RMS Value - What Is It?

I just received the current issue of "Shutterbug" magazine and read one of the cover articles entitled "Our Top 15 Slide Films." In some of the film write-ups they mention "RMS value" and give it a number (usually 8). What does this mean?

Not something I know about, but I can Google ;)

RMS (root mean square) granularity is a widely used standard method for measuring and expressing the apparent graininess of photographic films and prints. Statistical density fluctuations in film granularity are measured, and then converted into numerical values. The lower the number, the lesser the fluctuation and the smaller the apparent grain.

Quote:

---

Originally Posted by carney2

I just received the current issue of "Shutterbug" magazine and read one of the cover articles entitled "Our Top 15 Slide Films." In some of the film write-ups they mention "RMS value" and give it a number (usually 8). What does this mean?

---

Root Mean Square is a "fancy average." For a sine wave, such as the current that comes out of an AC outlet, it is 0.707 of the peak amplitude. For film grain, its basically the same thing for "peak size of the grain." It makes sure that plus and minus values don't cancel each other out. Lower is better.

I have 2 things to say - neither of which will answer your question. :confused: But I thought I'd post them anyway.

1) It's great to see your around.......haven't seen you lately - or it's because I haven't been around as much as I used to. ;)

2) I LOVE your avatar........I've said that before. :cool:

Liz

Quote:

---

Originally Posted by carney2

I just received the current issue of "Shutterbug" magazine and read one of the cover articles entitled "Our Top 15 Slide Films." In some of the film write-ups they mention "RMS value" and give it a number (usually 8). What does this mean?

---

This certainly is a factor when scanning, but I'd still recommend trying a few out to see what works for you. Kodak always looked a lot grainier to me (E100 family) than the equivalent Fuji (Provia, Velvia but no experience with Astia) and I know the numbers are different - but there's more to it that's hard to quantify.

How bad does it say E200 is? That's the one that's got tons of grain in it - much more than Provia 400F. Curious how those numbers shake out. I wonder if bad Q.C. at labs might affect this too.

To one and all: Thanks from posting. I now have some idea of what it means. Specific responses to specific postings:

ANOTHER VIEW: The Kodak E200 got an RMS value of 12 which, as you suggest, is a little higher than other manufacturers (a lot of 8's and 9's for Fuji, for example), but is tied for the lowest number assigned to any Kodak product reviewed (tied with Kodachrome 64 which is not an E6 process).

LIZ: I have become a sporadic lurker. My contributions are way down. The only reason that I can think of is that, like photography in general, the site has a higher digital content than old time, die hard filmniks like moi are used to. People tell me that the avatar is a self portait.

MICHAEL FANELLI: Wow! You're the guy that I always wished that I'd sat next to in high school physics class.

Quote:

---

Originally Posted by carney2

MICHAEL FANELLI: Wow! You're the guy that I always wished that I'd sat next to in high school physics class.

---

LOL! Now I'm the guy teaching physics!

I also Noticed how Provia 400 was 13 when Kodachrome was only 12 (I think) Show me how far things have moved on.

Quote:

---

Originally Posted by Michael Fanelli

Root Mean Square is a "fancy average." For a sine wave, such as the current that comes out of an AC outlet, it is 0.707 of the peak amplitude. For film grain, its basically the same thing for "peak size of the grain." It makes sure that plus and minus values don't cancel each other out. Lower is better.

---

lol, that would have been my answer too :) I took electronics... not photography!

JS