Why do m4/3 shooters feel threated so by "Equivalence" ???

bobn2 said:

DickyUK said:

Apertures allow the same amount of light through no matter what format you use

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but the amount of light the film or sensor collects depends on how big it is.

--
Bob

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Yes. At first I couldn't understand the benefit, until I thought of radio antennas. If an antenna is 4x the length of another of the same design, it will receive a stronger signal compared to noise (static) much as a larger sensor would receive in the same manner. It may be that the sensors and processors are getting so good in general, that for practical purposes the difference is not noticed as much as in the past?
--



http://www.pbase.com/madlights
http://barriolson.aminus3.com/
"why so serious?": The Joker

zakk9 said:

Oh, and btw.; there is no equivalence, except in some textbooks. It becomes very apparent when shooting medium format and above. The equivalent focal length and aperture still gives a different look. Buy an old MF camera and some film and have a look yourself.

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All comparisons between systems that are based on geometry and ratios will of course be inaccurate to some extent. If the systems have similar sensor sizes (or film size) then the theory will accord better with reality.

Nobody should ever buy something based on the capability of something else and an "equivalence" theory. Just because a lens of a given relative aperture and focal length for one system yields a certain result does not imply that an "equivalent in angle of view and DOF" lens will yield the same -- or even a very similar -- result.

Reality always trumps theory, especially if the theory is of necessity very simple.

boggis the cat said:

bobn2 said:

DickyUK said:

Apertures allow the same amount of light through no matter what format you use

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but the amount of light the film or sensor collects depends on how big it is.

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This is precisely why it is incorrect to change an f-number (relative aperture) of a lens based on a sensor size comparison.

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It's also incorrect to change a focal length. However, just as the effect of the focal length changes as a function of format, the effect of the f-ratio changes in the same proportion.

boggis the cat said:

All of the various differences in effect and capability* between systems can be derived from knowing the sensor areas and the respective lens f-numbers and focal lengths.

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Indeed. The sensor ratio (more commonly called the "crop factor") is typically calculated as the ratio of the sensor diagonals, and, when applied to the focal length of the lens, give the equivalent focal length, and when applied to the f-ratio, gives the equivalent f-ratio.

boggis the cat said:

Transformational specifications, such as "EFL" and the suggested "Ef", should serve to make comparisons easier and prevent confusion.

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I like to say that 25mm f/2 on 4/3 (mFT) is equivalent to 50mm f/4 on FF. By "equivalent to", I mean that it results in the same DOF (and diffraction softening) for a given perspective, AOV, and display size. It results in the same total light falling on the sensor for a given shutter speed (usually attained by upping the ISO two stops on FF). The same total light falling on the sensor results in the same noise if the sensors are equally efficient (less noise if the sensor is more efficient, more noise if the sensor is less efficient).

If you prefer to say 25mm on 4/3 (mFT) has an EFL of 50mm on FF, and f/2 on 4/3 (mFT) is Ef/4 on FF, I have no objection whatsoever. After all, the "E" in "EFL" and "Ef" means "equivalent", which is the exact same thing I've been saying.

boggis the cat said:

[* At least theoretical capability; or to a first approximation. It would be foolish to purchase a system or choose a lens based solely on a theoretical comparison.]

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But of course.

Great Bustard said:

If you are going to argue that you can't use the term "equivalent" because noise equivalence only holds for equally efficient sensors, then you can't say that the 75 / 1.8 on an EM5 is equivalent to the same 75 / 1.8 on an EPL1, which, of course, is nonsense.

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It is nonsense because what creates the change in effects is the sensors . The lens remains the same.

Similarly, putting a 135 format lens on a 135 sensor body or an APS-C sensor body does not change the lens at all. It is always the sensors involved in any form of "equivalence", whether it be angle of view or DOF or noise. Your "equivalent photographs" argument discards all sensor behaviour aside from the ratio of areas for the sake of simplicity.

By your full "equivalence" argument, for which you must include raising ISO, the same 75 mm f/1.8 lens placed on an E-M5 or E-PL1 have different "equivalences" to a functionally equivalent lens on a 135 sensor system. (And the same would apply if you keep the same body and lens combination on mFT but replace the 135 format body behind the same lens.)

boggis the cat said:

Great Bustard said:

If you are going to argue that you can't use the term "equivalent" because noise equivalence only holds for equally efficient sensors, then you can't say that the 75 / 1.8 on an EM5 is equivalent to the same 75 / 1.8 on an EPL1, which, of course, is nonsense.

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It is nonsense because what creates the change in effects is the sensors . The lens remains the same.

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I believe I have always said that. Here, let me quote that for you for the thousandth time:

josephjamesphotography.com/equivalence/#quick

• Neither the focal length nor the f-ratio of a lens change as a function of format: 50mm = 50mm and f/2 = f/2 regardless of the format the lens is used on.

boggis the cat said:

Your "equivalent photographs" argument discards all sensor behaviour aside from the ratio of areas for the sake of simplicity.

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Do tell. What, exactly, is my "equivalent photographs argument"? Link and quote, or paraphrase from memory. I'll correct any errors, as needed.

boggis the cat said:

By your full "equivalence" argument, for which you must include raising ISO...

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Actually, you don't (that's a whole other discussion), but, for sure, it's the usual way about it.

boggis the cat said:

...the same 75 mm f/1.8 lens placed on an E-M5 or E-PL1 have different "equivalences" to a functionally equivalent lens on a 135 sensor system. (And the same would apply if you keep the same body and lens combination on mFT but replace the 135 format body behind the same lens.)

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You'll have to say that more clearly. I say a 75mm f/1.8 on mFT is equivalent to 150mm f/3.6 on FF, where by "equivalent to", I mean that it results in the same DOF (and diffraction softening) for a given perspective, AOV, and display size. It results in the same total light falling on the sensor for a given shutter speed (usually attained by upping the ISO two stops on FF). The same total light falling on the sensor results in the same noise if the sensors are equally efficient (less noise if the sensor is more efficient, more noise if the sensor is less efficient).

You may have seen me post that once or twice.

Great Bustard said:

boggis the cat said:

This is precisely why it is incorrect to change an f-number (relative aperture) of a lens based on a sensor size comparison.

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It's also incorrect to change a focal length. However, just as the effect of the focal length changes as a function of format, the effect of the f-ratio changes in the same proportion.

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The difference is that we all know the conventional use of focal length as a proxy for angle of view.

Nobody would be confused into thinking that a 75 mm f/2 lens described as 150 mm EFL f/2 had a larger aperture. Nor are they likely to be confused by a statement such as "75 mm f/2 on mFT is equivalent to 150 mm f/2 on 135", even though it is technically incorrect.

Change the relative apertures without explanation, however, and you create confusion and arguments.

Great Bustard said:

Great Bustard said:

All of the various differences in effect and capability* between systems can be derived from knowing the sensor areas and the respective lens f-numbers and focal lengths.

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Indeed. The sensor ratio (more commonly called the "crop factor")

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Or "uncrop factor", presumably, if considering a sensor larger than 135?

Great Bustard said:

is typically calculated as the ratio of the sensor diagonals,

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That is problematic when you have different aspect ratios. The same diagonal at e.g. 16:9 will capture a lot less light than at 1:1.

Relative apertures would be calculated based on the native aspect ratio.

Great Bustard said:

and, when applied to the focal length of the lens, give the equivalent focal length, and when applied to the f-ratio, gives the equivalent f-ratio.

Great Bustard said:

Transformational specifications, such as "EFL" and the suggested "Ef", should serve to make comparisons easier and prevent confusion.

Click to expand...

I like to say that 25mm f/2 on 4/3 (mFT) is equivalent to 50mm f/4 on FF. By "equivalent to", I mean that it results in the same DOF (and diffraction softening) for a given perspective, AOV, and display size.

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The problem is that unless you state that you will create confusion. Using a clear convention is better than pretending that "equivalent" has a specific narrow meaning.

Great Bustard said:

It results in the same total light falling on the sensor for a given shutter speed (usually attained by upping the ISO two stops on FF). The same total light falling on the sensor results in the same noise if the sensors are equally efficient (less noise if the sensor is more efficient, more noise if the sensor is less efficient).

If you prefer to say 25mm on 4/3 (mFT) has an EFL of 50mm on FF, and f/2 on 4/3 (mFT) is Ef/4 on FF, I have no objection whatsoever.

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Complete constructions are also clear:

• 25 mm f/2 on mFT is 50 mm EFL f/2
• 25 mm f/2 on mFT is 25 mm Ef/4
• 25 mm f/2 on mFT is 50 mm EFL Ef/4

Possible short-forms could be used:

• 25/2 on mFT is E50/2
• 25/2 on mFT is 25/E4
• 25/2 on mFT is E50/E4
• 25/2 on mFT is E(50/4)

The last two above are your "equivalent photographs", but the second option seems clearer.

Great Bustard said:

After all, the "E" in "EFL" and "Ef" means "equivalent", which is the exact same thing I've been saying.

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You'll find both "equivalent focal length" and "effective focal length" being used interchangeably. It is the effect that is being considered when making all of these transforms.

Great Bustard said:

It's also incorrect to change a focal length. However, just as the effect of the focal length changes as a function of format, the effect of the f-ratio changes in the same proportion.

Great Bustard said:

All of the various differences in effect and capability* between systems can be derived from knowing the sensor areas and the respective lens f-numbers and focal lengths.

Click to expand...

Indeed. The sensor ratio (more commonly called the "crop factor") is typically calculated as the ratio of the sensor diagonals, and, when applied to the focal length of the lens, give the equivalent focal length, and when applied to the f-ratio, gives the equivalent f-ratio.

Great Bustard said:

Transformational specifications, such as "EFL" and the suggested "Ef", should serve to make comparisons easier and prevent confusion.

Click to expand...

I like to say that 25mm f/2 on 4/3 (mFT) is equivalent to 50mm f/4 on FF. By "equivalent to", I mean that it results in the same DOF (and diffraction softening) for a given perspective, AOV, and display size.

Click to expand...

the results change, the lens nor its aperture do not change at all

Great Bustard said:

It results in the same total light falling on the sensor for a given shutter speed (usually attained by upping the ISO two stops on FF).

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sham really, if there was more light the exposure would have to adjust, but the exposure will be the same at the same shutter, aperture and ISO.

jacking the ISO 2 stops doesnt mean you have more light, it just means that having stopped down 2 stops (decreasing light) you have to adjust the ISO to get the same exposure, you did that because the net light is the same. TL=BS

the light, like the aperture in the previous example, is the same

what do you think would happen if you used the same lens on both systems, with the camera settings, ISO, shutter and aperture set the same. In the case of mFT you made 4 frames, 2 up and 2 down, that you stitched together to make one complete pano roughly the dimensions of the FF example.

I would want to know if they looked very similar
I would want to know why the same settings worked if FF had more TLight,
I would want to know how the bokeh/separation compared.

--
Riley

any similarity to persons living or dead is coincidental and unintended
support 1022 Sunday Scapes'

boggis the cat said:

bobn2 said:

DickyUK said:

Apertures allow the same amount of light through no matter what format you use

Click to expand...

but the amount of light the film or sensor collects depends on how big it is.

Click to expand...

This is precisely why it is incorrect to change an f-number (relative aperture) of a lens based on a sensor size comparison.

Click to expand...

No-one proposes changing the f-number if a lens based on a sensor size comparison.

boggis the cat said:

All of the various differences in effect and capability* between systems can be derived from knowing the sensor areas and the respective lens f-numbers and focal lengths.

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They can, but it's simpler and easier just to apply the crop factor to the f-number to find out how a lens of the same AOV works on the different format. Your argument applies just as much to the FL - you can work out how things work by knowing the actual focal length and the sensor size, but multiplying the FL by the crop factor is a useful convenience, and many people use it.

boggis the cat said:

Transformational specifications, such as "EFL" and the suggested "Ef", should serve to make comparisons easier and prevent confusion.

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As has been said, you can use the notation you like, I can't see a situation where your 'transformational specifications' help - because the problem by and large is not 'confusion', it is wilful ignorance.

--
Bob

boggis the cat said:

boggis the cat said:

I like to say that 25mm f/2 on 4/3 (mFT) is equivalent to 50mm f/4 on FF. By "equivalent to", I mean that it results in the same DOF (and diffraction softening) for a given perspective, AOV, and display size. It results in the same total light falling on the sensor for a given shutter speed (usually attained by upping the ISO two stops on FF). The same total light falling on the sensor results in the same noise if the sensors are equally efficient (less noise if the sensor is more efficient, more noise if the sensor is less efficient).

Click to expand...

Click to expand...

boggis the cat said:

The problem is that unless you state that you will create confusion. Using a clear convention is better than pretending that "equivalent" has a specific narrow meaning.

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I use a term. I italicize it. I immediately define what is meant by the term. Honestly, who would be confused by that (rhetorical question).

boggis the cat said:

boggis the cat said:

If you prefer to say 25mm on 4/3 (mFT) has an EFL of 50mm on FF, and f/2 on 4/3 (mFT) is Ef/4 on FF, I have no objection whatsoever.

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Complete constructions are also clear:

• 25 mm f/2 on mFT is 50 mm EFL f/2
• 25 mm f/2 on mFT is 25 mm Ef/4
• 25 mm f/2 on mFT is 50 mm EFL Ef/4

Possible short-forms could be used:

• 25/2 on mFT is E50/2
• 25/2 on mFT is 25/E4
• 25/2 on mFT is E50/E4
• 25/2 on mFT is E(50/4)

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In not one, not one of those, did you define your terminology, whereas I did. And you accuse me of not being clear? Wow. Now you know why our "discussions" go the way they do.

boggis the cat said:

boggis the cat said:

After all, the "E" in "EFL" and "Ef" means "equivalent", which is the exact same thing I've been saying.

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You'll find both "equivalent focal length" and "effective focal length" being used interchangeably. It is the effect that is being considered when making all of these transforms.

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"Equivalent" or "Effective" -- don't care. They mean the same thing in this context.

by all means, take your time girls

[edit]

well I can see you have worked your stuff out so well you are busy PM'ing each other for the answer you dont want to give

in the meantime I'm outa here as I have stuff to do
like as not I wont be back in time for the corrective answer it will surely need

--
Riley

any similarity to persons living or dead is coincidental and unintended
support 1022 Sunday Scapes'

Rriley said:

Great Bustard said:

It's also incorrect to change a focal length. However, just as the effect of the focal length changes as a function of format, the effect of the f-ratio changes in the same proportion.

Rriley said:

All of the various differences in effect and capability* between systems can be derived from knowing the sensor areas and the respective lens f-numbers and focal lengths.

Click to expand...

Indeed. The sensor ratio (more commonly called the "crop factor") is typically calculated as the ratio of the sensor diagonals, and, when applied to the focal length of the lens, give the equivalent focal length, and when applied to the f-ratio, gives the equivalent f-ratio.

Rriley said:

Transformational specifications, such as "EFL" and the suggested "Ef", should serve to make comparisons easier and prevent confusion.

Click to expand...

I like to say that 25mm f/2 on 4/3 (mFT) is equivalent to 50mm f/4 on FF. By "equivalent to", I mean that it results in the same DOF (and diffraction softening) for a given perspective, AOV, and display size.

Click to expand...

the results change, the lens nor its aperture do not change at all

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Let me see, have I said (read) something like that before. Let me see. Oh yes, here it is:

josephjamesphotography.com/equivalence/#quick

• Neither the focal length nor the f-ratio of a lens change as a function of format: 50mm = 50mm and f/2 = f/2 regardless of the format the lens is used on.

• The effect of the focal length and f-ratio of a lens, however, do change as a function of format.

I wonder how many times that's been pointed out to you.

Rriley said:

Rriley said:

It results in the same total light falling on the sensor for a given shutter speed (usually attained by upping the ISO two stops on FF).

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sham really, if there was more light the exposure would have to adjust, but the exposure will be the same at the same shutter, aperture and ISO.

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The exposure is a function of the scene luminance, t-stop (closely approximated by the f-ratio), and shutter speed. The role of ISO is simply in the brightness of the photo.

Rriley said:

jacking the ISO 2 stops doesnt mean you have more light, it just means that having stopped down 2 stops (decreasing light) you have to adjust the ISO to get the same exposure, you did that because the net light is the same. TL=BS

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Your ignorance comes through once again. Changing the ISO has no effect on the amount of light falling on the sensor for a given scene luminance, f-ratio, and shutter speed. It's simply an affect of processing for the image brightness.

Rriley said:

the light, like the aperture in the previous example, is the same

what do you think would happen if you used the same lens on both systems, with the camera settings, ISO, shutter and aperture set the same. In the case of mFT you made 4 frames, 2 up and 2 down, that you stitched together to make one complete pano roughly the dimensions of the FF example.

I would want to know if they looked very similar
I would want to know why the same settings worked if FF had more TLight,
I would want to know how the bokeh/separation compared.

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Why would anyone compare two different formats with the same lens? As has been posed to you several times before, but with no answer save "answers are voluntary, not compulsory", what does 50mm f/2 1/100 ISO 200 on mFT do for you, in terms of the visual properties of the final photo that 100mm f/4 1/100 ISO 800 on FF does not?

Does the answer have anything to do with the fact that f/2 on 4/3 (mFT) is equivalent tof/4 on FF where, byy "equivalent to", I mean that it results in the same DOF (and diffraction softening) for a given perspective, AOV, and display size. It results in the same total light falling on the sensor for a given shutter speed (usually attained by upping the ISO two stops on FF). The same total light falling on the sensor results in the same noise if the sensors are equally efficient (less noise if the sensor is more efficient, more noise if the sensor is less efficient).

Rriley said:

by all means, take your time girls
in the meantime I'm outa here as I have stuff to do
like as not I wont be back in time for the corrective answer it will surely need

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Oh, Riley, what will us girls do without your steady hands on the ship's wheel ? Abandon ship !

Once again - 150 posts on the horizon and still no evidence that any of this makes sense in the 'real' world.

Most m4/3 shooters are not threatened by equivalence . If you look at the threads, they are usually dominated by a couple of posters on both sides equally ardently sticking to their guns.

I would suggest that best practice regarding a comparison of lenses between sensors is to be very clear about under what circumstances you are comparing them. If you a merely looking for lenses that have the same angle of view, or if you are looking for lenses that provide the same depth of field, too. This should remove most opportunities of misunderstanding or accusations of misleading comparisons.

The issue of total light gathering and subsequent shot noise is a central bone of contention, but to me it is of secondary concern compared to angle of view and depth of field, and any possible noise inequivalence tends toward the insignificant when AoV and DoF are kept constant anyway.

While I agree that these massive threads can be tedious, I have to say that I'm disappointed with the attempts at character assassination that as far as I can see is mainly targetted at the equivalency proponents. I understand that there is some bad blood from old fights, but that doesn't excuse it.

Macx said:

Most m4/3 shooters are not threatened by equivalence . If you look at the threads, they are usually dominated by a couple of posters on both sides equally ardently sticking to their guns.

I would suggest that best practice regarding a comparison of lenses between sensors is to be very clear about under what circumstances you are comparing them. If you a merely looking for lenses that have the same angle of view, or if you are looking for lenses that provide the same depth of field, too. This should remove most opportunities of misunderstanding or accusations of misleading comparisons.

The issue of total light gathering and subsequent shot noise is a central bone of contention, but to me it is of secondary concern compared to angle of view and depth of field, and any possible noise inequivalence tends toward the insignificant when AoV and DoF are kept constant anyway.

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In my opinion, this sums up the whole deal:

50mm f/2 on 4/3 (mFT) is equivalent to 100mm f/4 on FF.

By "equivalent to", I mean that it results in the same AOV and aperture (entrance pupil) diameter 50mm / 2 = 100mm / 4 = 25mm).

The same perspective (subject-camera distance), AOV, and aperture diameter results in the same DOF (and diffraction softening).

The same aperture diameter and shutter speed (usually attained by upping the ISO two stops on FF) results in the same total light falling on the sensor.

The same total light falling on the sensor results in the same noise if the sensors are equally efficient (less noise if the sensor is more efficient, more noise if the sensor is less efficient).

Macx said:

While I agree that these massive threads can be tedious, I have to say that I'm disappointed with the attempts at character assassination that as far as I can see is mainly targetted at the equivalency proponents. I understand that there is some bad blood from old fights, but that doesn't excuse it.

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I like how Anders characterized it upthread:

http://forums.dpreview.com/forums/read.asp?forum=1041&message=41726748

Great Bustard said:

I tend to compare the "quality" of lenses at the same AOV and DOF. I can't quite find the sense in comparing wide open when the DOFs are different, just like I can't quite find the sense in comparin UWA to telephoto.

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Nevertheless, you just did. You said the FF 24/1.4s had more DoF control and more light-gathering ability. Now how can you say that if you insist that DoF must always be kept constant for comparison.

Great Bustard said:

Oh dear -- did you just say there's not enough blur?

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You bet ya'! You should have used your MF camera with 50/1.4 for this. Or taken a few steps backwards into that arcade right behind you and put on your 150/3.6.

Great Bustard said:

Myself, I don't know the history. I imagine, just as now, there were people who liked shallow DOF, and people who didn't, and what constituted "too shallow" was subjective.

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In all likelihood you are right. There are always individual exceptions no matter what the predominant thought patterns are like. The issue here what was à la mode and not, and that's different for sure.