Digital/35mm focal length question

I see conversions from digital focal length to 35mm focal length in EXIF
data on folks photo galleries, i.e. 800mm (35mm equivalent=1200mm). Is
this conversion on any kind of curve or is it a constant?

Jim

Gordon wrote:
I see conversions from digital focal length to 35mm focal length in
EXIF data on folks photo galleries, i.e. 800mm (35mm
equivalent=1200mm). Is this conversion on any kind of curve or is it
a constant?

Neither nor. It depends on the camera you are using or more precisely on the
physical size of the sensor in that camera.

jue

In article MnAii.3807$105.1146@trndny08,
"Jürgen Exner" wrote:

Gordon wrote:
I see conversions from digital focal length to 35mm focal length in
EXIF data on folks photo galleries, i.e. 800mm (35mm
equivalent=1200mm). Is this conversion on any kind of curve or is it
a constant?

Neither nor. It depends on the camera you are using or more precisely on the
physical size of the sensor in that camera.

jue

Just to followup on Jue's answer, the conversion is a constant, given a
certain-size sensor, but it differs between sensors.

E.g., APS-size sensors will have a "35mm equivalent" equal to
approximately 1.25 times the APS focal length. (A 100mm lens on an APS
sensor would give about the same results as a 125mm lens on a 35mm
sensor / film pane.) However, a small P&S sensor would have a different
conversion factor.

There are many charts available online; the conversions become important
not only with digitals but also when choosing lenses for medium- and
large-format systems.

http://www.forphotography.com/how-to...rt_focal.shtml

-Kadin.

"Gordon" wrote:
I see conversions from digital focal length to 35mm focal length in EXIF
data on folks photo galleries, i.e. 800mm (35mm equivalent=1200mm). Is
this conversion on any kind of curve or is it a constant?

It only applies to the inferior APS-C cameras, not the full-frame cameras.

David J. Littleboy

Tokyo, Japan

On Jul 4, 4:01 am, "David J. Littleboy" wrote:
"Gordon" wrote:
I see conversions from digital focal length to 35mm focal length in EXIF
data on folks photo galleries, i.e. 800mm (35mm equivalent=1200mm). Is
this conversion on any kind of curve or is it a constant?

It only applies to the inferior APS-C cameras, not the full-frame cameras.

David J. Littleboy

Tokyo, Japan

Come now, the Australian Public Service Commission has nothing to do
with this.

David J. Littleboy wrote:
"Gordon" wrote:
I see conversions from digital focal length to 35mm focal length in EXIF
data on folks photo galleries, i.e. 800mm (35mm equivalent=1200mm). Is
this conversion on any kind of curve or is it a constant?

It only applies to the inferior APS-C cameras, not the full-frame cameras.


It doesn't *only* apply to APS-c. Some large format slrs have crop
factors, unlike inferior 35mm sensor size slrs.

On Tue, 03 Jul 2007 18:26:00 -0400, Gordon wrote:

I see conversions from digital focal length to 35mm focal length in EXIF
data on folks photo galleries, i.e. 800mm (35mm equivalent=1200mm). Is
this conversion on any kind of curve or is it a constant?

Jim

That is a constant factor which can be different for different cameras. It
depends on the size of the sensor in the camera, and there are quite a few
different sensor sizes.

Gordon wrote:
I see conversions from digital focal length to 35mm focal length in EXIF
data on folks photo galleries, i.e. 800mm (35mm equivalent=1200mm). Is
this conversion on any kind of curve or is it a constant?

Jim

The conversion factor is equal to the ratio of the diagonal of 35 mm
film (43.3mm) to the diagonal of the sensor in the camera of interest(x
mm). Factor = 43.3 / x.
Bob Williams

["Followup-To:" header set to alt.photography.]
David J. Littleboy enlightened us with:
It only applies to the inferior APS-C cameras

It also applies to the superior APS-C cameras and the mediocre APS-C
cameras.

Koekje

Ï "David J. Littleboy" Ýãñáøå óôï ìÞíõìá
...

"Gordon" wrote:
I see conversions from digital focal length to 35mm focal length in EXIF
data on folks photo galleries, i.e. 800mm (35mm equivalent=1200mm). Is
this conversion on any kind of curve or is it a constant?

It only applies to the inferior APS-C cameras, not the full-frame cameras.

And to the bottom-of-the line P&Ss_



--
Tzortzakakis Dimitrios
major in electrical engineering
mechanized infantry reservist
dimtzort AT otenet DOT gr