As ray says, a narrower lens would be ideal for this. Using a 170 degree lens from a meter up would be great for filming the whole room, but not great for maximizing the bed of the laser in the captured frame.
Oz - since I believe you and I have similar 700x500 machines, in your experience, what specific lens length is the all around best compromise? 90? 80?
When I open up the lid on my machine and measure from the angled front area of the opened lid (most flat area when lid is raised) down to the bed, it appears I will have in the 600-620 mm range. I have done the calculations on the ordering page and those say I can theoretically use 80 and higher.
I’m not Oz but I sometimes play him on the internet.
General-general all around would probably be the 140.
For “general but more specifically the red and black the 700x500 machine” you can go one or two lens angles smaller because you can mount it at a higher distance up than with a smaller machine.
Will defer to Oz for the official stance though, since he has said larger machines.
Thanks, Ray. Just trying to separate out the theoretical from “real world reality.” Wider view sounds better at first thought but if the wider view produces noticeably less accuracy then maybe it isn’t worth it.
For the red/black, the 140 seems like a good choice for lid mount. It’s got enough extra room to allow some flexibility.
For the red/black 700mm x 500mm, here are the images from 3 different cameras mounted in the lid:
and 120 degree (note this is fuzzy because I didn’t take the sticker off the lens):
The 120 cuts it pretty close, while the 160 captures too much extra around the bed.
Thanks for posting the pictures.
For the red/black, the 140 seems like a good choice for lid mount.<<
So, in real-world usage the 120 lens’ ability to “see the material on the bed a little closer” (for lack of a better term) is not as beneficial as the 140 lens’ added flexibility via its extra angle of coverage, correct? Not trying to beat a dead horse, I just want to make sure I have asked the right questions. Getting confirmation now is easier for both of us compared to ordering a second camera later Thanks.
Correct - the 140 sees a little more, so you have a bit more flexibility with mounting.
So, for a k40, with the stock bed torn out, I could use the 60° lens, yes? (Assuming a lid mount)
Measure and do the math - it’s very easy.
Oz, I’m a firmware engineer… I don’t trust my math
I’ve considered the 140 to be the best general purpose lens size - solid for the K40, and that’s entirely what C3D will be stocking shortly.
I’ve got the red/black 700mm x 500mm and to ask another question, that’s probably been answered elsewhere (sorry if it has), what are the trade offs between the extra flexibility with mounting the 140 camera compared to using the 120.
Is the 140 less accurate, for example. Or are the differences so minimal the 140 would be a better option to go with just for that extra security/flexibility?
The higher you go, the more fisheye distortion you’ll have that you have to compensate for. This is why I try to avoid the 160 almost completely unless you really really need it.
This is a 600x400 bed with the 140 degree camera mounted at the inside top lid area.
The camera is mounted too high up so you have an unclear image of the bed. This person needs to move their camera mount lower to be closer to the bed. To keep their camera at the current position, the math suggests they need a 90 degree lens.
I hope that illustrates how the difference there is more extreme, I would worry less about the difference between a 120 and a 140 in favor of the bigger one that provides more wiggle room.
The pics above in this post really show the same thing I just illustrated.
I’ll do the math when I get home and check distance from lid. I was more concerned about the accuracy but from what has been said I don’t think there’ll be that much difference and the 140 should make it a easier to mount.
The tighter the “fit” to the bed area of the machine, the better. In the image Ray shared above, the user has the bed covering about 50% of the image from the camera. This means fewer camera pixels per mm of bed, which translates directly into placement precision.
With a 2594 wide camera shooting a 600mm bed, the best you’ll get is about 4 pixels of image per mm of bed, so 1/4mm precision is feasible. If you’re using half the camera image, you get half the precision, but it’s still pretty good. It’s more important to have a tighter fit if you have a large machine and still want high precision.
Thanks @LightBurn great response