Recent content by 336v

Yes, I hear you, that's why I used real 2.7V LDO regulators, not forward biased diode. As of EV error, I must say two well calibrated meters may easily differ by this amount - highly dependent on how you point the meter to the subject, spectra of light (if sight sensors are made with different...

This will not be feasible since the top of the adapter surface will have to be output at 1.35V while inner walls of the same metal chunk are at 1.5V input voltage. E.g. the top of the cell you're using will have to be isolated from the top of the complete adapter solution, so a solid metal...

Two comments on this: - I never thought of adapting a single alkaline or silver oxide cell (1.55V at best) to a 1.35V power source, as you've noticed this leaves virtually no room for the dropout. Such a setup might work initially, but as soon as the source voltage drops to 1.4V, this will stop...

Do you mean a replacement for a single PX625 mercury cell (size wise) for any cameras or photo equipment that was designed to use just one of those cells? It is not difficult to resize (shorten) the side link with regulator ship to make the stack one cell tall (not two stacked cells tall), but...

I've recently gotten a couple of Luna Pro light meters and learned about the issue powering them. Being an EE I've [of course...] decided to design and make a proper battery adapter supplying 2.7V from a lithium battery replacing stack of two original PX625 mercury cells. Not a diode voltage...

I was working on my second Luna Pro meter and discovered that evidently not only appearance had changed over years of production, but actual internal design. From the outside you can see that Some Luna Pro's have ISO speed scale implemented only as ASA numbers, while other models also have...

While repairing old Luna Pro light meter I've noticed that the 6EV filter that gets inserted in the light path for high scale is flaking off - its surface looks like tiny droplets of some substance etched away filtering material leaving dirty spots on filter's glass. IPA does not clean it...

Sure. This is actually wrong forum to discuss embedded electronics but briefly - any microcontroller based project will require some level of programming and I'm not a programmer (and no plans to become one) even if PWM is primitive. Then I'll have to build a driver for the power LED a dev. I...

Good ideas Bill, thanks. I was thinking of LED current regulation for just final fine adjustments to dial desired illumination to get particular EV exposures. Rough illumination without changing color temp would be pure mechanical - I would make crude miniature version of window blinds - you can...

Still planning to calibrate both of my Luna Pro meters with as simple (to me) means as possible. I think I know what to do, just need confirmation I don't miss anything obvious... A search for DIY light box yielded few treads from a few years ago, but people talk about importance of the right...

"Blinded" CdS cell recovers within 5-6 seconds. Under normal (not very rush photography) circumstances this makes no practical difference. It'll take longer to compose a good shot...

Sure, true statement for conventional cameras with lenses. For pinhole photography application it's actually twice as easy: - since the aperture is not variable and always the same for a given camera, you only need the light meter to show you EV number to determine a single parameter - the...

Would be nice, but no need. Luna Pro goes down to f/90, but I always measure for F/22 and then it's just one multiplier, which is square of the ration of my f/319 pinhole over f/22, which happens to be a fixed number 210. So I made a small table in excel for all required exposures corresponding...