steel developing tanks: none with possibility for central rod?

The agitation of developer is certainly a hot topic, understandably. So many different variations, so little time. I too, struggle with this topic. I’ve been using 510 Pyro with some success, evenness being the devil as I tend to like a big sky in my work.

I really don't understand why anyone should struggle with such a simple concept as mixing fresh(er) developer with the used stuff that clings to the surface of the film. True, there are a variety of ways of achieving this, some more efficient than others, but basically all you're attempting to do is mix fresh developer with stale. And in a tank that allows inversion agitation, that's a very simple thing to do.

1) Do not overfill the tank. Leave about 10% of the volume as air-space. Following the maker's recommended volume of solution does this.

2) Use the number of reels the tank is designed to take - even if some of them are empty. A few millimetres of 'slack' between reel and tank lid don't matter, but you obviously don't want a single reel slopping from bottom to top of a 4 reel tank when you invert it.

3) Invert the tank smartly. No silly wrist gyrations or slow motion actions are needed, nor in any way useful.

4) Hold the tank upside down long enough for the airspace and liquid to exchange places. A slow count of two is usually enough time.

5) Right the tank just as quickly as you inverted it.

6) Give the tank a quick knock on its base to dislodge any air 'bells' that may have stuck to the film.

7) Repeat steps 3 to 6 as many times per minute as you think suitable or advisable.

Personally I use 2 inversion cycles per minute. Some people only agitate once per minute, others prefer more. As long as you're consistent I don't think it matters too much. And it depends on the developer and film used - For example, a 20 minute development time needs less inversions per minute than a 4 minute total time.

Just use some common sense! Something that seems to go right out of the window when film development gets discussed.

WRT evenness of skies: It's easy to confuse natural sky tone variation or lens vignetting with development unevenness. Remember, there are very few lenses that don't show some vignetting unless stopped down to a tiny aperture... and even then....