BebuLamar

You're very right and thus on the other post it should be about conversion between DIN and ASA not DIN and ISO because ISO should have both values and thus need no conversion.

Picture Taker Loc: Michigan Thumb

Same numbers one "I" is international and "A" is American in the title.

Architect1776 Loc: In my mind

amfoto1 Loc: San Jose, Calif. USA

Sorry, but you remember incorrectly. ASA and ISO are identical.

There used to be ASA and DIN film speed ratings. ASA is an arithmetic progression, while DIN is logarithmic. Over the years there also were a number of less common ratings systems such as BSI (British Standard), GOST (Soviet Union), Weston, General Electric (GE) and more. ASA stands for "American Standards Association" and was mostly developed in the 1940s from two earlier film sensitivity rating systems (Weston and GE). DIN is German and stands for Deutsches Institut für Normung and it was developed in the 1930s based upon an earlier system (Scheiner). By the 1960s ASA and DIN had largely replaced all the other sensitivity rating systems (GOST was used until the 1980s).

To "simplify" things, the ISO or "International Standards Organization" film sensitivity rating system was created in 1974 and was adopted to almost entirely replace all other systems.

Initially ISO was stated combining both ASA and DIN. For example, ASA 100 is same as DIN 21 and would be stated as ISO 100/21.

Eventually this was further simplified by dropping the logarithmic DIN portion of the rating entirely. So, for example, today we just have ISO 100. And that's exactly the same as ASA 100. I forget when this happened, but know that in 1998 that ISO standard we use today became the norm for all digital cameras.

srt101fan

My feeble brain is attempting to digest all this. Nobody (with the possible exception of User ID) seems to have answered the OP's question, at least not directly.

OP: "What I would like to know is how film ASA correlates with digital ISO. I remember shooting Kodachrome 64 at much higher shutter speeds with smaller aperture’s than I am now doing with ISO’s of sometimes 200 or more."

He's asking how film speed (as expressed in ASA/ISO numbers) correlates, in practical terms with the practical application of the ISO values in a digital camera. Did he get an answer to that question? ......

boberic Loc: Quiet Corner, Connecticut. Ex long Islander

Just a difference of measuring associations nomemclature, meaning the same thing.

Sinewsworn Loc: Port Orchard, WA

Used in Europe in the 1960s and 1970s.

BebuLamar

Perhaps his memory is faulty as I shoot Kodachrome with the same settings as a digital camera at ISO 64. And yes Kodachrome. If it's Kodacolor then I would give more exposure to the film than an ISO 100 digital camera.

Badgertale Loc: Albuquerque, New Mexico, USA

ISO/ASA in digital photography is +/- gain. Not really the same thing but kind-of/sort-of.

burkphoto Loc: High Point, NC

E.L., you're old enough to remember the transition from Kodak Vericolor II to Vericolor III. That was when they switched from ASA to ISO on color negative film.

When Vericolor III came out, the box was marked ISO 160. But the 35mm and 46mm long roll films acted like Vericolor II, which was ASA 100. The 70mm long roll film with Estar base acted like it was ASA 80!

Kodak made up all kinds of excuses for what we were seeing (no shadow details and very dull highlights when the exposure was set based on a box speed of ISO 160), even stating some arcane math dealing with gamma and vagaries of slope calculations for shadow details.

Net result, as a lab, we told our customers to rate it at ISO 80 for 70mm, ISO 100 for 35 and 46mm long roll, and ISO 125 for 120/220/35 Perf. Then the 21-step gray scale Q13/Q14 chart looked as it had with Vericolor II!

Film or digital, whatever you use, MAKE TESTS to determine what works with your cameras, lenses, and processing. Results can vary a lot by serial number, make, model, and wear.

drzuvela Loc: Croatia

Also there where GOST russian nomenklature for the same purpose. About 90% of ASA value was contained in equivalent GOST value.
However, DIN norm was more in everyday use for us in Europe.

srt101fan

From Wikipedia(*) :

"Film speed is the measure of a photographic film's sensitivity to light, determined by sensitometry and measured on various numerical scales, the most recent being the ISO system. A closely related ISO system is used to describe the relationship between exposure and output image lightness in digital cameras."

"For digital photo cameras ("digital still cameras"), an exposure index (EI) rating—commonly called ISO setting—is specified by the manufacturer such that the sRGB image files produced by the camera will have a lightness similar to what would be obtained with film of the same EI rating at the same exposure."

This doesn't fully answer your correlation question except to say that, at the same film and digital ISO values, you get "similar" lightness levels in the output images.

As others have said, it's more important to get to know your camera and forget correlation.

(*) https://en.wikipedia.org/wiki/Film_speed#Digital_camera_ISO_speed_and_exposure_index

worldcycle Loc: Stateline, Nevada

Thanks everyone for your great replies, I am surprised at all the responses. I understand now that they are the "same thing" yet after watching the videos and reading the articles I am convinced that Tony Northrup is somewhat correct. Film was theoretically a constant, it was the sensor. The rating of a sensor's sensitivity by assigning an ISO number, especially considering how many technical engineering things are taking place and then expecting them all to be the same seems to be a bit ludicrous. I really find myself shooting at higher ISO's with digital than I do when I shot film (that is now using the knowledge that ISO and ASA is the same) So yes, I have already adapted to the differences, but it did raise the question and that is why I did the original post.

Picture Taker Loc: Michigan Thumb

I believe back in the early 50's in Europe my Kodak was 10ASA and Europe Film was 10 ISO. PS it vumped all the way up to 25ASA. Two and a half times as fast.

Ysarex Loc: St. Louis

In that video Tony is a clueless buffoon who gets just about everything wrong.

The ISO values on our cameras do not rate and do not apply to the sensors in our cameras. ISO establishes a standard methodology for determining the lightness of the camera output image (JPEG) that results from a measured exposure of the camera sensor. The ISO values that you can set on your __________ camera do not apply to the sensor, they apply to the camera output image. My experience is that the camera makers are reasonably consistent one to the next in their compliance with the ISO standard.