Giles Rais

Yes, Mr Pytlak, I went over that tutorial many times, but it does not say anything about the rationale behind the way Kodak places camera stops along the Log E axis, which is exactly what I am trying to find out. According to the few characteristic curves that do come with a camera stop scale and a Log E axis, the camera stops scale for middle gray is placed along the straight line portion of the curve at seemingly random places. I know how to tell how many camera stops a given curve can give me, I just need to place them along the curve properly. As far as I am reading, the placing of middle gray ("0.0") should be where the manufacturer decides correct gamma should be, usually 0.8 for negative color (?) and that seems to be the right placement for middle gray along the scale...is this correct? Does anyvbody else have a clue? Here is my problem: for 7218, the camera stops scale shows middle gray at around 0.8 density for the red sensitive layer; for 7277 the 0.0 is placed nowhere near 0.8 density... how can one properly place the camera stop scale? Thanks again for your insights everyone!!

Dear friends: I am trying to create camera f/stop scales to characteristic curves, so that I can precisely place areas of exposure of my scene on specific sections of the curve for my stock. I know about measuring the Log E axis (in my case not only the straight-line portion of the curve, but from the beginning of the toe to the end of the shoulder, right before D-max) to obtain Log E units, and to divide those by .3 to obtain camera f/stops. The problem arises when, for instance, I have a curve that measures let's say 3 Log E units which divided by .3 gives me 10 camera f/stops. I believe that since I measured my curve from where the negative begins to react to light until it stops reacting to it, my 10 camera f/stops should be placed so that middle gray (right at the middle of my f/stop scale, marked as 0.0 by Kodak) should be right in the middle of the length of my characterisitc curve (excluding the areas of D-min and D-max). However, when I look at examples of characteristic curves that also have camera f/stops, they place middle gray in an area of the curve that is off the center of the lenght of the curve, again excluding the D-min and D-max areas (for instance, the curves for 5248 and 5246. I need to understand the rationale behind the placing of camera f/stops along the Log E axis beyond simply how to translate Log E units into f/stops. Could someone clarify this for me? I appreciate your input tremendously.