# Digital/35mm focal length question

Discussion in 'Photography' started by Gordon, Jul 3, 2007.

1. ### GordonGuest

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, Jul 3, 2007

2. ### Jürgen ExnerGuest

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

jue

Jürgen Exner, Jul 3, 2007

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-tos/convert_focal.shtml

4. ### David J. LittleboyGuest

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

David J. Littleboy

Tokyo, Japan

David J. Littleboy, Jul 4, 2007
5. ### aclGuest

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

acl, Jul 4, 2007
6. ### frederickGuest

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

frederick, Jul 4, 2007
7. ### rayGuest

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.

ray, Jul 4, 2007
8. ### Bob WilliamsGuest

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

Bob Williams, Jul 4, 2007
9. ### KoekjeGuest

David J. Littleboy enlightened us with:
It also applies to the superior APS-C cameras and the mediocre APS-C
cameras.

Koekje

Koekje, Jul 4, 2007
10. ### Tzortzakakis DimitriosGuest

And to the bottom-of-the line P&Ss<_>

Tzortzakakis Dimitrios, Jul 4, 2007
11. ### smbGuest

There are no inferior formats, there are only inferior photographers.

"Full Frame" is a misconception. The 35mm format itself is an
"inferior" format, which was originally an adaptation of movie film to
still cameras. Good photographers took hold of that format and made
it the standard it is today.

The same is true of the various APS formats. Digital is not film,
so there is no reason to think that "full-frame" digital is superior
to other formats developed for digital. There are ups and downs to
each. The only thing that matters is what you do with the format you
have.

Full-frame digital is superior for making very large prints, but it
comes with its own disadvantages. Medium format film is also
superior to 35mm film for making very large prints; but fewer
photographers use it for similar reasons to why fewer photographers
use full-frame digital.

But you know all this, David. You just like to put down anything that
is not a full-frame Canon. But sensor size is not the whole picture.
For example, the Canon 5D may have the better sensor in terms
resolution and noise reduction, but the Nikon D200 beats the 5D in
every other measurement, and it comes at a much lower price point. At
the print sizes that most of us make, the D200 can actually make more
pleasing images.

So why even fool around with an inferior full-frame system from an
office equipment company when you should be using the superior digital
medium format from *real* camera companies like Hassleblad, Pentax or
Mamiya?

Steve

smb, Jul 15, 2007
12. ### NoonsGuest

LOL!

And in 3-4 years time when most camera makers will
have ff sensor cameras out and will start dropping 1.6 and
1.5 formats, I want to see the arguments from those who
will jump in now, vociferating against you that APS-C is
not an inferior format!

Me? I'm on my second 6x7 film camera! ;-)
And the F4 and zeiss r/f continue to trod along famously.
Almost fell into a well-priced D200, but resisted
at the last moment!

Noons, Jul 15, 2007
13. ### frederickGuest

That's interesting!
Will companies like Pentax drop APS-c _and_ 35mm format digital in
favour of their 645 digital format?
Blech
6x7 film cameras suck for many things.
35mm film sucks for most.

frederick, Jul 15, 2007
14. ### smbGuest

Me, I'm still on my first 6x7 film camera. Wonderful negatives and
nice big prints can come from it. However, I rarely use it anymore
since my D200 will run circles around it in just about every shooting
situation. Point being, ultimate resolution and print size don't
mean much if you can't get the shot to begin with.

I would like to blow the dust of the 6x7 again for some nice static
landscapes and such, I'll bet those negatives scan into some nice big
digital files.

Steve

smb, Jul 15, 2007