Velocity Reviews (http://www.velocityreviews.com/forums/index.php)
-   Digital Photography (http://www.velocityreviews.com/forums/f37-digital-photography.html)
-   -   Should 4/3 lenses be half the size of full frame lenses? (http://www.velocityreviews.com/forums/t749879-should-4-3-lenses-be-half-the-size-of-full-frame-lenses.html)

 bob 06-13-2011 03:48 PM

Should 4/3 lenses be half the size of full frame lenses?

4/3 camera has a sensor that is about half the length and height of a full
frame sensor (1/4 the area).

Does that mean a 4/3 camera lense would be half the diameter of an
equivalent full frame lense?

 David J Taylor 06-13-2011 04:14 PM

Re: Should 4/3 lenses be half the size of full frame lenses?

"bob" <nospam@hotmail.com> wrote in message
news:it5bhf\$djb\$1@speranza.aioe.org...
> 4/3 camera has a sensor that is about half the length and height of a
> full frame sensor (1/4 the area).
>
> Does that mean a 4/3 camera lense would be half the diameter of an
> equivalent full frame lense?

... and half the length, and one eighth of the weight! Doesn't seem to be
so in practice, though. You also use the word "equivalent". To be
equivalent in light gathering power an f/2.8 full-frame lens would need to
be replaced by an f/1.4 half-frame lens. Somewhat more costly to make, if
possible at all.

Cheers,
David

 David J Taylor 06-13-2011 06:31 PM

Re: Should 4/3 lenses be half the size of full frame lenses?

"David Dyer-Bennet" <illegalname@gmail.com> wrote in message
[]
> We've been around on this before, haven't we? It sounds familiar.

Yes, perhaps the OP might like to consult the archives.

> Because it's scaled by the focal length, the f number means the
> same thing for any format, *In terms of exposure*. A micro 4/3
> f/2.8 lens is exactly equivalent to a full-frame f/2.8 lens *in that
> regard*.
> When I mount my Nikon 50/1.8 (via an adapter) to my
> Micro 4/3 camera, the marked f numbers on the lens aperture
> ring remain correct.
>
> So I'm not sure what you mean by "light gathering power".
>
> That's the equivalence most people care about when discussing
> this issue, but of course it's not the only one. I vaguely remember
> that you insist on f/1.4 to be able to get equally shallow
> depth of field, or something? (Unless I'm confusing you with
> somebody else, in which case my apologies to both you and
> the unknown other person.) I haven't chased through the details
> myself, but I have no reason to doubt you.
>
> Still, flatly telling people that f/1.4 on a micro 4/3rds lens is
> equivalent to f/2.8 on a full-frame lens is just plain wrong.

Which is why I asked the OP to clarify what they meant by "equivalent".
For the same number of photons on the sensor, what I say is correct.

I haven't done the depth of field sums - that was likely Roger Clarkson.

Cheers,
David

 David J Taylor 06-13-2011 06:40 PM

Re: Should 4/3 lenses be half the size of full frame lenses?

"Bruce" <docnews2011@gmail.com> wrote in message
news:flicv6papmkkhklulgurdh8gb36c8qoju7@4ax.com...
[]
> You're showing your (profound) ignorance again, David.
>
> The light gathering power of an f/2.8 Four Thirds lens is identical to
> an f/2.8 APS-C lens, an f/2.8 full frame lens and an f/2.8 medium
> format lens, regardless of focal length.
>
> The clue is in the term "f/".
>
> Perhaps you should stick to enjoying your consumer grade DSLR and your
> consumer grade lenses, and stop dispensing consumer grade "advice".

Lenses with the same f/number (more strictly, T/number) will deliver the
same number of photons per unit area, but as the full-frame sensor has
four times the sensitive area of the half-frame sensor, it gathers four
times as much light - four times as many photons. To get the same number
of photons, you need a lens with twice the physical opening, four times
the aperture area, and one half the numeric f/number.

It's why small sensor cameras need a higher light level to get the same
signal-to-noise ratio or, put another way, why they are noisier at higher
ISOs. Their smaller sensor captures fewer photons for a given f/number
and light level.

 David Dyer-Bennet 06-13-2011 09:20 PM

Re: Should 4/3 lenses be half the size of full frame lenses?

On Jun 13, 1:40*pm, "David J Taylor" <david-
tay...@blueyonder.co.uk.invalid> wrote:
> "Bruce" <docnews2...@gmail.com> wrote in message
>
> news:flicv6papmkkhklulgurdh8gb36c8qoju7@4ax.com...
> []
>
> > You're showing your (profound) ignorance again, David.

>
> > The light gathering power of an f/2.8 Four Thirds lens is identical to
> > an f/2.8 APS-C lens, an f/2.8 full frame lens and an f/2.8 medium
> > format lens, regardless of focal length.

>
> > The clue is in the term "f/".

>
> > Perhaps you should stick to enjoying your consumer grade DSLR and your
> > consumer grade lenses, and stop dispensing consumer grade "advice".

>
> Lenses with the same f/number (more strictly, T/number) will deliver the
> same number of photons per unit area, but as the full-frame sensor has
> four times the sensitive area of the half-frame sensor, it gathers four
> times as much light - four times as many photons. *To get the same number
> of photons, you need a lens with twice the physical opening, four times
> the aperture area, and one half the numeric f/number.

You're assuming the same pixel count, which is regrettably frequently
true, but is not an inherent aspect of sensor size. I think a lot of
the
confusion arises from your relating the issue to sensor size
rather than pixel size (okay, sensel size).

Same number of photos per unit area is what matters for exposure.
"Everybody knows" this and it's true, as true as anything is anyway.
Your statements always start out looking like they're trying to
deny this, which gets everybody up in arms, because this really
*is* true.

> It's why small sensor cameras need a higher light level to get the same
> signal-to-noise ratio or, put another way, why they are noisier at higher
> ISOs. *Their smaller sensor captures fewer photons for a given f/number
> and light level.

Hmmm; this feels like a back-door way of coming at the problem, and
also
doesn't give me any help in minimzing noise -- both my cameras have
a base ISO of 200, so I can't turn down the ISO in either case.

But one of them is a Nikon D700, and one is an Olympus E-PL2. I know
which one is noisier at high ISO! It's the one with the smaller
pixels,
which in this case is the one with the smaller sensor. (They're also
the
same number of pixels, so that makes all sorts of comparisons easy.)

Signal-to-noise ratio isn't a stated spec or anything we have a
standard
for measuring in cameras (that's widely used and understood, anyway).

It's generally true that, for any given technology, smaller pixels
will be
noisier at ANY ISO (than larger pixels at that same ISO). Won't
argue
against that for a moment.

But despite having been around this course before, I still wasn't
able to read that out of your initial statements. It'd maybe be good
to work on how you present this issue, to avoid the initial confusion
and opposition.

 David J Taylor 06-14-2011 05:58 AM

Re: Should 4/3 lenses be half the size of full frame lenses?

"David Dyer-Bennet" <illegalname@gmail.com> wrote in message
[]
> You're assuming the same pixel count, which is regrettably frequently
> true, but is not an inherent aspect of sensor size. I think a lot of
> the
> confusion arises from your relating the issue to sensor size
> rather than pixel size (okay, sensel size).

Pixel count actually has nothing to do with it. It's the sensor area
which matters. Pixel count sets how you trade-off spatial resolution for
signal-to-noise ratio at the pixel level.

> Same number of photos per unit area is what matters for exposure.
> "Everybody knows" this and it's true, as true as anything is anyway.
> Your statements always start out looking like they're trying to
> deny this, which gets everybody up in arms, because this really
> *is* true.

Yes, it is true.

> Hmmm; this feels like a back-door way of coming at the problem, and
> also
> doesn't give me any help in minimzing noise -- both my cameras have
> a base ISO of 200, so I can't turn down the ISO in either case.

More sensitive area reduces noise at the same ISO when more photons are
captured, other things being equal.

> But one of them is a Nikon D700, and one is an Olympus E-PL2. I know
> which one is noisier at high ISO! It's the one with the smaller
> pixels,
> which in this case is the one with the smaller sensor. (They're also
> the
> same number of pixels, so that makes all sorts of comparisons easy.)
>
> Signal-to-noise ratio isn't a stated spec or anything we have a
> standard
> for measuring in cameras (that's widely used and understood, anyway).
>
> It's generally true that, for any given technology, smaller pixels
> will be
> noisier at ANY ISO (than larger pixels at that same ISO). Won't
> argue
> against that for a moment.

But a newer 4/3 sensor, one with higher quantum efficiency, might just
beat an older APS-C sensor. That's when all things /aren't/ equal.

> But despite having been around this course before, I still wasn't
> able to read that out of your initial statements. It'd maybe be good
> to work on how you present this issue, to avoid the initial confusion
> and opposition.

It takes time to think about these issues, as they are not initially
obvious.

Cheers,
David

 bob 06-14-2011 07:12 AM

Re: Should 4/3 lenses be half the size of full frame lenses?

To me, an 4/3 lense that is equivalent to a 35mm lense should have the same
maximum f number and angle of view.

This way, a 35mm camera and a 4/3 camera can shoot the same scene using the
same exposure (shutter speed and aperture) and end up with more or less
identical photos (except DOF, noise, and maybe resolution).

 David J Taylor 06-14-2011 09:02 AM

Re: Should 4/3 lenses be half the size of full frame lenses?

"bob" <nospam@hotmail.com> wrote in message
news:it71ko\$hl7\$1@speranza.aioe.org...
> To me, an 4/3 lense that is equivalent to a 35mm lense should have the
> same maximum f number and angle of view.
>
> This way, a 35mm camera and a 4/3 camera can shoot the same scene using
> the same exposure (shutter speed and aperture) and end up with more or
> less identical photos (except DOF, noise, and maybe resolution).

Yes, that's a perfectly fair way of looking at it - depending on your
definition of "identical"! Given that, why aren't the lenses half the
linear dimension, a quarter of the area, and an eighth of the weight,
particularly for micro-4/3 where back-focus requirements are less?

Cheers,
David

 Bruce 06-14-2011 06:11 PM

Re: Should 4/3 lenses be half the size of full frame lenses?

Paul Furman <paul-@-edgehill.net> wrote:
>Bruce wrote:
>> The light gathering power of an f/2.8 Four Thirds lens is identical to
>> an f/2.8 ...full frame lens

>
>With 1/4 the sensor size so 1/4 the print size.

That's only true if the Four Thirds sensor has a quarter as many
pixels as the full frame sensor.

If the number of pixels is the same, the print size will be the same
for the same ppi at the printing stage. All that matters at the
printing stage is the number of pixels. The printer has no idea
whether those pixels came from a P&S, Four Thirds, APS-C, full frame
or medium format.

 nospam 06-14-2011 08:15 PM

Re: Should 4/3 lenses be half the size of full frame lenses?

In article <ZuednRMDT7GrI2rQnZ2dnUVZ_gmdnZ2d@giganews.com>, Neil
Harrington <not@home.net> wrote:

> >> 4/3 camera has a sensor that is about half the length and height of a
> >> full frame sensor (1/4 the area).
> >>
> >> Does that mean a 4/3 camera lense would be half the diameter of an
> >> equivalent full frame lense?

> >
> > .. and half the length, and one eighth of the weight! Doesn't seem
> > to be so in practice, though. You also use the word "equivalent". To be
> > equivalent in light gathering power an f/2.8 full-frame lens
> > would need to be replaced by an f/1.4 half-frame lens. Somewhat more
> > costly to make, if possible at all.

>
> That makes no sense whatever.

yes it does.

> An f/2.8 lens is an f/2.8 lens, regardless of what format it's meant to
> cover. Its "light gathering power" is the same as any other lens of similar
> f-number as far as photographic purposes are concerned, disregarding
> differences in coating, etc.

it's light gathering power per unit area is the same (exposure) but a
larger sensor has a larger area so the total amount of light collected
is higher.

> Even if you were right about that light-gathering business you'd be wrong in
> your conclusion: a half-frame format does not have half the diagonal of full
> frame. (It's 30mm vs about 43mm.)

4/3rds is approximately 1/4 the area of full frame, or two stops, thus
an f/2.8 lens on full frame is equivalent to an f/1.4 lens on 4/3rds.

All times are GMT. The time now is 02:44 AM.