Using grains focuser with or without paper on the easel

[Sirius Glass]

The left hand one casts a shadow… it’s surface slivering.

Meanwhile all my tests prove that I skew to the edge of the tolerance when I focus my lens. So although the tolerance is nearly 3/8 inch, my act of focusing does not place the focus in the best place. After lens focusing I should easel focus up to edge, down to edge and then settle to the center between the edges.

Regardless, that is a good practice. I was doing that for decades before I read this thread.

 

[Bill Burk]

Regardless, that is a good practice. I was doing that for decades before I read this thread.

And it’s the native way Greg focuses.

I have to make an adjustable easel. I will design it to be parallel by default but with fine adjustments for tuning, and with a release for distortion correction. No, not granite, just plain wood.

 

[Pieter12]

The left hand one casts a shadow… it’s surface slivering.

But could that be a shadow on the surface below the one that has the reticule? I don't know how close the elements are.

 

[Bill Burk]

But could that be a shadow on the surface below the one that has the reticule? I don't know how close the elements are.

Greg named it right, it’s a reflection, it will move around.

 

[DREW WILEY]

Any high-quality unit should strictly have a front surface mirror. Otherwise you get a secondary reflection. I know that replacement front-surface mirrors are still available for the top end Peak models. But in such cases, the exposed silvering is fragile, so you need to clean it very carefully. But if replacing one, even an error in adhesive thickness, if present at all, could compromise acute focus.

Bill - what is "just plain wood"? Try that expression out at your nearest lumberyard. They'll probably show you a scrap pile out back, intended for fireplaces. What I found highly useful was an early Chinese attempt at very high ply-count finish plywood. It stayed very flat due to these many well bonded thin layers, but was otherwise a marketing flop because the whole point in cabinet work for this kind of product is for sake of easily shaped exposed edges without voids, and in this case the exposed glue lines were bright red. Oops! But that oversight is no drawback in a darkroom application, especially for something stained completely black afterwards. I repurposed a scrap of that recently for yet another darkroom application. I reserve my real Euro finish birch, or maple, or mahogany for actual cabinet or furniture applications, especially now that materials are sky-high due to pandemic distribution issues.

 

[Pieter12]

Any high-quality unit should strictly have a front surface mirror. Otherwise you get a secondary reflection. I know that replacement front-surface mirrors are still available for the top end Peak models. But in such cases, the exposed silvering is fragile, so you need to clean it very carefully. But if replacing one, even an error in adhesive thickness, if present at all, could compromise acute focus.

This has gone off-track. The only reference to silver surface was about which surface of the bottom element of the focusing lens had the silver reticle (sorry, I've been misspelling it all along), never about mirrors.

 

[DREW WILEY]

Oh, thanks for the clarification.