ISO Speed XP2

[nickc1]

<p>Sitting here over the holiday, and waiting until Monday to get a couple of rolls of Ilford XP2 processed I was wondering what peoples opinions of the 'true' speed of XP2 might be. I usually shoot at an EI of 250, and the box says 400, but as a C41 film it will cope well with over exposure, so the actual ISO speed would be 100? 200? or what.<br>

I have no real need for an answer, but I am intrigued to read anyones suggestion, and their logic behind it, purely to help me in my own musings.<br>

Happy Christmas/Chanukah/New Year to you all - Nick</p>

[craig_shearman1]

<p>The "actual" ISO is what the manufacturer says it is -- 400. Being able to tolerate a couple of stops over or underexposure doesn't change the ISO. An ISO rating is developed under specific scientific objective standards that result in a given density for a given amount of development and a given exposure. If you want to use a different number that works for you because of differences in the way you meter, expose, develop, etc., that's fine but it's called an "exposure index" not an ISO. But the ISO remains the same.</p>

[nickc1]

<p>Sorry, but I must beg to differ - hence my inquiry. Agreed that the ISO speed is how a film responds to a standard test, it is very definitely not what a manufacturer says it should be, but the reason behind my question was that as c41 films are all developed in a standard way, development cannot be a factor. Also as c41 films are usually good for -1stop to +5stops and they usually do not respond well to under exposure, I am guessing that the 'natural' speed of XP2 is lower than the ISO result suggests if it can be exposed at an EI of between 100 - 800 (-2 stops to +1 stop) according to the manufacturer - I was just seeing if anyone else had any suggestions to reinforce this guess.</p>

[ronald_moravec1]

<p>Craig gave you the correct answer - 400. 100 will be a very heavy negative reguiring long printing times. 800 will start to drop out shadows.</p>

<p> </p>

[nickc1]

<p>Sorry guys - Thanks for the answers and help, but I think I need to rephrase my question to get suggestions to answer the (theoretical) concept I was musing over.<br>

In practical terms I am happy with my negs at ISO 250.<br>

If I can put my uncertainty into a clearer form I'll try again - Thanks for you help and take care.</p>

[gary_watson]

<p>The received wisdom about XP2 was that over-exposure reduced grain and widened tonal range, so XP2 "rated" at 100-250 gave more than acceptable results. I rate 120 chromogenics(Kodak and Ilford)at 100 under studio lighting and get no complaints about "heavy" negatives from my lab. Box rating(i.e., 400) results in near under-exposure and somewhat murky prints.</p>

[r.t. dowling]

<p>I was never a big fan of XP2, but when I shot it, I got the best results at 250. When I shot it at 400, it looked significantly grainier than Kodak BW400CN shot at 400. Which is why I preferred the Kodak when I had a choice between the two.</p>

[matthew_newton]

<p><a href="http://www.ilfordphoto.com/Webfiles/20061301945161573.pdf">http://www.ilfordphoto.com/Webfiles/20061301945161573.pdf</a><br />Read there. According to Ilford you can expose it at anywhere from ISO100 for super fine grain to ISO800 for a grainier picture. I've done everything from ISO100 to ISO1250 with it with good results (I generally rate it at ISO400, but I'll go lower for portraits, etc sometimes and higher if I need the light or want to go grainy on a shot). Here are a couple examples.</p><div></div>

[matthew_newton]

<p>Another example</p>

[matthew_newton]

<p>As you can see at ISO200 it is pretty grain free even in the shadows and the highlights aren't really blown, even on the white sweeter (its easier to see this on the actual print/negative, I scanned the 4x6 using a crappy flat bed). In the ISO1250 picture the highlights are okay, but the shadows are pretty darned grainy, but in my opinion not terribly objectionable (they are grainy).</p><div></div>

[glen_ford]

<p>i shoot this film for professional applications and tend to stick around iso 200, although i will use anywhere between 100 and 800 according to the situation. The fact that you can shoot different frames at different iso ratings and just get the film developed normally is great.</p>

[frank.schifano]

<p>Look, what Craig wrote is absolutely true. The ISO rating is the ISO rating. It translates to a specific density under controlled exposure and development conditions. I do not know what the precise numbers are, nor will I even begin to speculate about the subject. The speed at which you decide to rate the film does not change the ISO rating. The speed at which you rate the film, for better or worse, is the exposure index, not the ISO rating. ISO is an acronym for International Organization for Standardization. You think there might be a clue in that name somewhere?</p>