Investigating ISO 100 (E-M5)

Started 9 months ago | Discussions thread
ForumParentFirstPreviousNextNext unread
Flat view
Thomas Niemann
Veteran MemberPosts: 4,097
Like?
Investigating ISO 100 (E-M5)
9 months ago

I had two questions concerning the ISO 100 feature implemented in firmware 2.0 for the E-M5.

How does highlight recovery differ when shooting ISO 100 and 200 for Raw files?
How does highlight recovery differ when shooting ISO 100 and 200 for JPEG files?

I photographed the following image under a full-spectrum light varying exposure in one-third stop increments.

Of interest are the design elements above the pureJill logo. Increasing exposure until I could no longer distinguish any elements would be the cutoff. Later, when processing the images in Photoshop CC ACR I decreased Highlights and Whites to -100 in an attempt to retrieve blown highlights. This same correction was applied to both JPEG and Raw files. I didn't adjust the Exposure slider since I was trying to retrieve highlights without modifying midtones.

For ISO 100 base exposure was twice as long as the exposure for ISO 200. The following 3 images illustrate, for ISO 200 Raw files, three exposures. The left image is 8 one-third stops above base exposure, center image is 9 one-third stops, and the right image is 10 one-third stops above base exposure. While the center image was close, all detail didn't blow out until the image on the right.

Under these circumstances the following chart indicates the number of one-third stop increments, above base exposure, that were required to blow-out design details. For example, at ISO 100 the Raw exposure was 7 one-third stops higher than base exposure. That is, 7 x 1/3 = 2 1/3 stops higher.

From this we can deduce the following:

For Raw files, at ISO 100 we can retrieve one stop more detail than JPEGs. (7 - 4)/3
For Raw files, at ISO 200 we can retrieve one stop more detail than JPEGs. (10 - 7)/3
For Raw files, at ISO 200, we can retrieve one stop more detail than at ISO 100. (10 - 7)/3
For JPEG files, at ISO 200, we can retrieve one stop more detail than at ISO 100. (7 - 4)/3

ForumParentFirstPreviousNextNext unread
Flat view
Post (hide subjects)Posted by
ForumParentFirstPreviousNextNext unread
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark post MMy threads
Color scheme? Blue / Yellow