I just learned about f-stop equivalency...

[Ysarex]

Gentlemen, ladies, you are muddling my brain. Allow me to present what I have held to be true this far. Acceptable CoC is what you need on your sensor or negative in order to stay within the 0.2 mm limit in an 8x10 inch print. The table above makes perfect sense. Smaller neg calls for more lp/mm because of the bigger enlargement factor.

Yep, smaller neg = smaller CoC and larger neg = larger CoC and the same is true for sensors.

The sensor will only come into play, as will film grain, when it is not suitable to record the necessary lp/mm.

Nope. That's a huge leap from size of film and/or sensor to film grain. Nowhere in the explanation above is CoC linked to film grain and I'm betting the same goes for your old Rollei manual. The resolution of the recording medium can become a complicating factor but it is not used in DOF calculations as likewise the resolution of the optic is not used.

Look above at that calculation for hyperfocal distance and consider the variables used in the equation. I don't see a variable there for film grain and/or sensor resolution.

Other than that, it's a matter of optics. This may be a simplification, but it was good enough for the manual of my 1957 Rolleiflex, and I think it will have to be for me.

Joe

 

[bert0324]

Hi, I would quote if I knew how.
On "Nope" etc.: You may change that to "Yup". What follows is exactly what I, well, meant to say. Which still leaves me muddled on DOF. Is there any difference in DOF using 35mm film with a 75mm lens and 6x6 using the same focal distance? Forgive me if the math is not crystal to me (sustained brain damage, so at least I have an excuse

 

[Braineack]

I guess what it all comes down to is that the angle of my dangle is inversely proportional to the heat of my meat. Right?

 

[Ysarex]

Hi, I would quote if I knew how.
On "Nope" etc.: You may change that to "Yup".

Nope.

What follows is exactly what I, well, meant to say. Which still leaves me muddled on DOF. Is there any difference in DOF using 35mm film with a 75mm lens and 6x6 using the same focal distance?

To be very clear you mean to ask: is there any difference in DOF using 35mm film versus 6x6 film with a 75mm lens on each camera focused on a subject the same distance from both cameras and with the lens set at the same f/stop?

The answer is yes. It is also worth noting that you will not be taking the same photo in the above scenario. The photo taken with the 35mm camera recording much less information due to reduced angle of view.

Joe

Forgive me if the math is not crystal to me (sustained brain damage, so at least I have an excuse

 

[bert0324]

Yes, same f stop, let's not muddy the waters any more than we have to.
So two camera's, one 35mm, one medium format, both same focal length lens, same diaphragm.

"The answer is yes."

I'm sorry, but how can that be? If I crop a 6x6 (cm) in the darkroom to 24x36 (mm) I should have the same result as using a 35mm camera in the first place, shouldn't I? Angle of view as well as DOF? What am I missing here?

 

[Ysarex]

Yes, same f stop, let's not muddy the waters any more than we have to.
So two camera's, one 35mm, one medium format, both same focal length lens, same diaphragm.

"The answer is yes."

I'm sorry, but how can that be? If I crop a 6x6 (cm) in the darkroom to 24x36 (mm) I should have the same result as using a 35mm camera in the first place, shouldn't I? Angle of view as well as DOF? What am I missing here?

You're missing your crop in the darkroom. Having done that you're then comparing the DOF you get from 35mm film with the DOF you get from 35mm film ----- duuuuuh.

I've encountered the same misguided argument from folks trying to claim digital sensor size is not a DOF determinant. As a rule you get more DOF from APS sensor versus full frame sensor cameras. Someone then comes along and asks, but if you put the same lens on both and use the same f/stop and focus distance and then crop the FF down to the APS sensor size isn't the DOF the same? Well the DOF is the same when you compare an APS camera with an APS camera -- duuuuh. To compare APS with FF you have to use the FF. If you crop the FF then it's not FF. If you crop your 6x6 then it's not 6x6.

Joe

 

[bert0324]

Fair enough, but to me your argument boils down to it being dependent on the sensor/film format because - for the same angle of view - the lens will have to be of a different focal length. So in my thinking the latter is the defining factor.

 

[Derrel]

I think the best thing to have come out of the whole "equivalency movement" was that the manufacturers of lenses took notice, as the new religion-like fervor swept the enthusiast and serious prosumer lens categories. The rise of the bokeh craze, and the shallow depth of field craze, and the selective focus craze (all sort of interrelated) spawned a whole new generation of lenses with ever-wider maximum apertures, aimed at buyers who wanted to achieve "equivalency".

Cameraquestdotcom's website has some good examples of lenses that Cosina designed and then built, like lenses designed for the m4/3 format or micro four-thirds size sensor cameras,like like the super-fast f/.95 series of primes, made up of the Voigtlander 10mm f/.95, the Voigtlander 17mm f/.95, the Voigtlander 25mm f/.95, and the Voigtlander 42.5mm f/.95 lenses.

In effect, with the 2x Field of View factor of m4/3 compared to 35mm or FF or FX (24x36mm image capture size), because the image area is SMALLER, that format of camera makes getting deeper depth of field fairly easy; the equivalency movement people though, often express their desire for shallow DOF that can get them that "full-frame" degree of blurring; in order to get that, it became necessary to offer lenses that were significantly wider in aperture than the old-time lenses that had developed from say 1953 to 2010, so Cosina built these new, super-speed lenses.

Based on the old-fashioned 24x36mm film size, with an m4/3 sensor camera, the 10mm is like a 20mm, the 17 is a 35mm roughly, the 25mm is the 50mm equivalent, the 42.5mm is the 85mm equivalent--and ALL OF THOSE primes have blazing f/.95 max apertures.

Cosina lenses are made in Japan, and have very lovely, high-quality build, feel,and operation, but even the no-name Chinese factories have come out with some super-speed lenses at lowish prices, all based on the desire to achieve "equivalency". These newer, super-speed lenses bring a LOT of light-gathering power to small-sensor cameras, they bring the option for shallow DOF effects, and most are fairly high-grade optics that perform well.

 

[table1349]

Three bags of pop corn, that will be $35.00. Please enjoy the movie.


Now this is a circle of confusion.

Unless you live in the UK, Australia, and a few other countries that got the original plans for the steering wheel backwards in their design.

 

[Ysarex]

Fair enough, but to me your argument boils down to it being dependent on the sensor/film format because - for the same angle of view - the lens will have to be of a different focal length. So in my thinking the latter is the defining factor.

I'm not making "my argument." I have explained how DOF is calculated and understood by the photographic industry (I do agree with the industry standards). Why does your thinking require only one to be the defining factor? They are both defining factors.

Joe

 

[bert0324]

@ Joe: My thinking does not "require" there to be one defining factor, but in spite of your much appreciated efforts that is simply the way I understand it. My limitation, I'm sure. I propose we let it rest here.

 

[Braineack]

Fair enough, but to me your argument boils down to it being dependent on the sensor/film format because - for the same angle of view - the lens will have to be of a different focal length. So in my thinking the latter is the defining factor.

what does the AOV have to do with anything?

same spot, same lens, same subject.