[Brightcolours]

Film speed and sensor speed are not the same - but there's a standard for them: https://en.wikipedia.org/wiki/Film_speed see  The ISO 12232:2006 standard and Measurements and calculations.

 

Btw., sensor area doesn't play a role in the formulas, if I'm not mistaken.

 

Now, instead of talking theoretically I wanted to see if I'm wrong. I set up the same ISO, measuring method and aperture. First was  23/1.4 (APS-C) and 35/1.4 (FF)

 



 

Both 1/200 as shutter speed - where is the equivalence? Should be 1/200 × 1.5 = 1/133

 

Next with f/8: â…›" on both cameras

 



 

Next were 35/2 (APS-C) and 50/1.4 (FF), I don't have a 52.5 mm lens

 



 

1/40 for APS-C × 1.5 = 1/26⅓ for FF - but FF shows 1/50. Equivalence?

 

You can remain in your thinking model and I will in mine. I just never saw a proof for your reasoning. Maybe with a better lit test scene than mine.

So we agree that the old film idea about speed is not valid, as we do not have sensors of same sensitivity very often, and we can set ISO settings to whatever we want. So. "speed" with digital is not what it used to be.

 

Equivalence:

You took care of setting an equivalent focal length. You took care of setting an equivalent f-stop. You forgot to set an equivalent ISO setting. Why?

[wim]

So we agree that the old film idea about speed is not valid, as we do not have sensors of same sensitivity very often, and we can set ISO settings to whatever we want. So. "speed" with digital is not what it used to be.

 

Equivalence:

You took care of setting an equivalent focal length. You took care of setting an equivalent f-stop. You forgot to set an equivalent ISO setting. Why?

 

Equivalent iso setting is not valid, from a "sensitivity" or light ratio POV.

Iso equivalence is only related to sensor noise, nothing else. With a 4x smaller sensor you need a 4 times (2 stops) lower iso to have the same noise at the same size image, compared to FF, that's all.

 

The way isos and light are related is in amount of light per square standard area size (f.e., per square mm). This is why you get exactly the same exposure parameters (aperture and shutter speed) for the same iso with any format camera, wether it is 4/3, APS-C, FF, MF, large format. or anything else for that matter.

 

There is indeed less total light captured, but that is purely because of the sensor or medium size. Amount of light per square mm, which is what iso and metering is based on, is still the same.

 

However, a 4/3 sensor is 1/4 of the area of a FF sensor, and hence if one makes an enlargement to exactly the same size as, e.g., an image from a FF sensor, say a 20x30, the FF image print will have 4x less noise, as it has been enlarged 2x less linearly (4x area) provided of course the sensors are of comparable quality.

 

This is where "iso equivalence" originates from - not real iso equivalence, but equivalence with regard to noise.

 

It should also be noted that equivalence should always be specifically referred to, as an F/1.4 4/3 lens is still an F/1.4 lens, whether it creates an 4/3 image circle or not. Due to the smaller image circle and shorter absolute focal length, it just has more DoF.

 

BTW, it is entirely possible to get similar narrow DoF on micro 4/3 as on FF, more or less anyway: just use a Metabones Speed Booster Ultra 0.64x, with FF lenses. Works like a charm. My 85 F/1.2 becomes a 54.4 F/0.8 lens, or a 108.8 F/1.6 in equivalent terms. This is narrow enough to struggle to get a single eye in focus in a tight portrait setting. And sharpness is incredible, as resolution increases with the compression of focal length.

 

In short, I now have the benefits of both worlds, FF with all the stuff I like to do, but with heavy equipment, micro 4/3 with light equipment with increased DoF, or micro 4/3 with a similar playing ground as with FF when i need that, just that the equipment becomes quite heavy again (but that is ok when you really need it).

 

Kind regards, Wim

[JJ_SO]

I'm very glad about your post, Wim. That's exactly what I was talking about and a couple of things more.

 

BC, I don't know why you say "You took care of setting an equivalent f-stop"- that's not what one can see in my pictures, in each picture you see the same f-stop on both lenses. That's what I wanted to point out: Same ISO, same F-stop, equal lighting = same shutter speed.

 

What I want to add: ISO was also in film days only "an idea", depending on what one wants as final result. At least in black and white - and what else are sensors than 3 monochromatic films with different color sensitivity, be it Bayer, X-Trans or Foveon pattern? ISO is not a value like 20 °C or 2,234 mm. In film days the setting of the exposure meter very much depended on planned contrast - I guess you know about zone-system? Not a single b/w film was usable with the nominal ISO, DIN or ASA number, all of them needed more light to remain defined enough in the shadows.

[Brightcolours]

Equivalent iso setting is not valid, from a "sensitivity" or light ratio POV.

That, of course, is incorrect.

It is very valid for light.

An equivalent focal length, gives the same field of view.
An equivalent f-stop setting, gives the same depth of field.
An equivalent ISO setting, gives the same amount of light.

Iso equivalence is only related to sensor noise, nothing else.

The "only" part is nonsense...
The whole single reason it is "related to sensor noise" is because equivalent ISO settings will form the image with the same amount of light.

With a 4x smaller sensor you need a 4 times (2 stops) lower iso to have the same noise at the same size image, compared to FF, that's all.

 
The way isos and light are related is in amount of light per square standard area size (f.e., per square mm).

Because you used the same amount of light.

Light per square area size is.... totally not interesting in any way. The paradigm has shifted going from film to digital. With film, when using the same film, it made some sense. When using two totally different films, not so much.

This is why you get exactly the same exposure parameters (aperture and shutter speed) for the same iso with any format camera, wether it is 4/3, APS-C, FF, MF, large format. or anything else for that matter.
 
There is indeed less total light captured, but that is purely because of the sensor or medium size. Amount of light per square mm, which is what iso and metering is based on, is still the same.

ISO is not based on amount of light per square mm. You made that up... Or just misunderstood things that way.
https://en.wikipedia.org/wiki/Film_speed#Digital

However, a 4/3 sensor is 1/4 of the area of a FF sensor, and hence if one makes an enlargement to exactly the same size as, e.g., an image from a FF sensor, say a 20x30, the FF image print will have 4x less noise, as it has been enlarged 2x less linearly (4x area) provided of course the sensors are of comparable quality.
 
This is where "iso equivalence" originates from - not real iso equivalence, but equivalence with regard to noise.
 
It should also be noted that equivalence should always be specifically referred to, as an F/1.4 4/3 lens is still an F/1.4 lens, whether it creates an 4/3 image circle or not. Due to the smaller image circle and shorter absolute focal length, it just has more DoF.
 
BTW, it is entirely possible to get similar narrow DoF on micro 4/3 as on FF, more or less anyway: just use a Metabones Speed Booster Ultra 0.64x, with FF lenses. Works like a charm. My 85 F/1.2 becomes a 54.4 F/0.8 lens, or a 108.8 F/1.6 in equivalent terms. This is narrow enough to struggle to get a single eye in focus in a tight portrait setting. And sharpness is incredible, as resolution increases with the compression of focal length.
 
In short, I now have the benefits of both worlds, FF with all the stuff I like to do, but with heavy equipment, micro 4/3 with light equipment with increased DoF, or micro 4/3 with a similar playing ground as with FF when i need that, just that the equipment becomes quite heavy again (but that is ok when you really need it).
 
Kind regards, Wim

[Brightcolours]

I'm very glad about your post, Wim. That's exactly what I was talking about and a couple of things more.

 

BC, I don't know why you say "You took care of setting an equivalent f-stop"- that's not what one can see in my pictures, in each picture you see the same f-stop on both lenses. That's what I wanted to point out: Same ISO, same F-stop, equal lighting = same shutter speed.

My bad. Thought you were showing a more sensible comparison. Here, only the FOV is being used.

 

What I have been pointing out is

Same FOV, same DOF, same lighting = same shutter speed.

 

That is where everything is similar or same, just by using equivalent settings. What is your issue with that, exactly?

[Brightcolours]

Meanwhile, the lens has officially been launched.

15 elements in 12 groups, of which 2 aspherical elements. Length and width:70mm. Weight: 335 grams. 62mm filter size.

 

Bigger and heavier than the equivalent we were discussing (Canon EF 24mm f2.8 IS USM on FF 135 format, which weights 280 grams (11 elements in 9 groups), is 55.7mm x 68.4mm in size, and has a filter size of 58mm).

 

The Leica badged lens has a metal barrel, and is described to be dust and splash proof. Appears to be a nice lens.

[JJ_SO]

BC, keep your opinion, I keep mine.

[Brightcolours]

BC, keep your opinion, I keep mine.

Don't confuse opinion with facts. I write about the facts, you may keep your opinion of course.  :lol:

It will not be a bad thing to learn about what I explained, though.

[JJ_SO]

Except it's wrong and you confuse facts with phantasy.

 

You're even to lazy to show evidence. Blurbing theoretically in a complete wrong direction doesn't convince me. You stick extremely stubborn to "same FOV, same DOF" - NO! All I say is, f/1.4 in terms of correlation to shutter speed and ISO is not depending on sensor or film size. Never was, never will be.

[Brightcolours]

Except it's wrong and you confuse facts with phantasy.

Uhmm, no. Here you are confusing your fantasy with my facts again. Yes, fantasy is written with an F. 

You're even to lazy to show evidence.

Evidence of what? I already gave you the calculations (= evidence B) ) to show you that indeed, 12mm f1.4 on MFT is equivalent (as equivalent as things can be with different aspect ratios) to 24mm f2.8 on full frame 135 format. What more "evidence" do you require?

Blurbing theoretically in a complete wrong direction doesn't convince me. You stick extremely stubborn to "same FOV, same DOF" - NO! All I say is, f/1.4 in terms of correlation to shutter speed and ISO is not depending on sensor or film size. Never was, never will be.

And you have the odd idea that it is in any sense valuable to use the same ISO number setting on different cameras. No idea why you think that is in any way meaningful.

Nor is it meaningful to use the same f-value, as the f-value stands for apparent aperture size. Which means that you oddly enough place importance of setting one camera a f/1.4 where f = 12mm and the other camera at f/1.4 where f = 24mm. So you find it meaningful/logical to set one camera at 12 / 1.4 = 8.5mm aperture, and the other at 24 / 1.4 = 17mm aperture.


Yeah, that makes so much sense. Well actually, it does not, and never has.


So, not only does the f1.4 not mean the same on the different lenses, and does for instance "ISO 100" not have an actual significant meaning or importance, you end up with very different images due to the different DOF. How interesting to keep on repeating that useless "comparison".

 

Why not compare 50mm f1.4 on MFT to 50mm f1.4 on FF? You will find that with the same ISO number setting you will get the same exposure time when using a similar exposure metering method. 

 

Or how about putting a 500mm f8 lens on a Nikon D700 at ISO 3200 and a 20mm f1.4 lens on a Nikon D5 at ISO 100. Again, similar exposure times. Now you not only have different DOF, but also different FOV!

 

It is not that hard to come up with pretty senseless comparisons  :lol: