high silver film, truer to rating?

[e_joyner]

Anybody have thoughts to whether higher silver content films are truer to their ISO rating? I love APX, but ran into problems when they changed emulsions. Too much contrast! I altered agitation, but it was still too contrasty.

I've been trying to hone my developing skills, then I stumbled onto Barry Thornton's website. I did my first ISO/developing test on Delta 100 120 film. I'm not done yet, but the experiment is very interesting. I haven't had time to start testing on APX (35mm) yet. I did take a wild guess and developed my last roll for 20% less time-(from Digitaltruth the time for D-76 1:1 is 13.5 min)-so I developed for 11 min. I am much happier with the results. I've been pouring over their data sheets, and they say their film is accurate to +/-1/6 stop(I think that's right). When you read the developing recommendations, it shows a slightly higher effective ISO rating using the time/soup guide.

I *do* plan on doing testing following Barry's outline, but was wondering if any of you have tested APX and what were your observations. I know it's 'subjective', I'm just curious.

Sorry about the seemingly endless questions in this post.

edye

 

[gma]

I am curious to read about what others have observed, but I think some manufacturers' speed ratings are exagerated strictly for marketing purposes. I always expose at lower EI's than published.

 

[rjr]

I am curious to read about what others have observed, but I think some manufacturers' speed ratings are exagerated strictly for marketing purposes. I always expose at lower EI's than published.

IMHO that´s true, with two exemptions.

- 100ASA color negative films of all brands usually have an actual rating of around 160ASA

and

- the Adox/Efke type emulsions are faster than the package print and don´t like being overexposed.

With bw it heavily depends on what developer you choose to use. APX100 (in Rodinal) and Scala (in Scala reversal process) pretty much fulfill their promises.

 

[chrisg]

With normal (seven stop) scenes I've found HP5 is fine at 400 when developed in D76. I rate it at 200 or 250 for reduced development time with nine stop scenes. I get an extra stop out of it when I develop with DDX.

I rate FP4 at 100 with D76. DDX seems to give it an extra stop as well.

As indicated in the previous, the developer can make big difference.