welder's glass

[Rhea 0]

Lots of folks here talk about using welder's glass for cam focusing... Looks I need one.. I installed all my cams during day time, and they're all out of focus somehow... have to try focus using that glass.. Is it available in stores?

Thanx

[Soundy 1]

What cameras are they? What lenses are they using?

 

The idea with using welder's glass is to cause the iris to open fully in bright light to reduce depth of focus, but that only applies to auto-iris lenses. You can get around it by disabling the camera's iris-control function (often a switch or OSD option to toggle DC and ESC) - switching the ESC (electronic shutter) opens the lens iris fully. Or try focusing in lower light when the iris opens naturally.

 

You'll also have night focus issues using a non-IR-corrected lens on a true-day/night camera.

 

For welder's glass, you'd have to go to a welding shop, and you don't want anything darker than a #5 (I found some auto shops and tool shops that have the glass, but could never find anything lighter than a #. You can also use a photographic ND (neutral density) filter.

[norcaldad 0]

Not sure what you have in your area, but you might be able to pick them up at an "ag supply store," Tractor Supply, Sears, Orchard Supply and perhaps Harbor Freight. As a welder in a former life, I have glass in my helmet; flip front lens, but all I see anyone using now are the auto-darkening helmets. Perhaps glass will be a thing of the past.

[survtech 0]

The idea with using welder's glass is to cause the iris to open fully in bright light to reduce depth of focus, but that only applies to auto-iris lenses. You can get around it by disabling the camera's iris-control function (often a switch or OSD option to toggle DC and ESC) - switching the ESC (electronic shutter) opens the lens iris fully. Or try focusing in lower light when the iris opens naturally.

Soundy,

 

We occasionally use #5 welder's glass for manual iris lenses too. On many cameras, opening the iris fully will overload the video, making it difficult to focus. The welder's glass allows the same focus functionality with manual iris lenses as it does with auto-iris lenses.

[Soundy 1]

The idea with using welder's glass is to cause the iris to open fully in bright light to reduce depth of focus, but that only applies to auto-iris lenses. You can get around it by disabling the camera's iris-control function (often a switch or OSD option to toggle DC and ESC) - switching the ESC (electronic shutter) opens the lens iris fully. Or try focusing in lower light when the iris opens naturally.

Soundy,

 

We occasionally use #5 welder's glass for manual iris lenses too. On many cameras, opening the iris fully will overload the video, making it difficult to focus. The welder's glass allows the same focus functionality with manual iris lenses as it does with auto-iris lenses.

True, but then, if having the iris full-open overloads the sensor, then that camera will normally be operating with the iris partially closed, no?

[Rhea 0]

The cameras I have installed are these:

 

http://enstercctv.en.alibaba.com/product/538868679-213161793/700_TVL_EFFIO_P_WDR_SECURITY_CAMERA.html

 

http://enstercctv.en.alibaba.com/product/446068864-213161793/Vandalproof_Box_Sony_700_tvl_Camera.html

 

http://enstercctv.en.alibaba.com/product/429478419-213161817/700_TVL_SECURITY_CAMERA_infrared_camera.html

 

Been cooperating with this manufacturer for 3 yrs now... have regular 450 Tv line cams and their DVR in my office & warehouse. Decided to go a bit higher and got Dahua 1U DVR and these cameras. Frankly, even with HDMI input and these cameras I am not that happy, as the difference in picture resolution is not that much striking different... that.s why I think maybe I have to be more precise with focusing. I have been using this to set up the cam video from the same manufacturer :

 

http://enstercctv.en.alibaba.com/product/248831832-213162256/security_monitor_video_camera_tester.html

 

Thanx for help!

[survtech 0]

True, but then, if having the iris full-open overloads the sensor, then that camera will normally be operating with the iris partially closed, no?

True, but if the iris is partially closed, you lose depth of field, or rather, you lose that "edge" to the focus. For many situations, that may be tolerable but in certain applications where focus is super-critical, I've found we can get better results focusing with the iris fully open, then closing the iris until the best overall picture is obtained.

 

Also, in some situations, I find it necessary to close the iris after focusing so that certain details can be seen despite the rest of the picture appearing overly dark. This is true when trying to capture the pay line on slot machines or the cards laid out on a table. While under your average situation, it might be preferable to have an overall pleasing picture, in those situations it is necessary to trade off having some dark areas for clarity in others.

 

By the way, we also commonly turn off the auto-iris function and manually adjust the iris on auto-iris cameras for the same reason.