OhOh, future of CL?

[Speeding]

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6 minutes ago, RM8 said:

Many thanks! I just assumed a "FF lens" throws a larger 43mm image circle on its focal plane from which the APS-C sensor takes the "sweet" central part

It does (you are correct).  But distortion in the center portion of a FF lens is also present on the APS lens.  Where you sometimes see an advantage for FF lens on APS body is that the crop factor favorably impacts vignetting.  

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2 minutes ago, aksclix said:

what I meant was the opening of a f/5.25 aperture is NOT  bigger than the 24 f/3.5 so it does not make sense to call a f/3.5 lens on a full frame as f/5.25 on APS-C when the actual image circle covers more than the crop sensor itself

The portion of the image circle visible on APS with 24 f/3.5  is identical to the portion of the image circle visible on a FF 36mm f/5.25 lens on FF body

[jaapv]

Exactly the same number of photons per mm. Mms are always the same. One of the basics of geometry….

[aksclix]

3 minutes ago, Speeding said:

The portion of the image circle visible on APS with 24 f/3.5  is identical to the portion of the image circle visible on a FF 36mm f/5.25 lens on FF body

And still it’s a f/5.25? 

[aksclix]

43 minutes ago, robgo2 said:

but mounting a bulky lens onto a compact camera 

This one doesn’t seem bulky does it? It’s a Minolta APO 200 f/2.8

 

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[Speeding]

1 minute ago, jaapv said:

Exactly the same number of photons per mm. Mms are always the same. One of the basics of geometry….

Can you explain how sensors 24mm x 16mm "are the same" as sensors 36mm x 24mm?  Photons are the same...mm are not.

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3 minutes ago, aksclix said:

And still it’s a f/5.25? 

Identical in AOV, DOF and light gathering to a 36mm f/5.25

[jaapv]

5 minutes ago, aksclix said:

And still it’s a f/5.25? 

Just let him overexpose…🤣

[RM8]

22 minutes ago, SrMi said:

What focal length was that? I assume wide.

Many FF lenses, especially wide-angle lenses, also rely on SDC (software distortion correction). Q2's lens is an example. With digital, the trend is to rely more on SDC than to make the lens heavier and more expensive by correcting distortions in the lens itself. I am not a purist in that context, as I care only about the output. I just wish we could tune the amount of SDC applied (I believe DxO PhotoLab can do that).

Of course on the Q2's fixed lens I imagine they've done SDC to their heart's content. In the CL software, is any SDC performed depending on the lens mounted? And if so, also for non-Leica lenses? As mine correctly recognized my Sigma 24mm. Just curious

[Speeding]

7 minutes ago, jaapv said:

Just let him overexpose…🤣

With ISO set to Auto...?  

[NZDavid]

36 minutes ago, jaapv said:

The concept of light gathering has been comprehensively debunked. The amount of light per square mm remains exactly the same As for shallow DOF, being predominantly a nature and landscape photographer I regard shallow DOF as an aberration. I am totally chuffed that my S5 offers excellent 6k focus stacking in-camera.  It saves a lot of computer time. As for shallow DOF emphasizing the subject, shouldn’t composition do that?  I hate fuzzy ears and nose portraits. 

Early photographers had no choice about "fuzzy ears and nose portraits" because these are what the lenses and the format of the time produced. And if you stopped down for greater DOF you'd require a super long exposure and the subject would move! I'm pretty sure these photographers would have loved a compact size and greater DOF.

My brother-in-law in Australia certainly does. He is getting a new Lumix G9 and already has a raft of lens, including Leica -- he finds the format is great for nature and wildlife.

[adan]

18 minutes ago, Speeding said:

Except the mm...they're not the same are they?  You can't debunk photons.  

Bottom line - the smaller lens is passing fewer photons, but they only have to cover a smaller area of silicon/film. So the net photons per square mm hitting the sensor is identical with an f/3.5 24mm on APSC and an f/3.5 36mm on FF.

Use a hand-held meter - make an exposure with both lenses on their appropriate sensors at f/3.5. Use same ISO and shutter speeds - the images will be equally bright. If the ASPC lens passed light as though it were "f/5.25" the APSC picture would be 'way underexposed.

It is equivalent to - you need 250 bandages of size X to cover an adult body. But you only need 40 of the same bandages to cover the smaller body of a child. Surface area is a critical variable in photography as well.

This is in fact the whole reason why we photographers use "f/stops" instead of simpler linear dimensions like "3mm opening" or "25mm opening" - the fraction of focal-length automatically accounts for how the brightnesses of the scene are laid down on the photo-sensitive surface area. "f/3.5" produces the same brightness per unit of film or silicon surface area (i.e. exposure), regardless of where it is a 90mm f/3.5 lens on 35mm film, or on 4x5 film, or on 6x6 film, or a 24mm lens on APSC, or on 35mm.

DoF - or at least the size of blur circles - is a different thing, where indeed an APS lens of "equivalent field of view" will produce smaller out-of-focus blurs than on FF (and even less than on 6x6, and vastly less than on 4x5 ).

[Speeding]

4 minutes ago, NZDavid said:

Early photographers had no choice about "fuzzy ears and nose portraits" because these are what the lenses and the format of the time produced. And if you stopped down for greater DOF you'd require a super long exposure and the subject would move! I'm pretty sure these photographers would have loved a compact size and greater DOF.

My brother-in-law in Australia certainly does. He is getting a new Lumix G9 and already has a raft of lens, including Leica -- he finds the format is great for nature and wildlife.

MFT is very fun format - he will enjoy.  

[lct]

13 minutes ago, RM8 said:

In the CL software, is any SDC performed depending on the lens mounted? And if so, also for non-Leica lenses? As mine correctly recognized my Sigma 24mm. Just curious

SDC depends only on the code of the lens, as far as the CL is concerned at least. If you code a non Leica lens as a Leica lens, SDC will be the same as for the later. 

[jaapv]

27 minutes ago, Speeding said:

Can you explain how sensors 24mm x 16mm "are the same" as sensors 36mm x 24mm?  Photons are the same...mm are not.

Given the same sensor architecture with the same pixel density you will see no difference other than magnification. If the MP count is the same the noise floor will be higher. 

[Speeding]

5 minutes ago, adan said:

Bottom line - the smaller lens is passing fewer photons, but they only have to cover a smaller area of silicon/film. So the net photons per square mm hitting the sensor is identical with an f/3.5 24mm on APSC and an f/3.5 36mm on FF.

Use a hand-held meter - make an exposure with both lenses on their appropriate sensors at f/3.5. Use same ISO and shutter speeds - the images will be equally bright. If the ASPC lens passed light as though it were "f/5.25" the APSC picture would be 'way underexposed.

It is equivalent to - you need 250 bandages of size X to cover an adult body. But you only need 40 of the same bandages to cover the smaller body of a child. Surface area is a critical variable in photography as well.

This is in fact the whole reason why we photographers use "f/stops" instead of simpler linear dimensions like "3mm opening" or "25mm opening" - the fraction of focal-length automatically accounts for how the brightnesses of the scene are laid down on the photo-sensitive surface area. "f/3.5" produces the same brightness per unit of film or silicon surface area (i.e. exposure), regardless of where it is a 90mm f/3.5 lens on 35mm film, or on 4x5 film, or on 6x6 film, or a 24mm lens on APSC, or on 35mm.

DoF - or at least the size of blur circles - is a different thing, where indeed an APS lens of "equivalent field of view" will produce smaller out-of-focus blurs than on FF (and even less than on 6x6, and vastly less than on 4x5 ).

In your example the DOF is not the same and neither is the shot noise.  When you place a 24/3.5 FF lens on APS provides the same exact AOV and DOF and light gathering as 36mm f/5.25 on FF.  The actual F-number always tells you the intensity of the light on each square mm of the sensor - this doesn't change with sensor size.  The equivalent aperture takes into account how many square mm of sensor you've put behind the lens.

[Speeding]

4 minutes ago, jaapv said:

Given the same sensor architecture with the same pixel density you will see no difference other than magnification. If the MP count is the same the noise floor will be higher. 

You will see a difference in both DOF and noise.  Mounting a FF 24mm/3.5 lens on the CL provides the same exact AOV and DOF and light gathering as 36mm f/5.25 on FF.  

[adan]

29 minutes ago, Speeding said:

The actual F-number always tells you the intensity of the light on each square mm of the sensor - this doesn't change with sensor size. 

Yep!

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[SrMi]

46 minutes ago, RM8 said:

Of course on the Q2's fixed lens I imagine they've done SDC to their heart's content. In the CL software, is any SDC performed depending on the lens mounted? And if so, also for non-Leica lenses? As mine correctly recognized my Sigma 24mm. Just curious

You probably know this. SDC is always performed in post-processing software. The camera only writes instructions (EXIF) in the raw files. In case of Sigma 18-50, the camera embeds WarpRectilinear data.

[SrMi]

37 minutes ago, jaapv said:

Given the same sensor architecture with the same pixel density you will see no difference other than magnification. If the MP count is the same the noise floor will be higher. 

At the same output level, larger sensors will have less noise. At same sensor size and same output level, the noise characteristic is approximately the same regardless of MP count.