The issue with a pinhole in this particular case is we need a very wide field of view and that is the weak point of pinholes.
The closer the film plane (or sensor) is to the aperture, the wider we can push the FOV, but that creates more light fall-off at the edges of the film/sensor plane which is not ideal for this use.
We can’t add more light inside the machine in order to bring up the edges of the image, without blowing out the detail near the center of the frame. You can’t make the pinhole larger to increase the amount of light coming in, without dramatically decreasing image focus.
Yes the resolution will be a lot less in the corners than the middle. I.e. the camera pixels will represent a bigger area in the bed and a bigger area on the screen when it is de-warped. That will be seen as blurring, even if the original image isn’t.
Even loctite blue is likely to be stronger than the plastic it’s holding.
Loctite red is effectively permanent, as the heat required to denature it will destroy the camera.
Dewarp calibration occurs at the factory for each unit separately. The variation is small but even a fraction of a millimeter is enough to change the position of the alignment on the material.
What they could do is adjust the LED brightness in the case during focus procedure to cover the full range. I believe that’s exactly what many cellphone cameras do with their flashes and you see the flash going off multiple times for a single shot… also, for HDR shots.
Cell phones do that to help their autofocus work, and it’s also red eye reduction - that flash causes subjects pupils to constrict so there is less chance of red eye in the photo, and it produces sharp contrasty shadows which helps the auto-focus lock. They snagged that trick from camera manufacturers.
HDR I’m sure you know is in fact multiple individual shots at different exposures that then get put together either manually or within software. Since it’s cloud based this might take considerably longer to process.
All that said, pinholes are extremely fussy to design and get fantastic results from. It’s much more flexible to use lensed cameras.
Why do people still see large errors when scanning a grid and engraving it over the top of itself? I would have thought de-warp calibration involved scanning a known grid and making sure the intersections were mapped to where they are known to be and everything in between interpolated. Why doesn’t that give near perfect results?
So now I wonder if I ought to expect to be able to place graphics with much accuracy at all. That doesn’t seem to be the case for me with my unit. Is that expected, or should I report it?
To be clear, the cuts and engraving are precise relative to their own features but typically when I place designs in the interface and then cut them, they’re off from where it looks as though they ought to be in the interface, and this error is different in different parts of the bed.
It hasn’t really bothered me, except that I can’t try to use material terribly close to the edge of a piece, for instance, and I’ve got zero confidence in being able to place a feature accurately on something that’s already-made, like say putting a design dead in the center of a phone case or something.
The more I describe this, the more it seems like the problem @Tom_A describes at the start of this thread.
What do you think? report?
Report it!
Be aware though that entering the exact thickness is very important to this process. This is automatic for but you need good digital calipers for other things.
This is one of the features they noted is still in improvement during the “Do you want your Glowforge now?” process. You can report it if you like, but they’re already working on it.
Yeah, I’ve got several sets of HF cheapies that I use for woodworking that I’ve been using which seem to do alright. But if I really need an excuse to pony up for the Mitutoyo… ;D
You’re right! that’s the behavior I’m seeing. I had forgotten in my excitement (yes that’s a laser pun) that it’s already a known issue. Thanks!
Here are a couple ideas of things they could do to improve things:
Dynamic calibration: Using low power engrave, make some marks on the masking surface. Use the lid camera to read where the marks were made and thus use this to fine tune calibration based on the exact height and positioning of the material
Zoom feature: Place your design overall. Select an area where you want to have critical alignment. Use the head camera to scan the area and allow the user to adjust placement within this zoomed-in, highly accurate scan.
Use the lid camera to identify features such as the QR code, edges of the material, other significant features like grid lines. Then use the head camera to look at the locations where the lid camera has identified them to be, and scan them to find their precise locations. Then update the lid scan based on where the head camera found those things.
Not sure we’re having the same problem. I have absolutely dropped objects onto the edge of material and I’ve had no problem adding something to something that I’ve already made.
I have just posted a procedure that lets me get closer with object placement, in the Glowforge Tips & Tricks category: A way to improve object placement
Hopefully that will help until precise positioning is available.
but you need good digital calipers for other things.
