[Guest]

Lens size is hard to judge; after all there are large fuji and 4/3 lenses (not so many micro 4/3) and tiny zuiko full frame lenses as well as leica M lenses.

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I have one request and we leave all inflamatory equivalence commetns to this thread and ban anyone who charges into another thread with those same old comments from those threads rather than closing the threads ?

[Brightcolours]

It is always ok to explain lens equivalence. What in my opinion is the crap going on is people denying the simple concept, and then blame me in particular for "inflammatory" comments. It is called trolling.

 

I never understand why some take lens equivalence to mean one system is superior in everything than another.... Understanding which equipment is suited to what in particular is an asset to any photographer's knowledge. 

[Klaus]

Banning per thread isn't possible

[JJ_SO]

If anybody would have an interest in absolute diameters of aperture diaphragm, we simply would not have those f-numbers. but just some diameters on each lens - which makes no sense at all.

 

If I have a waterhose of 2 cm inner Ø, I can fill a bucket of 10 liters in 1 minute, but a swimming pool of 1000 liters in - right - 100 minutes - okay, we don't fill an exposure as a volume but as an area, but the principle remains. The basic idea of f-numbers were not "feed a DoF calculator"  or "compare different sensors or negative sizes", but "use the exposuremeter to get a proper exposed result". These DoF calculators are nothing than mumbo jumbo which will never ever lead to "really sharp results over a certain distance from point A to B" but to "less blurred information within a certain distance difference, approximately". Number games, that are.

 

Using mathematical formulas and operating with estimated values is nothing else than bluffing, especially because the values of the airy discs to define "enough sharpness" are not constant over the whole field of view - center, border, corners - due to optical flaws of the lens itself. While closing down aperture, after f/8 diffraction leads to less sharpness. Effectively the whole maximum sharpness of the lens gets reduced, that's the price of huge DoF. While max sharpness is possible with a focus stack, a DoF calculator gives results of 3 digits behind the comma - nonsensical and not even taking focus drift in calculation.

 

Also, why using a DoF calculator if even lenses of the same values in terms of FL and aperture are not equal in front of a given sensor when it comes to bokeh? What good is a wide open lens if it creates a nervous bokeh?

 

I never saw equivalence-comparisons between mountainbikes and racing- or BMX-bikes, between lorries and race-cars, between castles and appartments. It appears to be only a phenomenon in photography, leads to nothing and is not important or helpful. Who wants to do the same with different systems? It's always the right system to be used for a certain task an for that only equivalence leads to wrong conclusions. 

[thxbb12]

Thanks Klaus for this great article (long overdue!).

It's well written even if some equivalent lenses don't fully compare. Globally, the comparison remains valid.

One thing that might be interesting would be to show some equivalent lenses purely from a focal point of view, not taking equiv. DOF in account. For instance, the Oly 9-18 f4-5.6 and the Pany 12-32 f3.5-5.6 are incredibly minuscule compared to (focal) equivalent lenses in larger sensors systems. Although the equiv. DOF is not comparable, in this specific case it's not of much relevance while the size benefit is huge. This applies to many lenses though.

[Austrian]

So I'm torturing you ONCE more ;-)

 

http://www.opticallimits.com/Reviews/986-equivalence

Thank you Klaus for the excellent article.

 

Clear and detailed enough for any practical use.

 

My comment and question is, what you and the community think about "equivalence of DOF" when the final target is to get the maximum depth of field? e.g. for landscape?

 

How do the different systems compare here? What about sensor size and diffraction?

 

Any thoughts with practical relevance :-)

 

Thank you and kind regards

 

Andreas

[Brightcolours]

Thank you Klaus for the excellent article.

 

Clear and detailed enough for any practical use.

 

My comment and question is, what you and the community think about "equivalence of DOF" when the final target is to get the maximum depth of field? e.g. for landscape?

 

How do the different systems compare here? What about sensor size and diffraction?

 

Any thoughts with practical relevance :-)

 

Thank you and kind regards

 

Andreas

Lets disregard diffraction softening on pixel level, because it is not part of equivalence.

Diffraction happens inside the lens, light "bends" around the edges of the aperture (simplistic way to tell it). 

 

Light ends up on a different place than it without diffraction would, which causes the softening.

 

Lets get an example.

 

MFT, 50mm f4 lens. 

FF, equivalent lens : 100mm f8. 

 

Both lenses will give a similar DOF. Both lenses have a similar aperture size:

50mm / 4 = 12.5mm, 100mm / 8 = 12.5mm.

 

The apertures are the same, so light gets diffracted around their edges in a similar fashion.

However, the aperture of the 100mm lens probably sits quite a bit further away from the film/sensor, which will mean that the impact of the diffraction on projected image of the f4 lens is less than that of the f8 lens ( extra the distance makes the diffracted light affect a larger area).

So, the MFT lens has less diffraction.

 

The MFT image capture device (sensor) is smaller, though. To get the same size image, we enlarge the image more than we do with the FF image.  The MFT diffraction softening impact gets magnified. 

 

The end effect: For both images, taken with equivalent settings, the diffraction softening impact is similar.

[obican]

Also if the pixel count is the same, smaller sensor will suffer more from diffraction.

 

It's really taking a few steps forward and few staps back all the time. It's not really like film anymore, with a well designed system, sensor size really does not matter*.

 

 

*I'm really not sure about the dynamic range and color though. My logic tells me they should also be two-steps-forward-two-steps-back but maybe they really benefit from having larger photosites. Any ideas?

[Brightcolours]

Also if the pixel count is the same, smaller sensor will suffer more from diffraction.

 

It's really taking a few steps forward and few staps back all the time. It's not really like film anymore, with a well designed system, sensor size really does not matter*.

 

 

*I'm really not sure about the dynamic range and color though. My logic tells me they should also be two-steps-forward-two-steps-back but maybe they really benefit from having larger photosites. Any ideas?

The image won't suffer more diffraction with higher pixel count. Higher pixel count will just show more detailed what is going on.

[Guest]

If all micro 4/3 lenses have equiv in full frame; why not just design a full frame system with the 'equiv' lenses and end up with the same system of the same size but the larger sensor ? If you can't then are they truely equiv ?