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OT: stops or EVs

 
 
Colin_D
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      01-24-2007
Charles Schuler wrote:
> I am teaching digital photography in my community and lean toward EVs as
> opposed to stops. I know that the two are equivalent, but I also know that
> they are not the same thing.
>
> My feeling is that f/stops or f-stops, technically speaking, should only
> refer only to the aperture of the lens. I fully understand that an
> equivalent exists by changing shutter speed or ISO or both. With all of the
> folks now entering digital photography as a hobby, it would be advantageous
> to clear this issue a bit.
>
> I also find that camera manuals lean towards EV.
>
> What are your thoughts?
>
>

My opinion is that teaching just EV won't be enough, but it depends on
what level of proficiency you are aiming at, and what sort of cameras
you students will be using.

EV is a simplification introduced to make it easier for non-photogs to
be able to use metered cameras without knowledge of aperture/shutter
interaction. At one time, some cameras used a mechanical coupling
between shutter and aperture marked with EV values to assist with this,
but I think those are now obsolete. If your students' cameras don't
have EV scales, I think it's pointless to teach exposure etc. from an EV
standpoint.

EV tells you nothing about the characteristics of stops/aperture. The
term 'stop' arose in the days before variable diaphragms were used.
Discs with various sized holes (Waterhouse stops, named after the
inventor, I guess) were placed in front of, or in a slot in the lens, to
control exposure and depth of field.

The major effects of varying the aperture need to be well understood by
students, from shallow depth to great depth of field, plus the effect on
some lens aberrations, the concept of diffraction limits and Airey Disc
definition limitations with very small apertures.

None of this fundamental knowledge is even hinted at by teaching EV alone.

Nor is the effect of shutter speed on subject movement, camera shake,
and reciprocity failure with film. Reciprocity is not a problem with
digital, but IMO if your students are to have a good grounding, they
should be aware if they find themselves using film. They may well
graduate to a MF or LF camera.

Colin D.

--
Posted via a free Usenet account from http://www.teranews.com

 
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Charles Schuler
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      01-24-2007

"Neil Ellwood" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> On Tue, 23 Jan 2007 17:45:48 -0500, Charles Schuler wrote:
>
>> I am teaching digital photography in my community and lean toward EVs as
>> opposed to stops. I know that the two are equivalent, but I also know
>> that
>> they are not the same thing.
>>
>> My feeling is that f/stops or f-stops, technically speaking, should only
>> refer only to the aperture of the lens. I fully understand that an
>> equivalent exists by changing shutter speed or ISO or both. With all of
>> the
>> folks now entering digital photography as a hobby, it would be
>> advantageous
>> to clear this issue a bit.
>>
>> I also find that camera manuals lean towards EV.
>>
>> What are your thoughts?

>
> If you are teaching photography - God help your students.


What is it with assholes like you? I think it was an interesting question,
but you had to respond with vitriol. **** off.


 
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J. Clarke
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Posts: n/a
 
      01-25-2007
On Thu, 25 Jan 2007 11:38:46 +1300, Colin_D <nospam@127.0.0.1> wrote:

>Charles Schuler wrote:
>> I am teaching digital photography in my community and lean toward EVs as
>> opposed to stops. I know that the two are equivalent, but I also know that
>> they are not the same thing.
>>
>> My feeling is that f/stops or f-stops, technically speaking, should only
>> refer only to the aperture of the lens. I fully understand that an
>> equivalent exists by changing shutter speed or ISO or both. With all of the
>> folks now entering digital photography as a hobby, it would be advantageous
>> to clear this issue a bit.
>>
>> I also find that camera manuals lean towards EV.
>>
>> What are your thoughts?
>>
>>

>My opinion is that teaching just EV won't be enough, but it depends on
>what level of proficiency you are aiming at, and what sort of cameras
>you students will be using.
>
>EV is a simplification introduced to make it easier for non-photogs to
>be able to use metered cameras without knowledge of aperture/shutter
>interaction. At one time, some cameras used a mechanical coupling
>between shutter and aperture marked with EV values to assist with this,
>but I think those are now obsolete. If your students' cameras don't
>have EV scales, I think it's pointless to teach exposure etc. from an EV
>standpoint.
>
>EV tells you nothing about the characteristics of stops/aperture. The
>term 'stop' arose in the days before variable diaphragms were used.
>Discs with various sized holes (Waterhouse stops, named after the
>inventor, I guess) were placed in front of, or in a slot in the lens, to
>control exposure and depth of field.
>
>The major effects of varying the aperture need to be well understood by
>students, from shallow depth to great depth of field, plus the effect on
>some lens aberrations, the concept of diffraction limits and Airey Disc
>definition limitations with very small apertures.
>
>None of this fundamental knowledge is even hinted at by teaching EV alone.
>
>Nor is the effect of shutter speed on subject movement, camera shake,
>and reciprocity failure with film. Reciprocity is not a problem with
>digital, but IMO if your students are to have a good grounding, they
>should be aware if they find themselves using film. They may well
>graduate to a MF or LF camera.


Seems to me that one should know aperture and shutter speed and EV as
well--I don't see it as "either/or".


 
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Gisle Hannemyr
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Posts: n/a
 
      01-25-2007
"Charles Schuler" <(E-Mail Removed)> writes:
> I am teaching digital photography in my community and lean toward
> EVs as opposed to stops. I know that the two are equivalent, but I
> also know that they are not the same thing.
>
> My feeling is that f/stops or f-stops, technically speaking, should
> only refer only to the aperture of the lens. I fully understand
> that an equivalent exists by changing shutter speed or ISO or both.
> With all of the folks now entering digital photography as a hobby,
> it would be advantageous to clear this issue a bit.
>
> I also find that camera manuals lean towards EV.
>
> What are your thoughts?


EV (or both). They are only equivalent in certain contexts.

Knowing about absolute EV as a specific quantity of light
(see: http://hannemyr.com/photo/ir.html#ev ) is important.
There is no sensible way to get this concept across using
stops.

Personally I also think that talking about various types of
exposure compensation, such as FEC, in terms of EV is much
more intutive than using stops. "Adjust your flash up two
stops" sounds strange in my ears, but "Dial in +2 EV on your
flash" makes sense.

All handheld spot meters, and many handheld average meters are
reporting light as EV, and I don't think that will change.
If they are going to learn how to use a manual light meter,
they need to understand EV.

If your students are going to learn advanced subjects, such as
the Zone System - http://hannemyr.com/photo/zonesystem.html -
they need to know avout EV.

So I think your instincts are right. EV is not obsolete and
photography students need to know about EV.

They also need to know that when one is talking about aperture
adjustments, EV and stops are equivalent, and that many people
use the term "stop" as a synonym for "EV" when discussing
halving our doubling the shutter speed or ISO. But EV is
used in so many contexts where "stop" will not do, that I think
that the best approach when teaching is to introduce it its
own right.
--
- gisle hannemyr [ gisle{at}hannemyr.no - http://hannemyr.com/photo/ ]
------------------------------------------------------------------------
Sigma SD10, Kodak DCS460, Canon Powershot G5, Olympus 2020Z
------------------------------------------------------------------------
 
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Colin_D
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Posts: n/a
 
      01-25-2007
J. Clarke wrote:
> On Thu, 25 Jan 2007 11:38:46 +1300, Colin_D <nospam@127.0.0.1> wrote:
>
>> Charles Schuler wrote:
>>> I am teaching digital photography in my community and lean toward EVs as
>>> opposed to stops. I know that the two are equivalent, but I also know that
>>> they are not the same thing.
>>>
>>> My feeling is that f/stops or f-stops, technically speaking, should only
>>> refer only to the aperture of the lens. I fully understand that an
>>> equivalent exists by changing shutter speed or ISO or both. With all of the
>>> folks now entering digital photography as a hobby, it would be advantageous
>>> to clear this issue a bit.
>>>
>>> I also find that camera manuals lean towards EV.
>>>
>>> What are your thoughts?
>>>
>>>

>> My opinion is that teaching just EV won't be enough, but it depends on
>> what level of proficiency you are aiming at, and what sort of cameras
>> you students will be using.
>>
>> EV is a simplification introduced to make it easier for non-photogs to
>> be able to use metered cameras without knowledge of aperture/shutter
>> interaction. At one time, some cameras used a mechanical coupling
>> between shutter and aperture marked with EV values to assist with this,
>> but I think those are now obsolete. If your students' cameras don't
>> have EV scales, I think it's pointless to teach exposure etc. from an EV
>> standpoint.
>>
>> EV tells you nothing about the characteristics of stops/aperture. The
>> term 'stop' arose in the days before variable diaphragms were used.
>> Discs with various sized holes (Waterhouse stops, named after the
>> inventor, I guess) were placed in front of, or in a slot in the lens, to
>> control exposure and depth of field.
>>
>> The major effects of varying the aperture need to be well understood by
>> students, from shallow depth to great depth of field, plus the effect on
>> some lens aberrations, the concept of diffraction limits and Airey Disc
>> definition limitations with very small apertures.
>>
>> None of this fundamental knowledge is even hinted at by teaching EV alone.
>>
>> Nor is the effect of shutter speed on subject movement, camera shake,
>> and reciprocity failure with film. Reciprocity is not a problem with
>> digital, but IMO if your students are to have a good grounding, they
>> should be aware if they find themselves using film. They may well
>> graduate to a MF or LF camera.

>
> Seems to me that one should know aperture and shutter speed and EV as
> well--I don't see it as "either/or".
>

Well, your in your OP you implied that you want to teach EV in
preference to stops, and that is what I and others have replied to.

Colin D.

--
Posted via a free Usenet account from http://www.teranews.com

 
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Paul Repacholi
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      01-27-2007
http://www.velocityreviews.com/forums/(E-Mail Removed) (Philip Homburg) writes:

> It depends on how you intend to use it. An EV is absolute value: it
> specifies a certain amount of light reaching the sensor. On the
> other hand, 'stops' are often used to specify a difference in
> exposure: "underexpose by 1 or 2 stops".


No, that is an LV. EV are shutter speed/f stop pairs that are only
equal to LVs if you are using 100asa film, or equivalent. Find an old
Rollie TLR or 'blad and play with the setting.

 
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Paul Repacholi
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Posts: n/a
 
      01-27-2007
Gisle Hannemyr <(E-Mail Removed)> writes:

> Knowing about absolute EV as a specific quantity of light
> (see: http://hannemyr.com/photo/ir.html#ev ) is important.


NO it is NOT! This is so far out, it is not even wrong! The
related number for light values is LV. EV is only a speed/f#
pairingand is not related at all to LV unless you specify
a film speed as well.

If you are going to teach it, get it 100% right, there is no excuse
not to.

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Philip Homburg
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      01-27-2007
In article <(E-Mail Removed)>,
Paul Repacholi <(E-Mail Removed)> wrote:
>(E-Mail Removed) (Philip Homburg) writes:
>
>> It depends on how you intend to use it. An EV is absolute value: it
>> specifies a certain amount of light reaching the sensor. On the
>> other hand, 'stops' are often used to specify a difference in
>> exposure: "underexpose by 1 or 2 stops".

>
>No, that is an LV. EV are shutter speed/f stop pairs that are only
>equal to LVs if you are using 100asa film, or equivalent. Find an old
>Rollie TLR or 'blad and play with the setting.


Yes, you are right. EV is more like the amount of light as a function
of the subject brightness.





--
That was it. Done. The faulty Monk was turned out into the desert where it
could believe what it liked, including the idea that it had been hard done
by. It was allowed to keep its horse, since horses were so cheap to make.
-- Douglas Adams in Dirk Gently's Holistic Detective Agency
 
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Charles Schuler
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      01-27-2007

"Charles Schuler" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed). ..
>I am teaching digital photography in my community and lean toward EVs as
>opposed to stops. I know that the two are equivalent, but I also know that
>they are not the same thing.
>
> My feeling is that f/stops or f-stops, technically speaking, should only
> refer only to the aperture of the lens. I fully understand that an
> equivalent exists by changing shutter speed or ISO or both. With all of
> the folks now entering digital photography as a hobby, it would be
> advantageous to clear this issue a bit.


I know that stops are different things than exposure values. My point
was/is about discussing changes: delta stops = delta EVs (a change of one
stop is equal to a change of one EV). One can achieve an exposure change by
varying aperture, shutter speed or ISO (or any combination). I like EV
because it is a more general concept and fits better with light meters, etc.

However, the common vernacular heavily favors stops. That doesn't mean it
is necessarily the best way to teach it.

Photography is not rocket science but it can be confusing for beginners.

Thanks to all who responded (well, mostly).


 
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King Sardon
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Posts: n/a
 
      01-27-2007
On Sat, 27 Jan 2007 16:18:08 -0500, "Charles Schuler"
<(E-Mail Removed)> wrote:

>
>"Charles Schuler" <(E-Mail Removed)> wrote in message
>news:(E-Mail Removed) ...
>>I am teaching digital photography in my community and lean toward EVs as
>>opposed to stops. I know that the two are equivalent, but I also know that
>>they are not the same thing.
>>
>> My feeling is that f/stops or f-stops, technically speaking, should only
>> refer only to the aperture of the lens. I fully understand that an
>> equivalent exists by changing shutter speed or ISO or both. With all of
>> the folks now entering digital photography as a hobby, it would be
>> advantageous to clear this issue a bit.

>
>I know that stops are different things than exposure values. My point
>was/is about discussing changes: delta stops = delta EVs (a change of one
>stop is equal to a change of one EV). One can achieve an exposure change by
>varying aperture, shutter speed or ISO (or any combination). I like EV
>because it is a more general concept and fits better with light meters, etc.
>
>However, the common vernacular heavily favors stops. That doesn't mean it
>is necessarily the best way to teach it.


IIRC, a "stop" was originally (in the real old days) a small opaque
plate with a hole in it of a particular size that was inserted
transversely into a lens to control the amount of light. The stop
wasn't the aperture, it was the opaque part. And the different hole
sizes usually didn't vary by factors of 2.

So today's meaning of stop = 2-fold change in aperture cross-sectional
area isn't really accurate either.

KS
 
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