It’s a simple fix as I stated earlier: using percentage in this case is a misnomer. It’s using a percentile. Which is why I said it’s misleading. Completely innocently I’m certain as most people don’t know the difference.
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It’s not even a percentile. It’s a number that maps monotonically to power, but we don’t know the mapping.
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Let’s look at another view on this: 3D engraving.
Assuming an 8-bit grey scale, ideally 255 (white) means no engrave. 0 (black) is the deepest portion of the engraving. If I design a slope with a linear gradation from 255 - 0, given correct settings for the material, I want a linear ramp of the engraving from none to deep. If the max depth is 1/4" and I have that linear gradient over a 1/4" width, that should be a 45 degree slope.
If I have two materials that are completely dialed in, one being very easy to engrave and another being more difficult, that shouldn’t matter. The calibration curves per material will see to it that each 1/255 step in pixel value translates to 1/255th of the maximum depth. Maybe one only uses at most 50% power, and the other goes to 100% and uses a slower engraving speed.
This could be a combination of power and engrave speed…as a user I don’t want to have to compute my own gamma curve and process the greyscale differently per material or Pro vs. Basic. Moreover, I can’t control speed with the depth map. But their software, knowing the calibration of the machine and of the material, CAN adjust all parameters dynamically.
They may not have this completely solved, and I may be suggesting more than they are planning, but to my mind, this is how the system should work. The end user shouldn’t have to care what the actual power settings are.
Being able to access the power settings directly might be a fine Power User feature (pun intended), but my understanding is the want to prioritize for ease of use and injecting a bit of Magic on the way–as in “Any sufficiently advanced technology is indistinguishable from magic.” --Asimov
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If you only have 256 power levels then the only way you can get 256 depths is with a 1:1 straight line mapping. If you apply a gamma curve to get a linear output you need more input values to be able to get all possible outputs.
I don’t know if GF are planning to create gamma curves for all the PG materials. I think it is more likely they will map power 1:1 and expect the user to adjust their source image. And how would non PG be managed? Enter a gamma curve in the GUI or simply apply it yourself to your image first.
The other variable is focus depth and multiple passes.
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I did not say that their resolution of power settings are 8-bit. That is a common depth for source bit maps.
If they have even 9 or 10 bits of power control, they can gamma correct.
As for other materials, they have the high res camera on the head. They could run a series of test burns to characterize a material, creating the calibration curves in an automated fashion.
As you point out, there are other parameters that they can combine to get desired effects.
It’s a bit like the transition from a pilot having direct control of prop speed (controlled by prop pitch), power (controlled by throttle), and temperature (controlled by both mixture and cowl flaps) to Fadec (Full Authority Digital Engine Control) where the pilot uses a single lever to call for an amount of power and the computer adjusting everything to best supply the request.
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When asked the number of power levels:
Regarding using the head camera see this post: Accurate pocketing? - #49 by dan
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Bringing sexy back, I figured I’d just toss in my COMPLETE AGREEMENT on this. Changes made now that we’re in production NEED to be explained to the users in a level of detail that will allow the layperson to know how said changes will directly affect them. (In other words, you can’t just say “Various bug fixes.”)
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As I said, I don’t know how much they are biting off. As to 8-bit resolution: as we’ve discussed, there are more parameters than just power. One can reasonably get at least two bits of effective resolution from speed.
My point was not about what GF will do, but why the percentile vs wattage question is the wrong question for many people–and I believe that the best user interface is one where you describe to the glowforge what you want it to do, and it magically does that.
We are not there yet, but it seems we are heading in the right direction.
I would rather have a machine that does what I tell it to do rather than try to perform magic.
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AFAIK, the 256 power levels will be on a sliding scale based around the current % you have set the power level to. So, doing a grayscale engrave at 1% will look drastically different than at 100%
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Not trying to be a jerk here, but then why did you buy a fairly automagical laser cutter?
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How will it do a greyscale at 1%, that implies it can get do 256 levels of 0.4W? I don’t think it can even get near to 1% of 40W before the tube stops lasing.
Because I thought it could make 3D structures with 1000 DPI resolution in XY and Z and I thought I would get in in Dec 15.
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Well the last part, you and the other 9999 purchasers…
As to the first part, I am also excited about that (and I hope the beta users are getting to play with that so far?) but that seems like an automagical feature, rather than a manual control feature. I’m not saying it’s not an awesome feature when it arrives, just you seem to be implying you want more control than the GF ever seemed to imply you’d get.
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I only want to be able to set the speed, power, focus and air assist like any other laser. Happy that it can set it for me for Proofgrade materials but I want the option for manual control.
@johnse wants FADLC, which is think is only possible with some form of feedback. I originally thought that is what the head camera did but it only measures the raw material in one spot at the moment.
Great if it can do accurate 3D engraving with no input from me but I don’t think it ever will. So I think it will be a matter of making my own gamma tables using a micrometer.
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Im not exactly sure how they distribute power in grayscale engrave mode. This is something I have asked about, but havent gotten an answer on yet. Im guessing at 1% the lowest power level is 1% and it scales up from there. Similarly at 100%, the highest power level will be 100% and lowest will be somewhere between.
It would probably take a few test engraves to get an idea of how this works, but I havent taken the time to run 10 or so of the same grayscale, because theyve mentioned the output scale is going to change dramatically once the lower power support comes in, so I am waiting on that to spend the materials to know.
I also do not know what range of power the 256 levels represent. Is it 10% of the total range, 50%, or more? Im not sure.
I do know that the last time I checked, running a grayscale at 1% definitely had different output than 100%.
I also do not know the minimum output power of the tube. I know that laser tubes in the 100W+ range have a hard time doing engraves because their minimum output power is higher than the top end of a 45w machine. (I could be wrong on this. Its hard to find information on).
Either way, id still prefer the 1-100% power choice than having to type in and deal with wattages. Its just easier to remember. The output wattage of laser tubes vary over their lifetimes anyways, so it wouldnt ever be spot on accurate.
Im hoping at some point they can give us some schooling on output power and scaling, and how grayscale engraving fits into that power range. The more understanding of this I have, the better I will be at utilizing this machine to its full potential.
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3D engraving is great and fun, and was one of the main features I purchased the laser for. Ive been doing it manually since I got the laser, its no different than a regular engrave, you just bump up the power and slow the speed so it ablates more material. Additional passes help increase the depth, but lower overall quality of smooth areas.
Getting a specific depth via 3d engraving is going to take a lot of trial and error with every material. So far for me its just been the fact that I can get enough difference in depth to distinguish whatever im doing as a 3d engraving. The soot buildup on wood helps a lot in that as it darkens deeper areas more. So far it seems to me that if you want really accurate 3d engraves with specific depths, a CNC machine is the way to go. Those guarantee the exact depth profile you are looking for. 3D engraving on a laser is more about getting small details onto something than getting everything proportionately accurate to your 3d model.
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Yes exactly. While it is all magic we can’t rationalise about it. The fact you have 1% not equal to 1% of 40W means the minimum power is hidden.
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That part would be a nice to know, but just on the level of understanding CO2 laser tube physics for me. In reality we are stuck in the realm of what that tube will actually output, which we cant change, so a friendlier scale of 1-100 is totally fine with me as long as it really does encompass the full lower spectrum of laser power output (all the way to the point of not firing).
Im hoping they cap the output at the top to prevent anyone from accidentally overdriving their tube and killing it immediately, which im pretty sure theyve done. On my k40 I cant push the dial past 60ish% or it will start to degrade the life of the tube and give me no worthwhile additional power returns.
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@Dan confirmed that a couple of months ago when I posted about my PRU. I didn’t want to use the 100% setting if it was going to push the tube past rated values like the K40 
I was looking for something like the Redsail config file that lets me make 100% in the software equal 95% of rated tube power so I don’t prematurely wear it out (the last 2-3% power causes a hugely disproportionate reduction in tube lifespan) or overdrive it which is even worse. Dan said that 100% in the software is set so it achieves the tube lifespan they’re projecting.
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