[Dartmoor Dave]

The whole fallacy of this thread, I think , is that the proponents kept insisting that signal to noise was related to sensor size, by the incorrect interpretation that signal to noise in each well is somehow related to integrated light on the overall sensor , so a larger sensor is somehow better. That is false in my opinion.

It also seems that they either don't know, or are choosing to ignore, the fact that the sensor is an analog device. Noise can occur anywhere in the analog stages downstream from the sensor, up to and including the A/D converter.

[lytrytyr]

The whole equivalence thing is useless.

Sorry, but after just learning a new lens (08 wide zoom)
on a new format (1/1.7") on a new Q7,
I couldn't disagree more.

Anyway, people don't need to know 35mm to use equivalence.
There just needs to be one standard,
and as a format in the middle between P&S and view cameras,
35mm works very well for that purpose.

[marcusBMG]

What did i do??? I'm off to hide in a cave for a week.!

[normhead]

Some philosophies are designed to reveal the truth, some are there to simplify reality so much that simple folk can make a go of it, even if they don't understand it.

[marcusBMG]

No, no, no, Markus, you've let the idiots drag you down to their level. The simple answer is the right one. There is no "compensation" in camera regarding ISO values. And there doesn't need to be. They are arguing about "exposure," which is NOT the same thing as total light gathered. The total light gathered is simply varying with the size of the sensor, that's it. It takes nothing more to explain it.

---------- Post added 10-10-2014 at 09:42 PM ----------



Still arguing exposure, NOT the same thing as total light gathered.

Yes i appreciate this now sorry.
I have added an update to the post quoted (#22).

[wombat2go]

t also seems that they either don't know, or are choosing to ignore,

Well at least one member who was on the side of the title was thrown off track by incorrect information read on another forum.

The internet is a huge benefit to all, but a downside is that we have to be careful to verify the information before relying on it.
I rarely follow the "high tech magazine pseudo science" or fan club threads about lenses etc but the title immediately seemed problematic and motivated me to follow through this one.

And I commend everyone on the thread who remain calm and friendly and even provide some much needed humor while it gets thrashed out. We can all learn from it

[jsherman999]

But you have seen firsthand how people that crop within a format still like to say if they crop their 300 2.8 to the fov as a 600m that it will produce an image that looks like a 600 F2.8
and now that we have such high MP counts that we can use a lot of cropping equivalence is also a important part even when you are only using 1 format

Very true.

[kh1234567890]

It also seems that they either don't know, or are choosing to ignore, the fact that the sensor is an analog device. Noise can occur anywhere in the analog stages downstream from the sensor, up to and including the A/D converter.

Also larger CMOS sensor elements have larger capacitance so the increase in the measured voltage that each incident photon causes will be less in proportion.

[jsherman999]

Thank you for providing references that I requested

You're welcome!

In Post #1 of your reference was this summary:
Quote:
"This kind of rough calculation helpfully leads quickly to seeing that the micro four thirds camera normal lens, is going to have to be 25mm F/1.0 lens, to "gather the same amount of light" as a full-frame optic. Thus u43 lenses need to be "a lot faster" than their full frame counterparts to get you the same low-light capability."

I can respond, without tech and maths etc , as I am sure any photographer can, by advising that I have adaptors for my Pentax K lenses, typically 1:2.8 28mm etc, so I use them on my Olympus M4/3, my Pentax Ist-ds , my Pentax K-01, and my Pentax MX.
The experience is as it has been documented for 100 years and in dslrs too, that it is independent of format; the u43 lenses work by f/- and shutter the same as on any format, that is , for example "sunny 16" etc.

So in my opinion, the Post#1 in your reference is incorrect.

(I think you mean post #2? anyway...). When you say "work by f/- and shutter the same as on an any format" what you're talking about is exposure - which isn't in question here. In terms of exposure, f/2.8 = f/2.8 = f/2.8, and it will give you the same light density and the same shutter speed on any format, P&S up to the Hubble. (When that poster said "gather the same amount of light" they were not talking about exposure.)

But with images of the same FOV and exposure on different formats, your f/2.8 gives you a different physical aperture (lens pupil diameter,) which alters the total light being captured by the sensor. Light density doesn't change, and it doesn't have to for the total light to be different.

Please see the Falk Lumo link I provided for another excellent overview on this. (link)

You referred me to read a post from "The_Suede" from your referenced link, the summary at the end of that post was this:
Quote:
"Light gathering ability = (crop ratio) / (f-stop)
In the end that means that to collect as many photons per second from a certain scene, you need to change f/# with the same factor as you change the crop ratio."

...

I can respond that I disagree, and
again I am sure that any reasonable photographer would disagree with that conclusion. There is a plethora of references that would provide the correct way to set f/- on any format size of dslr, and it is demonstrated that it does not change by format size.

Here again I think you're responding to what you this is an assertion on exposure, not total light. Let's break down what he said further, maybe you can talk about specifically what you disagree with (and beyond this, I encourage you to take it up with him on dpreview, he's a nice fellow in general who will respond to questions )

He summarized, at the end of that post:

The two basic parts are really:

f/# determines image plane exposure
exposure is "amount of light energy per area unit"

So there's exposure, which I know from what you wrote you agree with. Next:

-So you get the light energy amount that your system "gathered" by:

(scene average luminance) / (f-stop)^2 * (sensor area) * (exposure time)

The preceding is what he derived the formula you had issue with, so is that ^^ wrong in your view?

I'll include the rest below so we don't necessarily have to go back to the thread for reference on this point:

And from that you can get that the system "light gathering ability" when keeping scene average luminance and exposure time constant is:

Light gathering ability = (sensor area) / (f-stop)^2

Since (sensor area) is the square function of crop ratio this can be further simplified by doing a square root on both, and then you get:

Light gathering ability = (crop ratio) / (f-stop)

In the end that means that to collect as many photons per second from a certain scene, you need to change f/# with the same factor as you change the crop ratio.

And again that last sentence is not referring to exposure, it refers to (basically) needing to open up a lens more, match the physical aperture for that FOV, on a smaller sensor to gather as much total light.

[ElJamoquio]

Equivalence is dumb. It uses math.

[Kunzite]

You probably mean: "Equivalence is dumb. It uses math in a dumb way."

[jsherman999]

Also larger CMOS sensor elements have larger capacitance so the increase in the measured voltage that each incident photon causes will be less in proportion.

This is fully true, but there's going to be a trade off point where the larger capacitance isn't gaining enough to make the lack of resolution worth it. In other words, a 1-pixel FF sensor is going to have radically great per-pixel performance... but will only have 1 pixel. Right now that trade-off point with current sensor tech seems to be at around 5 microns. Then also there are mitigating effects.

---------- Post added 10-11-14 at 09:51 AM ----------

What did i do??? I'm off to hide in a cave for a week.!

You didn't start the fire. It was always burning, since the world was turning. (name that band)

[Rondec]

Equivalence is dumb. It uses math.

The biggest problem with equivalence to me is that it ends up confusing concepts that are actually quite simple. People end up getting part of the concept (the field of view thing) and not other parts (aperture, iso). And in the end, it is very un-useful when it comes to creating images. Because I don't go out shooting thinking about equivalence. I think about field of view on the camera I am shooting and the depth of field I need to shoot to get the image I want. I don't need to convert my DA 15 or FA 31 into full frame terms in order to figure that out -- that would actually make things harder for me, because I am not well versed in full frame cameras and how particular focal lengths behave on them.

I don't think it is a problem if it makes it easier for some people to understand how formats relate to each other, it just has been my experience that it actually makes it more confusing for most people.

[normhead]

You probably mean: "Equivalence is dumb. It uses math in a dumb way."

I would use, "imprecise" rather than dumb. Although it could be argued that taking something that is precise and turning it into something imprecise is dumb. Through changing technologies Aperture and ISO have remained constant. These other concepts people are trying to involve are good concept to be aware of, that's not the issue.

For example, saying a 2.8 lens on a small sensor is actually 9.3 in terms of DoF is confusing... because 2.8 s part of the equation used for exposure, and DoF is not.
Calculating DoF in stops is confusing because two concepts with different meanings are using the same terminology. And that's dumb as well.

[Kunzite]

Me too, but in that instance I used what I had
Anyway, that was another "equivalence" mantra, "it must be right because it's using math!" (somehow I keep reading that as "meth" ) As if math can only be used in a right and relevant way.