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On 15/06/2011 1:02 PM, nospam wrote:
> In article<4df7f5d7$0$13391$ m.au>, dj_nme
> <> wrote:
>
>> The problem with your idea is that to get the same DoF and shutter speed
>> on a smaller format, the ISO must be lowered.
>> This is not always possible, EG: how do you lower the ISO if the setting
>> is already at the lowest when using the same aperture and shutter
>> setting as the FF camera?
>> Big problem, isn't it?
>
> nope. you raise the iso of the larger format.

Yes it is.

I am asking you how a smaller format could lower it's ISO when you have
opened up the aperture to match the exposure value of a FF camera set at
the same ISO.
If you don't know how, then just say so.

I know how to get around the problem (assuming that the smaller format
lens can open wide enough to match DoF): use ND filters to cut the
amount of light and prevent over-exposure (keeping the same exposure
value as on the FF camera).
Without the ND filters, you smaller format can't do that and you are SOL
(so out of luck).

On 15/06/2011 1:02 PM, nospam wrote:
> In article<4df7fb68$0$2447$ .au>, dj_nme
> <> wrote:
>
>>>>>> "equivalent f-stop" is using a aperture (f-stop) setting that gives an
>>>>>> equivalent DoF to 35mm at their 35mm EFL, not the same exposure value at
>>>>>> the same shutter speed.
>>>>>
>>>>> right, which for 4/3rds, is 2 stops wider.
>>>>
>>>> For the same DoF, not exposure value.
>>>
>>> which means to be equivalent, it must be 2 stops wider.
>>
>> So, how do you set the ISO lower than the lowest setting on the camera
>> to maintain the same exposure value?
>> It can't be done.
>
> raise the iso of the larger format.

That isn't what I was asking you.
I am asking how you would make the 4/3 camera match the FF camera.
Not the other way around.

>> Likewise, when an FF lens is set to f/1.4 there is no way that any 4/3
>> lens aperture could be opened wide enough to match DoF.
>> Where are the f/0.8 4/3 lenses?
>
> exactly why 4/3rds is limiting.

So this is all just sort of long, drawn-out 4/3 camera bash?
It would have been a whole more concise and not be wasting any-one
else's time.
You first post in in this thread should have been "4/3 cameras are
****!" and been done with it.

"dj_nme" <> wrote in message
news:4df86489$0$3032$ ...
[]
> So this is all just sort of long, drawn-out 4/3 camera bash?

It's a discussion of what is the "equivalent" lens for 4/3 compared to
full-frame, the question I asked in the first place. If you want
equivalent exposure times for a given light level, then look for the same
f/number. If you want equivalence in other areas such as the same
depth-of-focus or the same image quality for a given light level, you need
double the aperture, half the f/number.

Statements of physics as applied to different sensor sizes.

Cheers,
David

On 15/06/2011 6:32 PM, David J Taylor wrote:
> "dj_nme" <> wrote in message
> news:4df86489$0$3032$ ...
> []
>> So this is all just sort of long, drawn-out 4/3 camera bash?
>
> It's a discussion of what is the "equivalent" lens for 4/3 compared to
> full-frame, the question I asked in the first place. If you want
> equivalent exposure times for a given light level, then look for the
> same f/number. If you want equivalence in other areas such as the same
> depth-of-focus or the same image quality for a given light level, you
> need double the aperture, half the f/number.

I know all this, I have been participating in the discussion here.
Perhaps my reply to "nospam" should have been worded to make it clear
that I was after his solution (by writing "I am asking how would you
[nospam] make..."), rather than making it so open sounding.
I know how to get around the problem: ND filters.
It ain't rocket surgery.

> Statements of physics as applied to different sensor sizes.
>
> Cheers,
> David

It's just that nospam seems to want to turn it into an obtuse 4/3 format
bashing exercise.

RichA <> wrote:
>On Jun 13, 11:48*am, "bob" <nos...@hotmail.com> 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?
>
>Lets say you want a 300mm f2.8 lens. Now tell us how you make the end
>of it 50 or so mm's wide?
>http://www.digital-photography-schoo...-magnification


What you have missed, Rich, is that the equivalent Four Thirds lens
would be a 150mm f/2.8. In this case "equivalent" means "same angle
of view".

Olympus has made some truly stunning lenses for Four Thirds including:
150mm f/2 (300mm f/2 equivalent)
14-35mm f/2 (28-70mm f/2 equivalent)
35-100mm f/2 (70-200mm f/2 equivalent)
90-250mm f/2.8 (180-500mm f/2.8 equivalent)
300mm f/2.8 (600mm f/2.8 equivalent).

I have used the first and third of these.

All these Zuiko Digital lenses give superlative performance. Sadly,
due to the failure of the E System, they are not widely used.

In article <4df862ec$0$2442$>, dj_nme
<> wrote:

> I am asking you how a smaller format could lower it's ISO when you have
> opened up the aperture to match the exposure value of a FF camera set at
> the same ISO.
> If you don't know how, then just say so.

if you can't lower the iso on the 4/3rds you raise it on the full
frame. it doesn't matter which (or even a little on both), as long as
there's a 2 stop difference. it's really quite simple.

In article <4df86489$0$3032$>, dj_nme
<> wrote:

> >>>>> right, which for 4/3rds, is 2 stops wider.
> >>>>
> >>>> For the same DoF, not exposure value.
> >>>
> >>> which means to be equivalent, it must be 2 stops wider.
> >>
> >> So, how do you set the ISO lower than the lowest setting on the camera
> >> to maintain the same exposure value?
> >> It can't be done.
> >
> > raise the iso of the larger format.
>
> That isn't what I was asking you.
> I am asking how you would make the 4/3 camera match the FF camera.
> Not the other way around.

the ff camera has less noise than the 4/3rds camera (basic physics) so
to match it, you raise the iso of the larger sensor. very simple.

> >> Likewise, when an FF lens is set to f/1.4 there is no way that any 4/3
> >> lens aperture could be opened wide enough to match DoF.
> >> Where are the f/0.8 4/3 lenses?
> >
> > exactly why 4/3rds is limiting.
>
> So this is all just sort of long, drawn-out 4/3 camera bash?

it's not a bashing of anything.

> It would have been a whole more concise and not be wasting any-one
> else's time.
> You first post in in this thread should have been "4/3 cameras are
> ****!" and been done with it.

except that's not what this is all about.

On Jun 15, 2:30*am, "David J Taylor" <david-
tay...@blueyonder.co.uk.invalid> wrote:
> "J. Clarke" <jclarkeuse...@cox.net> wrote in message
>
> news: n.local...
> []
>
> > You're missing something here. *What matters is not the number of
> > photons passing through the lens, but the number that both pass through
> > the lens and strike the sensor. *The ones that pass through the image
> > circle but do not strike the sensor do not count.
>
> Agreed.
>
> > So the crucial figure is not the total number of photons passing through
> > the lens but the photons per unit area in the image plane.
>
> Photons per unit area is what affects the exposure required, but the total
> photons in the image is what affects total image quality.

Well, I don't want to try to speak for "all photographers",
because that's "always" a losing proposition. But I see
that I'm far from the only person who has trouble
understanding the way you explain this.

I think I understand what you're trying to convey now, and
it's true. But what you say above simply does not convey
it to me.

It may make perfect sense to people whose primary
photographic experience is with astronomical photography; I
don't know, since I've never done that. It's wrong,
misleading, sends people off into crazy land, if they think
like photographers.

It's also just plain false if taken literally -- a high-key
image will have more photons hitting the sensor total than
a low-key image, but that doesn't mean high-key images
inherently have higher image quality! But a literal
reading of "the total photons in the image is what affects
total image quality" says it does.

Noise level is inversely proportional to number of photons
hitting a pixel (sensel). All technological variables
being equal, bigger pixels produce lower noise. The sensor
size is irrelevant technologically; it's the pixel size
that matters.

As a marketing decision, most camera sensors (for sale new
at a given point in time) have roughly the same number of
pixels on them; when that is true, then pixel size tends to
relate to sensor size. But that's not a technological
rule, it's just a current marketing principle.

So; the choice of a modest-size-sensor camera like my
Olympus E-PL2 at 12MP is inherently accepting a higher
noise level at any given ISO than with a larger-sensor
camera of the same pixel count and vaguely similar
technology like my Nikon D700 (also 12MP, full 35mm frame).
True.

If I'm running my Nikon D700 above base ISO, I may be able
to match its noise level on the E-PL2 by selecting a lower
ISO. Doing this this will necessitate either a wider
aperture or a longer shutter speed. True. (This isn't
very useful to me in practice, because for an awful lot of
photos where noise matters a whole lot, I'm running the
D700 at base ISO to begin with; the E-PL2 has the same base
ISO, so I can't run it at a lower ISO in an attempt to
match the noise. The rest of the time, I'm running at the
widest aperture I have and the slowest shutter speed the
subject motion will allow, and using whatever ISO is needed
to make that work out; again, no room for opening up any
apertures or reducing the ISO.)

A 6MP E-PL2 would be a lot more valuable to me than the
12MP one they actually make! But apparently I'm not normal
(I've kind of gotten used to that over the years).

On Jun 15, 6:47*am, Bruce <docnews2...@gmail.com> wrote:

> Olympus has made some truly stunning lenses for Four Thirds including:
> 150mm f/2 (300mm f/2 equivalent)
> 14-35mm f/2 (28-70mm f/2 equivalent)
> 35-100mm f/2 (70-200mm f/2 equivalent)
> 90-250mm f/2.8 (180-500mm f/2.8 equivalent)
> 300mm f/2.8 (600mm f/2.8 equivalent).
>
> I have used the first and third of these.

Lucky dog .

> All these Zuiko Digital lenses give superlative performance. Sadly,
> due to the failure of the E System, they are not widely used.

And they're all for 4/3, not Micro 4/3, right? (The adapter looks
relatively expensive, but if I were buying those lenses, that would
just be noise.)

In theory, the smaller sensor would make it easier to design and build
such lenses. 35mm vs. medium format shows that in practice, as does
Super-8 vs. 16mm over in motion picture film (or I guess 16mm
vs. 35mm, but I've never worked with 35mm motion picture gear). I'm
sad only Olympus has taken much advantage of it.

And since my E-PL2 is my "toy camera", the small one that lives in my
shoulder bag all the time (with the Panasonic 20/1.7 pancake lens, so
it's just about 1/8" thicker than an LX3), I'm not investing that kind
of money in lenses for it (or carrying that kind of weight).

"Neil Harrington" <> wrote in message
news: ...
[]
> While you're correct WRT "light gathering power" as the term is
> generally used in astronomical telescopes, that isn't something that
> photographers are usually concerned with. You seem to be saying that
> f/1.4 on the smaller format would somehow be equivalent to f/2.8 on the
> larger, which is obviously not true.

Except in terms of light gathering power, and possibly other aspects such
as depth of field (but I've not done those sums).

[]
> "Half frame" is generally taken to mean 18 x 24 mm, or one-half the area
> of "full frame" whereas Four Thirds is about one-fourth. You are not
> correct in using "half frame" and "Four Thirds" to mean the same thing,
> which is what you seem to be doing.

Half of 36 x 24mm is 18 x 12mm, approximately the size of the four-thirds
frame (in area). Approximately on quarter of the area, yes. I was not
using "half frame" in any specialised meaning, so sorry for any confusion.

Cheers,
David