Phenom Z-Axis resolution

I have looked all over the Internet for Z-Axis resolution with no results. So I decided to determine the the mechanical resolution is but not sure how this will affect resolution. The lead screw in the Phenom has a 4mm pitch when roughly measured. Most stepper motors have 200 steps per/rev which would produce .02 mm/step Z-Axis. The sample Chitubox configuration file (Phenom Deft 50uM 12s.cfg) that comes with the Phenom uses a 50uM (.05mm) Z-Axis step. Is it possible to print using 25uM or even 20 uM step? Is the resin exposure time a linear function, i.e., 25um slice half the exposure time of 50um? I am very new to 3D printing, looking to print small high definition parts. 50um was probably chosen because the xy pixel pitch is 72uM, yes? I realize smaller Z-Axis steps will probably shorten the LCD life.

The stepper motor driver uses microstepping to subdivide the 200 steps. The product page of the moai claims that 5µm layer height is possible mechanically. So i guess the mechanical limit for the Phenom would be the same.

The main limitiation in SLA regarding layer height is that all laser light has to be absorbed inside the layer, otherwise negative details get washed out. Because of this all SLA resins contain light blockers (fluorecent compounds) that absorb laser light and convert it to a higher wavelength to limit the cure depth. 20µm layer height is possible but negative details maybe get washed out because the resin can’t absorb all the laser light inside the layer thickness.
Cure depth is a logarithmic function of the exposure time, in classic laser based SLA. The graph below is for the acrylate resin XB 5081-1 from 3D-Systems:

The resins for MSLA are a bit different, so maybe take a look at the 100µm profile of the Phenom?

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Thanx for info. Since the MSLA uses an IR array at the same wavelength, the curing effect would be the same. I am trying to create a mechanical part with high def threads. Thinking about possibly replacing the UHD 12.5 in LCD with a 5.5 in UHD LCD to improve the pixel pitch (by min of 2x) this is why I was concerned about 20uM Z-axis resolution.

interesting topic, @Russ the mechanical accuracy of the z-axis is generally much higher that what resin able to express.
A section of our resin guide talks about the consideration for layer height.
in short, print 40-60um and don’t go above or lower for current generation MSLA printers

the details is in resin guide found on wiki