electronics – Koraks tinkers

Fade to black – Why ‘modern’ Gossen light meters might drain their batteries

This came up the other day on Photrio where @RalphLambrecht wondered about why his Gossen light meters drain their batteries while they’re supposed to power down automatically. Now, I happen to have one of those Gossen meters powered by a 9V battery, so I figured I could have a peek inside to see what might be wrong with his.

Cheap chips from China – A brief look at the CH32V003 microcontroller

I admit I love AliExpress specifically for low-end electronics components. I often shop around for stuff like IC’s and microcontrollers. And while you can get certain Microchip (Atmel), Texas Instruments and STM devices attractively from China, this has been starting to feel a bit odd to me. After all – a nation that retrieves rocks from the dark side of the moon is surely capable of making a decent microcontroller by itself. So why purchase Western parts from China, and not dip into the actual Chinese-made (and, in particular, engineered) stuff? So that’s what I did!

Solid as a rock – Fixing an old AC stabilizer

Sometimes, a piece if equipment finds its way to me for repairs. This time, it was an old Devere voltage stabilizer, apparently used in conjunction with a 5108 enlarger. Very nice piece of kit. With one problem – it didn’t work. But I think we got ‘er fixed up again.

Sloppy slopes – Green and blue LEDs for variable contrast black and white

Recently, I wrote about a new RGB LED head for color printing and reported on some step wedge tests I had been doing. The other day I was printing some black & white negatives with this new head, and I ran into some looooong print exposures. This led me to do some additional testing, which yields some interesting (I think) insights.

Trans-mission – A parts bin transmission densitometer

I’ve never owned a transmission densitometer. In fact, I consider myself as far too sloppy and undisciplined in the darkroom to be able to put one to good use – so why bother? Then again, sometimes it’s just convenient to be able to take a few quick and dirty measurements on a piece of film. And there’s always the parts bin full of stuff that surely could be fashioned into a densitometer, right? Right.

Perfecting primaries – Another look at LED wavelengths for RA4 paper

Way back I explored the best wavelengths for exposing RA4 paper. In that blog entry, I pitched an idea of optimal wavelengths that I hadn’t tried yet. Well, I picked up the glove myself and I think the results could be pretty relevant. Read on, especially if you’re looking to purchase or build a LED exposure system for color enlargements.

Shine a little light – A brief note on UV output degradation in LED floodlights

I’ve been using cheap & cheerful UV floodlights to expose my alternative process prints for a little over a year now. Since then, a few people have remarked that there’s a problem with these LED flood lights: their power output reduces as the unit operates due to the LEDs heating up. How bad is the problem, really, and what to do about it?

Big ugly no longer big (still ugly) – RGB LED head for color printing revision

As soon as something sort of works, I generally leave it as is and use it as is. Until the shortcomings become annoying enough to actually do something about it. Which is the story of my color enlarger project in a nutshell. A story that hadn’t see much development lately – after all, it sort of worked, right? Well, the annoyance got the better of me, so I did another iteration.

Kind of blue – A test with UV LEDs for DAS carbon transfer

So the 400nm LEDs I had been using since October or so worked really nice for dichromate carbon transfer, but I ran into trouble with DAS carbon with them. Some further testing with my bank of trusted Philips BL tubes and a little theoretical exercise suggested that at least some 365nm exposure is needed to get DAS carbon to harden reliably especially in the highlights. So I’ve been testing a bit with 365nm LED options – two in particular that seemed attractive. This is a small report on these tests.

Fixing Sekonic L-358 and NP spot meter wrong readings

Years ago I picked up a second-hand Sekonic L-358 and have used it ever since with great pleasure. One of those things you just turn on and it works – provided you feed it a new battery once every few years or so. Recently, I got a 5 degree ‘NP Finder’ for it, which turns this incident light meter into a proper spot meter. However, today I ran into a disconcerting problem: totally wrong meter readings. What’s up with that? And can it be fixed?