Ok, so confession time...my acutance issues may be due to an oversight on my part due to my much (un)loved Omega C760's negative stage and my ageing eyes.
When all fails, check everything....and maybe some other stuff too...
My C760 is bolted to the wall using a wall support base on the bottom of the column and top mount for the column head which together rigidly attaches the column to the wall.
However, that wall is subject to load from above and unfortunately part of that load is a torture test: our washer and dryer are on the floor above the basement darkroom and that wall is hung from the joists of the floor above.
So, the wall is subject to periodic vibration which shouldn't be a problem as long as I'm not printing while laundry is in-process, but it seems that the highly "adjustable" negative stage in the C760 shifts it's negative stage alignment as the result of it's less than optimal engineering.
Specifically, the negative stage is designed with a sprung base under the negative carrier and relies upon the lamphouse positioning to hold the negative holder in alignment using 4 adjustment screws at the back of the lamphouse. These screws are quite difficult to use to align the lamphouse and negative carrier (even with a laser alignment tool) and quite apparently, and I've now determined will shifting due to vibration.
After checking and re-aligning the enlarger last night and reprinting a 120 TMX neg developed in Perceptol 1:3, the 16x20 test size enlargement is crisp, sharp, smooth and detailed everywhere, especially in off-centre parts of the image that are best to evaluate acutance.
Lesson learned - I'll confirm alignment before any meaningful printing session.
When all fails, check everything....and maybe some other stuff too...
My C760 is bolted to the wall using a wall support base on the bottom of the column and top mount for the column head which together rigidly attaches the column to the wall.
However, that wall is subject to load from above and unfortunately part of that load is a torture test: our washer and dryer are on the floor above the basement darkroom and that wall is hung from the joists of the floor above.
So, the wall is subject to periodic vibration which shouldn't be a problem as long as I'm not printing while laundry is in-process, but it seems that the highly "adjustable" negative stage in the C760 shifts it's negative stage alignment as the result of it's less than optimal engineering.
Specifically, the negative stage is designed with a sprung base under the negative carrier and relies upon the lamphouse positioning to hold the negative holder in alignment using 4 adjustment screws at the back of the lamphouse. These screws are quite difficult to use to align the lamphouse and negative carrier (even with a laser alignment tool) and quite apparently, and I've now determined will shifting due to vibration.
After checking and re-aligning the enlarger last night and reprinting a 120 TMX neg developed in Perceptol 1:3, the 16x20 test size enlargement is crisp, sharp, smooth and detailed everywhere, especially in off-centre parts of the image that are best to evaluate acutance.
Lesson learned - I'll confirm alignment before any meaningful printing session.