kobra Posted January 22 Share #1 Posted January 22 (edited) Advertisement (gone after registration) Hi all, Rather than taking away from "Robbs Leica Adventures" thread, I've started a new one here. In the thread by @robb, @hansvons posted some very detailed comments on ISO and I would like to know more. I hope it's ok that I quoted this part of the post here: "(The SL2-S sensor is invariant from EI 100-3200. Only after that signal amplifying kicks in. In that bracket, one only moves the middle grey up and down, or to say it in analogue film terms, the sensor's ISO is fixed, and you over or underexpose the film all else equal as you would with exposure compensation or a different EI rating compared to the box speed. ISO 50, on the other hand, is out of that bracket and inevitably leads to overexposure and thus needs exposure compensation of -1 stop to bring it back. In other words, with ISO 50, one is sacrificing one stop of DR on the highlights end for nought, as ISO 50 offers no advantage over ISO 100 in terms of noise. But even with ISO 100, one has no leeway on the highlights end, and accidental overexposure will inevitably lead to lost information in the highlights. That's why I find using the base ISO (here ISO 100) as a safe haven problematic, as the term "base" is misleading. I prefer ISO 800 for the most motives because I like the texture I get without losing the SL2-S' rich colour in the shadows. If lustre and cleanliness to the max are the goals, ISO 200 fits. Otherwise, ISO 400 gives you a balanced, full DR from the shadows to the highlights with the best signal-to-noise ratio in high-contrast environments such as a city park on a sunny day. The question remains: what is the SL2-S "box speed"? From my experience, that's somewhere between ISO 400 and ISO 800. From there, an informed decision can be made about which EI suits the targeted result best.)" BTW, wonderful and detailed explanation @hansvons! Here are some followup questions (I admit to not fully understanding ISO invariance): -I've always thought that "base ISO" (ie 100) gives the widest DR, but it seems ISO 200 or 400 may be better? -how does ISO 200 give more lustre and cleanliness than ISO 100? Is it because it may be easier to preserve the highlights? -what is "box speed"? -what differences might there be between the ISO performance of the SL2 vs the SL2-S? (in the context of the above "lower ISO" ranges; I know high ISO favors the SL2-S) My apologies if this is covered in another thread, but I've not found the above gems when I searched. Thanks in advance for helping me understand this better! Brad Edited January 22 by kobra robb and LEGEND 2 Quote Link to post Share on other sites More sharing options...
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.