Equivalent focal lengths

Michelle Steiner wrote:
I currently have a Nikon 35mm SLR, so when I get a digital SLR, it will
also be a Nikon so I can interchange the lenses between the cameras.
I'm pretty much settled on the D70.
My question is, if I put my current 50mm on a D7, what would its
equivalent focal length to a 35mm camera be?

75 mm (roughly, as the multiplier is not exactly
but very close to 1.5 x)


Juergen

Michelle Steiner wrote:

I currently have a Nikon 35mm SLR, so when I get a digital SLR, it will
also be a Nikon so I can interchange the lenses between the cameras.
I'm pretty much settled on the D70.

My question is, if I put my current 50mm on a D7, what would its
equivalent focal length to a 35mm camera be?

It'd be equal to a 75mm lens.

--
John McWilliams

Michelle Steiner wrote:
John McWilliams wrote:
My question is, if I put my current 50mm on a D7, what would its
equivalent focal length to a 35mm camera be?
It'd be equal to a 75mm lens.
Thanks.
Does that 1.5 : 1 ratio hold true for all focal lengths? Would my 85 mm
lens be equivalent to a 127.5 mm lens?

Yes.


Juergen

Michelle Steiner wrote:

I currently have a Nikon 35mm SLR, so when I get a digital SLR, it will
also be a Nikon so I can interchange the lenses between the cameras.
I'm pretty much settled on the D70.

My question is, if I put my current 50mm on a D7, what would its
equivalent focal length to a 35mm camera be?

For the D70:

In x the multiplier would be 36mm /23.7mm, or about 1.52.
In y the multiplier would be 24mm /15.5mm, or about 1.55.

Split that and you get 1.53.

Just multiply the FL of the lens by that number to get the 'equivalent'.

50 x 1.53 = 76.5mm
100 x 1.53 = 153mm

and so on.

Cheers,
Alan

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My question is, if I put my current 50mm on a D7, what would its
equivalent focal length to a 35mm camera be?

It'd be equal to a 75mm lens.

Thanks.

Does that 1.5 : 1 ratio hold true for all focal lengths? Would my 85 mm
lens be equivalent to a 127.5 mm lens?

Yes, it's always x1.5, but you should also know that a 50mm lens on
your digital Nikon will not behave exactly the same way a 75mm does on
a film camera. The way to think of it is this: you're still shooting
with a 50mm lens, but you're always cropping to end up just using the
middle part of the picture.

-Joel

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Michelle Steiner wrote:
In article ,
(Dr. Joel M. Hoffman) wrote:

Yes, it's always x1.5, but you should also know that a 50mm lens on
your digital Nikon will not behave exactly the same way a 75mm does
on a film camera. The way to think of it is this: you're still
shooting with a 50mm lens, but you're always cropping to end up just
using the middle part of the picture.

But the cropping is optical, before the image is captured; that's not
the same as cropping with an enlarger (film) or with software
(digital).

Why not?

Michelle Steiner wrote:
In article ,
"David J Taylor" wrote:

But the cropping is optical, before the image is captured; that's
not the same as cropping with an enlarger (film) or with software
(digital).

Why not?

Because when you crop the captured image, you're increasing the pixel
size, thus reducing the sharpness.

If a CCD sensor is smaller than a full 35mm frome (36 x 24mm), then the
area which the sensor sees is just the same as cropping the 35mm negative
in an enlarger, or cropping a full-frame CCD sensor image in software.

David

Michelle Steiner writes:

In article ,
"David J Taylor" wrote:

But the cropping is optical, before the image is captured; that's
not the same as cropping with an enlarger (film) or with software
(digital).

Why not?

Because when you crop the captured image, you're increasing the pixel
size, thus reducing the sharpness.

"increasing pixel size" ? Not unless you decide to, post-crop, change
the output area over which those pixels are projected.

If you take a CCD which is less than a 35mm frame and print it out at,
say 12"x8", the output projections of those pixels are going to be
larger than if you had the same sized sensor elements spread over a
whole 35mm frame (and thus if you had more of them).

So, in effect, the digital case is identical.

I suggest you try being a little clearer about precisely what you mean
by 'pixel size' because it appears than you're confusing yourself.

B

Bruce Murphy wrote:
Michelle Steiner writes:


In article ,
"David J Taylor" wrote:


But the cropping is optical, before the image is captured; that's
not the same as cropping with an enlarger (film) or with software
(digital).

Why not?

Because when you crop the captured image, you're increasing the pixel
size, thus reducing the sharpness.


"increasing pixel size" ? Not unless you decide to, post-crop, change
the output area over which those pixels are projected.

If you take a CCD which is less than a 35mm frame and print it out at,
say 12"x8", the output projections of those pixels are going to be
larger than if you had the same sized sensor elements spread over a
whole 35mm frame (and thus if you had more of them).

So, in effect, the digital case is identical.

I suggest you try being a little clearer about precisely what you mean
by 'pixel size' because it appears than you're confusing yourself.


Relax, Bruce. The OP's original point, lost recently, was that there's a
difference between the cropping that can occur in the *viewfinder* vs.
post production, if you will, cropping. That's true of both pixels and
grains.

--
John McWilliams

Michelle Steiner wrote:

I'm not comparing the same focal length on different sensor or film
sizes; I'm comparing different focal lengths on the same film or sensor
size.

This sub thread is in a semantic tangle over the word "crop". Don't worry about it.

For the D70 the effective multiplier is approx. 1.53 for every lens FL.

Thus 50mm - 76.5mm effective. (1.5 is close enough as few lenses stated to be
a specific FL are actually that specific FL ... a couple mm either way is common).

Cheers,
Alan.

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-- [SI] gallery & rulz: http://www.pbase.com/shootin
-- e-meil: there's no such thing as a FreeLunch.