installing.

[rory 0]

6mm should be clear at 10' (from the camera).

Recheck the lens and make sure it is focused properly.

Are you sure it's not just a crappy camera? What is the model number?

When it is not clear, any specific time of the day/night?

[florin 0]

Rory, thanks for the quick reply.

 

It is a 1/3 " Sony cheap crappy camera, but it is the second crappy camera I used and the first one worked much much better. Here is a movie of the first camera that cost $15 on ebay (it's a 1/4" CMOS 2.8 mm reverse car camera) and worked just fine:

 

The second camera is 1/3" Sony that I was expecting to be better. Here is a movie made with it. It's pretty bad:

The specs of this camera are here, but it's 6mm instead of the advertised 3.6mm: http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=11977

 

Any advice for a more suitable camera board for my project is welcome.

[Soundy 1]

There's no reason the camera shouldn't be able to focus a <10'... just that by default, these cameras are generally pre-focused during assembly to a farther focal point in an attempt to maximize overall DOF. To get into the 0-10' range, you'll need to re-focus it manually. However, you likely won't get that FULL range into focus, even with a shorter lens (although the shorter the lens, the more DOF you do get).

 

The biggest limitation of the 6mm, really, is the narrower field of view.

[rory 0]

Get one of the higher resolution KT&C board cameras instead.

Although you probably just need to focus that one better.

[florin 0]

Thanks for all the answers, I'll try to readjust it first and post againg the results.

 

Awsome forum, lots of things to learn,

Florin

[rory 0]

Take a look at the KT&C ACE-VMN320NHB

If it comes with a fixed IR cut filter placed over the chip (as I suspect it does) you could remove that to gain more sensitivity in low light, though you could loose the real colors especially if the sun is out (no idea about underwater though).

That is 0.5 Lux. The higher resolution does not see as much in low light. But better clarity.

KT&C also sell the fixed lenses individually.

[florin 0]

rory, thanks again for the help. Your mention about removing the IR filter reminded me that I do have another camera that I can use, but it cannot see IR with it. If I can only remove the filter...that would be awsome, as I was very happy with the performance of this camera. Can you instruct me how to remove tat IR filter?

Here is a link to the camera specs: http://www.securitycamera2000.com/products/1%7B47%7D3-SONY-CCD-520TVL-Camera-Board-Lux0.001-High-Resolution.html

 

If the link doesn't work, here are the specs:

TV system NTSC PAL

Image sensor 1/3 inch Sony CCD Image Sensor

Effective pixels PAL: 752 (H) x 582 (V)/ NTSC: 768(H) x 494(V)

CCD total pixels ~ 270K ~ 320K

Sync system Internal

Minimum illumination 0.001Lux F1.2; 3200ºK (20IRE) (Sense UP Max.)

Lens & view angle 3.6mm

Resolution 520 TVL

White balance Mode ATW / AWC

Range 3200 ~ 10000 ºK

S / N ratio typical (MAX ) 50dB (MIN) / 58dB (TYP) (Gamma, Aperture, AGC, OFF)

DNR (Digital Noise Reduce) S/N UP 4.5dB

Gain control AGC ON / OFF

Sense up ON /OFF (Preset X6, Option X32)

H – mirror function OFF / ON

V – mirror function OFF / ON

B.L.C. function ON / OFF

Color bar OFF / ON

Auto IRIS A.E.S. / DC-IRIS

Electronic shutter 1/60~1/120,000 sec. 1/50~1/120,000 sec.

Video output 1.0V p-p composite video at 75 ohm With monitor output

Operation temperature -20℃ TO 50℃

Operational humidity within 85﹪RH

 

I will also check the camera you suggested.

 

Again, thanks for all the help and patience.

Florin

[rory 0]

its the extra piece of square glass that is glued over the chip's glass.

So remove the lens, remove the lens holder, then should be able to get at it.

 

see it clear in this photo, that little aqua color thing on the very top.

[florin 0]

"glass that is glued over the chip's glass"

 

Glued? If I remove that, should I expect some messy glue needed to cleaned up from the sensor? If I have to glue it bak, what kind of glue should I use?

 

I hope I can do it tomorrow night.

Thanks,

Florin

[rory 0]

With the camera I did it to, it was more like some kind of putty, it came off. Otherwise could use Rubbing Alcohol to clean it up, but a really soft cloth like eye glass cleaners. In my case there was no way to access it easily, it was way down into the bullet camera, had to keep picking at it with a small screw driver, eventually I just ended up breaking the glass in pieces (by accident) and picked out the pieces I then used the small eye glass cleaner cloth on the end of the screw driver to push it down into the bullet camera housing and clean up the residue left over, dont recall having to use anything else.

[Soundy 1]

Keep in mind that removing the IR cut filter will make for really weird results in color mode, if the camera isn't designed to compensate electronically (if it were, it probably wouldn't have the filter in the first place).

 

Here's one of Rory's examples from another thread:

[florin 0]

Soundy, thanks for the heads up.

[florin 0]

In the end, I decided not to remove the IR filter (I chickened out).

Before assembling it, I checked the focus and I was able to get a much clear image by turning the lens about 60 degrees counterclockwise. I am soooooo happy with the clarity of this camera.

 

I built the underwater enclosure and tested it 2 days ago when I went ice fishing. Here is the footage (the original footage has better clarity, I lost some quality when editing):

 

Thanks for all the help.

[Soundy 1]

Nice, FISH STICKS! That one pike seems to be kind camera shy around the 2:00 mark, hanging out WAY in the background The one minnow doesn't seem too thrilled with his situation, either.