And the point you are making is still misinformation.
I disagree
And in doing so, you've written at least 6 more pieces of misinformation.
At macro distances, depth of field depends on effective aperture, not physical aperture.
We agree on this - but see point 7 below.
Clearly not, since you've claimed otherwise in the past and here you've demonstrated you clearly don't understand what either effective aperture or pupil magnification is.
What we do not agree on is whether when a lens like the 105 macro G at 1:1 using the command dial to set the aperture to report f4.8, f8 etc, shoots at a wider aperture.
Misinformed statement #1. We agree if it may shoot at a wider
Physical aperture. But it shoots at the same
effective aperture.
2/ Although the thread is primarily about the 105 macro G, the 60mm D in your profile works in a similar way to the 105 when setting the aperture via the command dial.
At 1:1 the 60mm f/2.8D has an effective aperture of f/5, whether you set an aperture of f/5 via the command dial, or you set an aperture of f/2.8 via the aperture ring. If you set f/8 via the aperture ring, you use a smaller effective aperture than if you set f/8 via the command dial. This is consistent with what I've written.
3/ If you set aperture via the command dial on your 60mm D at any aperture other than wide open (see below) with an evenly illuminated subject, the shutter blind closed or covered (for maximum exposure accuracy) and rotate the focus ring from infinity to 1:1 the exposure time does not increase by the 2 stops equivalent of a symmetrical macro.
As stated many times, that's because when you use the command dial, the camera chooses an effective aperture and selects the physical aperture which yields that effective aperture. Exposure, like depth of field, is controlled by effective aperture.
If the 60mm D was a symmetrical design lens (it is not) using command dial aperture priority at f8 read-out the exposure time should increase from (as an example) 1/60 at infinity to 1/15 by 1:1 focus.
Misinformed statement #2. When using the command dial, the camera is holding the effective aperture the same, so the exposure should and does remains the same.
3/ At infinity focus the 105mm aperture needs to be 37.5mm diameter to be f2.8.
There seems to be agreement the effective focal length of the 105 macro G is close to 74mm at 1:1 focus.
The aperture is still 37.5 mm diameter at 74mm focal length equivalent.
74mm divided by 37.5mm aperture size is remarkably close to effective aperture f2!
Misinformed statement #3. The
physical or nominal aperture could be as wide as f/2. It need not be, because other lens components could restrict it to f/2.8. Quoting Piper's 1901 "A First Book of the Lens:"
"It is important to remember that the effective aperture of the lens does not necessarily correspond with the actual aperture of the diaphragm, and, also, it is under certain conditions, to vary in diameter with variations in the distance of the object."
4/ By 1:1 focus either lens has changed from f2.8 at infinity to effective f2.
Misinformed statement #4. You clearly don't understand what effective aperture means, and apparently refuse to accept or change your ignorance.
If you do not then agree with me I have lead a horse to water but may not have persuaded it to drink.
That's because horses aren't stupid enough to drink the poison water you try to lead them to.
You ignore a leading source which I have provided - which being a 1977 publication seems not to be on the web.
An unverifiable source is not a source. I can't tell if you are misinterpreting it or not. So tell, me, where does this publication support your previous claim about depth of field, which you just contradicted above?
Scan an excerpt or come up with something we can verify. And while you're at it, where's that "conventional depth of field table" you keep going on about?
Kodak researched why then newly introduced internal focus lenses which "breathed a lot" gave a wrong exposure when applying a hand held meter reading and allowing for magnification, particularly when using extension tubes.
They published their research as to why in "Close-up Photography and Photomacrophotogry" in 1977.
The gear available in 1977 forced you to change physical aperture instead of effective aperture. If I were to put, say, my Tamron 180mm f/3.5 on a dumb extension tube today, the same would also be true. But with CPU lenses Nikon takes into account the change in focal length. Otherwise, since the 105mm VR is a telephoto lens, the effective aperture at 1:1 would be smaller than f/5.6.
In other words, your alleged "source" appears to be totally irrelevant to your claims. But feel free to buy me a copy if you want me to verify that -- there's one for sale for $12 on Amazon.
This book seems to be the first mention of the "P" factor (pupillary exit factor) which it is now "fashionable" to refer to as focus breathing as regard effective focal length.
Misinformed statements #5 and #6.
- Pupil Magnification (p) is independent of focus breathing. All telephoto lenses have a p value of less than one, whether they change focal length with focus distance or not. All symmetric lenses have a p value of one. They typically exhibit focus breathing by the cine definition but do not change focal length with focus distance despite your claims to the contrary. All retrofocus lenses have a p value of greater than one, whether they change focal length with focus distance or not. It is not "fashionable" to conflate the two out of ignorance as you just did.
- As far as I can tell, you're the only person to use the phrase "pupillary exit factor."
- Pupil Magnification (p) was mentioned by Thomas R. Dallmeyer in 1899. It's incorporation into the depth of field equations used today is typically credited to Hardy & Perrin's 1932 work, "The Principles of Optics"
Sources mentioned above:
https://archive.org/details/telephotographye00dallrich
https://archive.org/details/ThePrinciplesOfOptics
https://archive.org/details/gri_33125013853433
