Lightburn Camera Selection 85 or 120

[Phantomzzz (Zach Hill)]

Hi,

I just recently purchased (awaiting delivery) an Omtech Pronto 75 with a 1600mm x 1000mm bed which I’m told by Omtech has a lid open height of 1330mm, I’m trying to decide which 8mp Lightburn camera to get, the 85 degree FOV camera needs a 1384mm mounting height for that size bed, the 120 degree FOV camera only needs 700 and something millimeters mounting height.

Am I better to get the 85 degree or the 120 degree camera?

[Aaron.F (Aaron)]

@Phantomzzz

lid open height of 1330mm,

What do they consider “lid open height”?

The important part is the mounting height from the bed to the camera. See here

With the lid open, you mount the camera where it is roughly in the middle of the workarea, pointing straight down.

On this machine, that would be about here:

I’m leaning towards the 120 degree camera.

Here’s a screenshot of LightBurn’s “Help > Camera Selection Helper”:

[bernd.dk (Bernd)]

@Aaron.F

With the lid open, you mount the camera where it is roughly in the middle of the workarea, pointing straight down.

That is the ideal case you describe. In practice, the mounting height on the inside of the lid is problematic. When the lid is closed, the laser head will not have enough space to be free from the camera. I have solved the problem with my K40 by drilling a hole in the lid and mounting the camera from the outside. However, it is not a nice solution.
With my 600x400 OMT, I have mounted my LB camera on the inside of the lid by the handle, here it is just clear of being hit by the laser head. This creates a non-90 degree angle to the machine bed on the Y axis, but not large enough that the error cannot be compensated for with lens calibration. My retrieval accuracy is significantly below 0.5 mm on the entire bed, even though the camera mounting point is not perfect.
Whether the somewhat larger machine bed gives greater misalignment, I dare not say.

[Aaron.F (Aaron)]

@bernd.dk

When the lid is closed, the laser head will not have enough space to be free from the camera.

Oh, that’s an important part to make sure!

@bernd.dk

Whether the somewhat larger machine bed gives greater misalignment, I dare not say.

The maximum possible accuracy is directly related to the size of the working area and the resolution.
In this case: 8 megapixels (≈ 3840 × 2160 pixels), spread across a workarea of 1600 x 1000mm

@Aaron.F

A typical 8-megapixel camera with an aspect ratio of 16:9 has, for example, 3840 × 2160 pixels.

If your working area is 500 mm wide, this corresponds to 3840 pixels / 500 mm → 0.13 mm per pixel.

In addition, lens calibration (distortion correction and perspective change) alters the image to such an extent that especially at the edges, where the lens is more distorted, two pixels can easily become one.

A precision of “only” +/- 0.2 mm is therefore well within the range.

For maximum precision, it is important to install the camera above the center of the work area so that as little distortion as possible is required.

[bernd.dk (Bernd)]

Thanks Aaron, that’s interesting and useful info. It also covers the relatively low resolution from my replaced LB camera, 85 degrees at 4 mp, that’s right on the border of a necessary resolution.