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InFlight
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PostMon Apr 27, 2020 9:48 pm 
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Above 1/60th your relying on Image Stabilization.  I understand what it can do and how it works.  That fact that you want to use up to 4 stops of stabilization to shoot slow shutter speeds hand-held is a choice.

Compared to Full Frame, to achieve the same image m4/3

Focal Length needs to be halved
Aperture needs to be doubled

For a FF 24mm ISO 100 1/250, and m4/3 12mm ISO100,1/250
For m4/3 you need multiple the Aperture by the crop factor to get matching light levels.  Thus a Full Frame f/16 would be need f/8 for the same exposure. Otherwise +3 stops of shutter speed.

The shorter the lens focal length, the longer the DOF.  Because of the high crop factor, m4/3 need 1/2 the focal length.  However focal divider is completely offset by the Aperture size doubling.  So there is no net improvement in DOF.

The bokeh issue is ultra fast (2x Aperture) lens needed.

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gb
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PostTue Apr 28, 2020 7:05 am 
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InFlight wrote:
Above 1/60th your relying on Image Stabilization.  I understand what it can do and how it works.  That fact that you want to use up to 4 stops of stabilization to shoot slow shutter speeds hand-held is a choice.

One that allows not using a tripod in most all cases. I can just handhold in lower light conditions providing there is no subject motion without raising the ISO. I generally shoot base ISO, but will raise ISO to 1600 in rain forests on cloudy days and also variously raise ISO when shooting birds.

Quote:
Compared to Full Frame, to achieve the same image m4/3

Focal Length needs to be halved
Aperture needs to be doubled

For a FF 24mm ISO 100, and m4/3 12mm ISO100
For m4/3 you need multiple the Aperture by the crop factor to get matching light levels.  Thus a Full Frame f/16 would be  need f/8 for the same exposure.

This is a misconception. Just because a FF camera has a bigger sensor and captures more total light, does not mean it captures more light per unit area of the sensor. If you and I stood side by side and shot the same scene with the same aperture we would get the same scene exposure +- variances in software exposure preferences of the two systems. DOF, though, would not be the same.

Quote:
The shorter the lens focal length, the longer the DOF.  The because of the high crop factor, m4/3 need 1/2 the focal length.  However focal divider is completely offset by the Aperture size doubling.  So there is no net improvement in DOF.

There is - for the same aperture on two different systems with different sensor sizes. FF can compensate if the goal is greater DOF by narrowing the aperture by a factor of 2. But doing so, will underexpose the image, accordingly. Hence in FF you would also have to raise the ISO by the same factor of two.

Again you can read all about this if you look at the "Depth of Field Calculator" at Cambridge in Color. https://www.cambridgeincolour.com/tutorials/dof-calculator.htm

Quote:
The bokeh issue is ultra fast (2x Aperture) lens needed.

The other factor, of course, that enters in to the choice of aperture is diffraction. Each different lens has a different curve for diffraction/aperture and also a design bias for center versus edge and corner sharpness (at different FL's for zooms). These curves vary by manufacturer and lens. So, it is a good idea to know for your lens what that looks like. Because of the greater DOF at a particular aperture, m4/3 lenses, for instance, are generally sharpest around F4 to F5.6. But the fall-off in diffraction does not become significant until after F8 for shorter FL lenses. By F11 I have generally lost around 12-15%; so I avoid that when I can. I found F16 with my lenses to be too poor and would only use that for handheld macro when I can't focus stack using a tripod. I have only a few such shots. I really doubt I can see a loss of resolution at 8%, but believe I can readily see that at 15%.

Clearly, FF cameras have a different diffraction curve. You can look these up for particular lenses at Optical Limits and Lenstips.
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InFlight
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PostTue Apr 28, 2020 2:04 pm 
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gb wrote:
This is a misconception. Just because a FF camera has a bigger sensor and captures more total light, does not mean it captures more light per unit area of the sensor. If you and I stood side by side and shot the same scene with the same aperture we would get the same scene exposure +- variances in software exposure preferences of the two systems. DOF, though, would not be the same

This is an issue of "Equivalence"

Your m4/3 sensor is equal in per surface area light gathering as an APS-C, or FF.

Assume your trying to take an identical photo on a FF and a m4/3.

The light rays need to bend more to achieve the same image on the smaller sensor.  Thus the required Lens = FF Focal Length/Crop Factor.

To match the DOF of the full frame camera the Aperture similarly need to be reduced, Aperture = FF Aperture/ Crop Factor.

To match the light levels, the Equivalent ISO also need to be adjusted, ISO = ISO/(Crop Factor)^2.  This is really the surface area ratio.

If the Full Frame is 50mm, f/16, ISO 100

APS-C is 33mm, f/11, ISO 234

m4/3 is 25mm, f/8, ISO 400

1" is 18.5mm, f/5.9, ISO 740

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PostTue Apr 28, 2020 6:02 pm 
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Camera smack-talk, while a bit dry, is good entertainment and bit educational.

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PostWed Apr 29, 2020 7:40 am 
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InFlight wrote:
gb wrote:
This is a misconception. Just because a FF camera has a bigger sensor and captures more total light, does not mean it captures more light per unit area of the sensor. If you and I stood side by side and shot the same scene with the same aperture we would get the same scene exposure +- variances in software exposure preferences of the two systems. DOF, though, would not be the same

This is an issue of "Equivalence"

Your m4/3 sensor is equal in per surface area light gathering as an APS-C, or FF.

Assume your trying to take an identical photo on a FF and a m4/3.

The light rays need to bend more to achieve the same image on the smaller sensor.  Thus the required Lens = FF Focal Length/Crop Factor.

To match the DOF of the full frame camera the Aperture similarly need to be reduced, Aperture = FF Aperture/ Crop Factor.

To match the light levels, the Equivalent ISO also need to be adjusted, ISO = ISO/(Crop Factor)^2.  This is really the surface area ratio.

If the Full Frame is 50mm, f/16, ISO 100

APS-C is 33mm, f/11, ISO 234

m4/3 is 25mm, f/8, ISO 400

1" is 18.5mm, f/5.9, ISO 740

But this is all irrelevant in shooting any particular image, because the base ISO for any particular system and the system design is set to maximize performance - i.e. Dynamic range and noise, etc. So, m4/3 at designed base ISO and a given aperture will produce the exact same exposure +_ as FF at designed base ISO.

Exposure and aperture on different systems

Cambridge in color on comparing sensor sizes
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InFlight
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PostWed Apr 29, 2020 12:50 pm 
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Try reading from sources other than Cambridge in Color

https://www.dpreview.com/articles/2666934640/what-is-equivalence-and-why-should-i-care

https://www.spiedigitallibrary.org/journals/optical-engineering/volume-57/issue-11/110801/Equivalence-theory-for-cross-format-photographic-image-quality-comparisons/10.1117/1.OE.57.11.110801.full?SSO=1

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gb
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PostWed Apr 29, 2020 4:15 pm 
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But this is all irrelevant in shooting any particular image, because the base ISO for any particular system and the system design is set to maximize performance - i.e. Dynamic range and noise, etc. So, m4/3 at designed base ISO and a given aperture will produce the exact same exposure +_ as FF at designed base ISO.

Exposure and aperture on different systems (see above link)

Cambridge in color on comparing sensor sizes (see above link)
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InFlight
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PostWed Apr 29, 2020 5:03 pm 
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gb wrote:
But this is all irrelevant in shooting any particular image, because the base ISO for any particular system and the system design is set to maximize performance - i.e. Dynamic range and noise, etc. So, m4/3 at designed base ISO and a given aperture will produce the exact same exposure +_ as FF at designed base ISO.

I've provided some references if your open to learning about photography equivalency.  Otherwise your entitled to your own belief, even if it is not supported by any actual physics.

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PostWed Apr 29, 2020 6:44 pm 
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InFlight wrote:
I've provided some references if your open to learning about photography equivalency.  Otherwise your entitled to your own belief, even if it is not supported by any actual physics.

This is a laughable attempt to pump yourself up. If that is what you need go for it.

I'll just go on shooting with the gear I've used for 6 years and try to learn to be a good birder.
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PostWed Apr 29, 2020 7:38 pm 
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InFlight wrote:
https://www.spiedigitallibrary.org/journals/optical-engineering/volume-57/issue-11/110801/Equivalence-theory-for-cross-format-photographic-image-quality-comparisons/10.1117/1.OE.57.11.110801.full?SSO=1

I am going to have to deep read that!
Thanks for sharing the link.
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PostWed Apr 29, 2020 7:55 pm 
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InFlight wrote:
To match the DOF of the full frame camera the Aperture similarly need to be reduced

This makes sense to me.  No way around it if you want the end result to have equivalent DOF.

InFlight wrote:
To match the light levels, the Equivalent ISO also need to be adjusted

Wouldn't the "need" vary by scene?  For example, if shooting a static scene couldn't you just take a longer exposure at lower ISO to achieve the equivalent light levels?
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InFlight
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PostWed Apr 29, 2020 9:08 pm 
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Tom wrote:
Wouldn't the "need" vary by scene? For example, if shooting a static scene couldn't you just take a longer exposure at lower ISO to achieve the equivalent light levels?

If it was a static landscape and clear sky, a few stops wouldnt make a difference.  If there is water movement, or clouds blowing than its a different discussion.  The shutter speed is therefore not changed with equivalence.

Other than an academic discussion; one of the key points is wide apertures on crop sensors are effectively reduced.  On a m4/3, that $600 Leica 17mm f1.7 is really effectively a 34mm f/3.4.  So crop sensors apertures are a lot of false advertisement.

Both Canon EF and Nikon F have $600 35mm f/2.

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PostThu Apr 30, 2020 12:32 am 
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InFlight wrote:
gb wrote:
This is a misconception. Just because a FF camera has a bigger sensor and captures more total light, does not mean it captures more light per unit area of the sensor. If you and I stood side by side and shot the same scene with the same aperture we would get the same scene exposure +- variances in software exposure preferences of the two systems. DOF, though, would not be the same

To match the DOF of the full frame camera the Aperture similarly need to be reduced, Aperture = FF Aperture/ Crop Factor.

To match the light levels, the Equivalent ISO also need to be adjusted, ISO = ISO/(Crop Factor)^2. This is really the surface area ratio.

It's almost like you two are having an argument about two separate subjects.  wink.gif

The Light Value (LV) of your subject is the same regardless of which camera you point at it. An exposure value (a given combination of ISO/shutter speed/aperture) of that LV is the same regardless of which camera you shoot it on. Shooting LV15 (aka sunny 16) at 1/100 and f/16 at ISO 100 is EV15 regardless of whether your sensor is micro 4/3, 135 (FF), 4x5, etc.

That DPreview link about effective DOF was useful; it's always been clear that smaller sensors produce images with way more DOF for an equivalent field of view (which makes out of focus backgrounds hard on pocket cameras), but it was nice to see the math worked out.

But InFlight's statement above is just that if you want the equivalent image on a crop sensor, you need to 1) use a shorter focal length (eg, a 35mm lens on APS-C looks similar to 50mm on FF), then 2) use a larger aperture (ie, smaller f-number - use f/2.5 on APS-C  to get the equivalent DOF to f/4 on FF), then 3) since you have opened up the aperture, you need to decrease ISO if you keep shutter speed constant.

I think InFlight's math got mixed up in the list of values for different sensor sizes, which is maybe the source of the confusion. Starting with a reference FF exposure, the aperture is getting bigger (ie, the f-number is getting smaller) as you shrink the sensor down to APS-C and below, but the ISO numbers are going up for the smaller sensors in the list when they should be going down. If you use f/11 on APS-C to get the same DOF as f/16 on FF, you would use ISO 50 on APS-C to keep shutter speed the same as with ISO 100 on FF. (1 stop more aperture means 1 stop less ISO.)

From the Equivalence Theory article InFlight cites:

Quote:
For example, consider a focal length f = 24 mm , f -number N = 2.8 , and ISO setting S = 800 on a full-frame camera. According to equivalence theory, in order to obtain an equivalent photo using an APS-C camera, the equivalent settings are f = 16 mm , N = 1.8 , and S = 342 .

APS-C is 1.5x crop from FF. A 24mm lens / 1.5 = 16mm. f/2.8 / 1.5 = f/1.8.
f/1.8 is roughly 1 1/3 stops faster than f/2.8. ISO 800 - 1 1/3 stops is ISO 334 by my math, which is ~ 342 as they give above.

Of course, none of this helps the OP... The problem with bigger sensors is they require bigger lenses (especially if you want a zoom). If you're wiling to carry more glass in order to step up from 1" to APS-C, it looks like there are some pretty high quality mirrorless systems these days, though I haven't used any personally. Portability generally seems inversely proportional with a larger sensor.

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PostThu Apr 30, 2020 8:15 am 
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InFlight wrote:
On a m4/3, that $600 Leica 17mm f1.7 is really effectively a 34mm f/3.4.  So crop sensors apertures are a lot of false advertisement.

Nonsense. F-numbers are simply the ratio of focal length to the diameter of the aperture. So, if the 17mm lens has a maximum aperture of 10mm, it is an f/1.7 lens--  no false advertising involved. Given the same ISO and shutter speed, f/1.7 produces the same exposure on m4/3, full frame, or whatever NASA uses to photograph distant planets.

What you're saying makes a little bit of sense IF your only objective is to achieve minimal depth of field/maximum bokeh at all times, but that's certainly not the only reason someone might want a fast lens (especially for outdoor/landscape pbotography). For that matter, I suppose you could argue that a 40mm f/2 "full frame" lens is effectively 320mm f/16 in relation to an 8x10 view camera, in terms of DOF. But then that makes me think of Ansel Adams lugging his gear into the mountains...  and then stopping down to f/64 because he wanted more depth of field, not less.
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InFlight
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PostThu Apr 30, 2020 8:18 am 
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Equivalence is taking the same photo at the same distance with different camera sensor sizes.  This includes the exact same framing, depth of field, shutter speed, and lightness.

Equivalence Equations

Focal Length (full frame) = Focal Length (crop) * R

Aperture (full frame) = Aperture (crop) * R

ISO (full frame) = ISO (crop) * R^2

Shutter Speed (full frame) = Shutter Speed (crop)

where "R" is the crop factor, the ratio of the diagonal screen sizes

Take away
If your just comparing camera systems and lens, the Focal Length and Aperture equations remain.  You can't look at equivalent focal length in isolation, without the equivalent aperture. 

Makes for some interesting math with cell phone camera's in the 6 to 7 crop factor range.

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