Up until recently, I had been using a CombiPlan plastic film holder for 6 4x5" films and developing using a multi-tank array. I agitated by raising and lowering the film holder in the developer 3 times every 30 seconds. I had tested my film development more or less according to BTZS using a Stouffer step wedge and measuring the gradient at different developing times. Even though the Stouffer wedge has two fields with identical density, the results on my test negatives were always somewhat off (0.02 to 0.04 as measured on my Heiland densitometer). My curves were also somewhat uneven. I attributed this to measurement error, although I checked the densities on the Stouffer wedge several times and always got identical results. I got tired of developing in the dark and wanted to try the JOBO rotation system, which of course also uses less chemicals (my tank array required 1200ml to cover the film holder fully). So I splurged and bought a brand new JOBO CPP-2 with lift and a JOBO 3010 Expert Drum. I did a test run this weekend to check development times with the #4 speed rotation as recommended by JOBO for this drum. To my surprise, I got very smooth curves (see attachment) and the results for the duplicate density field were identical on all my test negatives. Looking back at some of the images I developed over the last few months, I realize that I often have visible effects which I attributed to uneven lighting due to clouds that I had not noticed when taking the picture. So now I realize that these effects and the uneven density results were due to uneven development using the CombiPlan holders. I am happy to have found that I can improve the quality of my negatives with the new system, but am also very unhappy knowing that there was uneven development with the nearly 400 4x5 sheets I have developed since I got the CombiPlan system (I used to use tray development). Now I need to set my new standard developer for the JOBO developing system for my normal film (FP4+). XTOL 1:1 gave me too short times with FP4+ using rotation. I aim for a gamma of 0.57 for normal development and like to have room for at least N+2 and N-1, but I am at nearly normal development with only 5 minutes. So I will either try more dilute XTOL (1:3) or another developer. I have read that at least 25ml of XTOL stock should be used per 4x5 film, so with 10 films I would need 250ml + 750ml water which is the maximum volume rated for the 3010 drum (minimum only 210ml). Or maybe I will try another developer, anyone have suggestions for rotation processing FP4? I like to have developing times of around 10-12 minutes for normal contrast so I have plenty of room on both sides. So for anyone else considering the CombiPlan system - I would recommend don't!