Digital 17mm Is Not Equivelent 27mm on 35mm Film
 

Just realised that even though manufactures give 35mm equivalents, it is not
really true.

If you shoot tall buildings at 17mm on digital (with 1.6 crop factor), you
still get distorted pics just like 17mm lenses on 35mm film cameras.

"A" wrote in message
...
Just realised that even though manufactures give 35mm equivalents, it is
not
really true.

If you shoot tall buildings at 17mm on digital (with 1.6 crop factor), you
still get distorted pics just like 17mm lenses on 35mm film cameras.

The "equivalents" really only apply to *field of view,* since you're really
just cropping out the middle portion of the normal 35mm film camera's image.

"A" wrote in message
...
Just realised that even though manufactures give 35mm equivalents, it is
not
really true.

If you shoot tall buildings at 17mm on digital (with 1.6 crop factor), you
still get distorted pics just like 17mm lenses on 35mm film cameras.

The "equivalents" really only apply to *field of view,* since you're really
just cropping out the middle portion of the normal 35mm film camera's image.

"Mark²" mjmorgan(lowest even number wrote in message
news:FL3xd.59115$ka2.18959@fed1read04...

"A" wrote in message
...
Just realised that even though manufactures give 35mm equivalents, it is
not
really true.

If you shoot tall buildings at 17mm on digital (with 1.6 crop factor),
you
still get distorted pics just like 17mm lenses on 35mm film cameras.

The "equivalents" really only apply to *field of view,* since you're
really
just cropping out the middle portion of the normal 35mm film camera's
image.

I assume most of you know this, but I didn't until I read it in a book. If
you tilt the camera up when taking a tall building, the resulting 'falling
back effect" can be corrected using the deform tool in a photo editor, with
some reduction of picture content. Sort of like having an old swing and tilt
plate camera (which I bet would do a better job).
Dave Cohen

"A" wrote in message
...
Just realised that even though manufactures give 35mm equivalents, it is
not
really true.

If you shoot tall buildings at 17mm on digital (with 1.6 crop factor), you
still get distorted pics just like 17mm lenses on 35mm film cameras.


It's the biggest misconception in digital photography. People think a
smaller sensor somehow changes the optics of the lens. Film or digital --
it's the same light projected through the same lens, you just use a smaller
piece of it with the digital.

You used the term "crop factor." That's what it's all about.

Good shooting,
Bob Scott

"A" wrote in message
...
Just realised that even though manufactures give 35mm equivalents, it is
not
really true.

If you shoot tall buildings at 17mm on digital (with 1.6 crop factor), you
still get distorted pics just like 17mm lenses on 35mm film cameras.


It's the biggest misconception in digital photography. People think a
smaller sensor somehow changes the optics of the lens. Film or digital --
it's the same light projected through the same lens, you just use a smaller
piece of it with the digital.

You used the term "crop factor." That's what it's all about.

Good shooting,
Bob Scott

"Dave Cohen" wrote in
news:1103417385.c5fa8a62fb815db7e0b4afea6ffddb7d@t eranews:

Sort of like having an old swing and tilt
plate camera (which I bet would do a better job).


Yeah. Somehow using a view camera with it's movements produces a different
picture than taking a digital photo and manipulating it. My wild guess is
it might have something to do with lens distortion.

I have noticed, at least with some images, if you do a simple perspecive
change in software, some of the lines that should be parallel with others
end up pointing in different directions.

Bob

--
Delete the inverse SPAM to reply

"Dave Cohen" wrote in
news:1103417385.c5fa8a62fb815db7e0b4afea6ffddb7d@t eranews:

Sort of like having an old swing and tilt
plate camera (which I bet would do a better job).


Yeah. Somehow using a view camera with it's movements produces a different
picture than taking a digital photo and manipulating it. My wild guess is
it might have something to do with lens distortion.

I have noticed, at least with some images, if you do a simple perspecive
change in software, some of the lines that should be parallel with others
end up pointing in different directions.

Bob

--
Delete the inverse SPAM to reply

Dave Cohen wrote:

I assume most of you know this, but I didn't until I read it in a book. If
you tilt the camera up when taking a tall building, the resulting 'falling
back effect" can be corrected using the deform tool in a photo editor, with
some reduction of picture content. Sort of like having an old swing and tilt
plate camera (which I bet would do a better job).
Dave Cohen

Not many people know that movements on a LF camera (swing and tilt) introduces
distortion into the image, by altering the aspect ratio of the subject. The
converging - sometimes diverging - lines can be corrected with movements, but at
the expense of the building or whatever being rendered taller, and the
foreground over large.

Perspective correction can be done in Photoshop with Transform tools, and the
image aspect ratio can be corrected as well with Image Size by un-ticking
Constrain Proportions, and adjusting either height or width as appropriate.
It's up to the operator how he decides when it is correct, but it can be done.

Colin

It's the biggest misconception in digital photography. People think a
smaller sensor somehow changes the optics of the lens. Film or digital --
it's the same light projected through the same lens, you just use a smaller
piece of it with the digital.

Bob-

Funny you should mention that. Another related misconception is that sensor
size is not as important as the number of megapixels. In other words, it is OK
to have a small sensor if you have enough megapixels.

Thirty years ago lenses were rated in "lines per millimeter". I don't fully
understand the more modern modulation transfer ratio (MTR), but I can relate
lines to pixels. So, above a certain number, no matter how many pixels you
have, the image resolution is limited by the lens resolving power. Fewer
sensor millimeters means fewer "lines" in the resulting image. This is another
flaw in the claim of 35 mm equivalency since you would divide lines per
millimeter by the cropping factor.

Perhaps it wasn't a significant factor when sensors were no more than one
megapixel, but is certainly is in today's eight to ten megapixel world.

Fred