Question on Camera Focus

[TVEngineer77 0]

I have an Arecont 3105DN camera with a Computar 4.5-12.5MM F1.2 lens on it.

 

I have a problem getting the entire shot in focus, particularly around the edges of the shot. I'm wondering if I setup the lens focus wrong somehow. Things look great right in the center but toward the edges it gets blurry.

 

What baffles me is that you'd think that if something was in focus in the center of the screen it would be that way to the edges of the screen, but it appears as if there's a circular blur around the entire edge. Does this have anything to do with the backfocus setup on these cameras?

 

See the attached pic as reference. Any help is appreciated.

 

[Guest]

I have an Arecont 3105DN camera with a Computar 4.5-12.5MM F1.2 lens on it.

 

I have a problem getting the entire shot in focus, particularly around the edges of the shot. I'm wondering if I setup the lens focus wrong somehow. Things look great right in the center but toward the edges it gets blurry.

 

What baffles me is that you'd think that if something was in focus in the center of the screen it would be that way to the edges of the screen, but it appears as if there's a circular blur around the entire edge. Does this have anything to do with the backfocus setup on these cameras?

 

See the attached pic as reference. Any help is appreciated.

 

 

Can you post the model number of the lens?

 

Ilkie

[thewireguys 3]

http://computarganz.com/product_view.cfm?product_id=778

[survtech 0]

http://computarganz.com/product_view.cfm?product_id=778

The OP said the lens is 4.5-12.5. The megapixel lens you posted (H3Z4518CS-MPIR) is a 4.5-13.2mm. Computar makes 4.5-12.5 IR standard lenses (H3Z4512CS-IR or HG3Z4512FCS-IR), but not in megapixel.

 

I believe the focus problem may be caused by using a non-megapixel lens.

 

That camera uses a 1/2" sensor. Be careful with lens selection because many megapixel (and standard) lenses are designed for 1/3" cameras. Computar's selection of 1/2" (and 2/3", which you can also use) megapixel lenses is quite limited; especially varifocal. They make the one listed above (manual iris only), two 4-8mm 1/2" (manual iris and auto iris) and one 12-36mm 2/3" (manual iris).

[rory 0]

What baffles me is that you'd think that if something was in focus in the center of the screen it would be that way to the edges of the screen, but it appears as if there's a circular blur around the entire edge. Does this have anything to do with the backfocus setup on these cameras?

 

With regular CCTV cameras, typically it is greater focus in the center.

I doubt its the backfocus though, probably the lens as mentioned.

[thewireguys 3]

http://computarganz.com/product_view.cfm?product_id=778

The OP said the lens is 4.5-12.5. The megapixel lens you posted (H3Z4518CS-MPIR) is a 4.5-13.2mm. Computar makes 4.5-12.5 IR standard lenses (H3Z4512CS-IR or HG3Z4512FCS-IR), but not in megapixel.

 

I believe the focus problem may be caused by using a non-megapixel lens.

 

That camera uses a 1/2" sensor. Be careful with lens selection because many megapixel (and standard) lenses are designed for 1/3" cameras. Computar's selection of 1/2" (and 2/3", which you can also use) megapixel lenses is quite limited; especially varifocal. They make the one listed above (manual iris only), two 4-8mm 1/2" (manual iris and auto iris) and one 12-36mm 2/3" (manual iris).

 

You are correct...... This is the lens that should be used with 1/2 sensor.

 

This is the one I meant to post.

 

http://computarganz.com/product_view.cfm?product_id=522

[hardwired 0]

 

http://computarganz.com/product_view.cfm?product_id=522

 

That one's not megapixel, either, and it's 1/3".

 

In the Computar, the H3Z4518CS-MPIR 4.5-13.2mm is the one to use.

 

Also, Fujinon makes the DV3.4X3.8SA-1 3.8-13mm lens that's F1.4, gives a little better light gathering than the Computar at F1.8, also the Tamron M12VM412 4-12mm is F1.4.

 

In the 1/3" megapixel format, Tamron has them down to F1.0 now, handy considering the native handicap CMOS megapixel imagers have compared to CCD.

[thewireguys 3]

 

http://computarganz.com/product_view.cfm?product_id=522

 

That one's not megapixel, either, and it's 1/3".

 

In the Computar, the H3Z4518CS-MPIR 4.5-13.2mm is the one to use.

 

Also, Fujinon makes the DV3.4X3.8SA-1 3.8-13mm lens that's F1.4, gives a little better light gathering than the Computar at F1.8, also the Tamron M12VM412 4-12mm is F1.4.

 

In the 1/3" megapixel format, Tamron has them down to F1.0 now, handy considering the native handicap CMOS megapixel imagers have compared to CCD.

 

 

This is the lens that he is using and it is not a MP lens

[hardwired 0]

Sorry, I thought that's what you were recommending..

 

Anyway, he definitely has the wrong lens for that application, and that's why he's seeing this amount of edge-field distortion and lack of resolution.

 

For really detailed LPR type shots, I've found the best results with fixed-focus Fujinon machine vision lenses.... About 4+ times the price of these lenses, though. He should be a lot better off, though, with any of the true megapixel lenses we've mentioned..

[TVEngineer77 0]

thanks for the help gang, much appreciated. Will look into a different lens setup.

[TVEngineer77 0]

one more question, it was mentioned that I can use a 2/3" lens with this 1/2" CMOS Camera... are there any negatives doing that such as picture crop or (?)

[survtech 0]

Not really. You can almost always use a lens made for a larger imager on a smaller imager, just not the other way around. The image would not fill the screen, like tunnelvision. The only minor downside is that it is harder to find wide angle lenses for the larger imagers. You can find standard (not megapixel) lenses for 1/3" cameras down to 1.6mm or so. It's rare to see 2/3" lenses lower than 8mm. A 2mm lens on a 1/3" camera would give the same field-of-view as a 2.6mm lens on a 1/2" camera or a 3.6mm lens on a 2/3" camera.

 

You do have to watch out for lens mounting types, though - "C" mount and "CS" mount lenses are not interchangeable. You can use a C mount lens on a CS mount camera with a 5mm spacer (C-to-CS adapter) but you can't use a CS mount lens on a C mount camera.

 

 

Most modern analog cameras are CS mount and megapixel cameras tend to be C mount.

[misha 0]

Hi

 

Did you get any better results?