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06-13-2014, 10:46 PM   #16
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QuoteOriginally posted by OregonJim Quote

"The same total light over a larger area" - again, nonsense. The light reaching a 16mm x 24mm area does not change AT ALL when you switch in a larger sensor. The larger sensor capture more of the lens' projected image circle, that's all. Exposure is exactly the same. That same 16mm x 24mm area in the center does not magically get brighter or dimmer. These guys are bending math and physics to their whim and not even thinking sensibly. Reminds me of statisticians.
Exposure, which can be thought of as light density, is not the same thing as total light.

Think about what you're saying above - if what you said was true, then a f/1.8 lens on an iphone can give you the same exact image as an f/1.8 lens on a FF camera, if the FOVs were equivalent. You know that's not the case.

.

06-13-2014, 10:53 PM   #17
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QuoteOriginally posted by jsherman999 Quote
Think about what you're saying above - if what you said was true, then a f/1.8 lens on an iphone can give you the same exact image as an f/1.8 lens on a FF camera, if the FOVs were equivalent. You know that's not the case.
Why is that not the case? If what you're saying is true, then all light meters on the market are useless. And you know that's not the case.
06-13-2014, 11:15 PM   #18
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QuoteOriginally posted by bxf Quote
All along while reading the various FF related arguments I've been assuming that given the same f-stop/shutter speed/ISO, all formats will produce images of equal brightness. Reading comments from other members leads me to believe that I am not the only one under that impression.

I am slowly reading Joseph James' Equivalence essay, and I am puzzled by the following statement:

The same total light falling on the larger sensor will result in a lower exposure than the smaller sensor (the same total light over a larger area results in a lower density of light on the sensor).

Can anyone explain, please? Is there any relationship between what this means ant my opening statement above?
I can see others in this thread are responding to what they think the above is saying, because it was pulled out of context.

He's describing an equivalent image scenario in which the total light is kept the same because the larger format had to have the lens stopped down, compared to the smaller-format combo. When it's stopped down to reach the same total light on the sensor - achieving the same DOF for the same FOV - then shutter speed is less, and exposure is less. Remember, exposure is not the same thing as total light.

Example, from the same distance to subject:

50mm f/1.8 FF
25mm f/1.8 m43

Same FOV, same f-stop, same shutter speed, same exposure. Different total light on the sensor, though, because the FF combo has a 27.8mm entrance pupil (50 / 1.8) and the m43 combo has a 13.9mm entrance pupil (25 / 1.8) - this different total light results in 2 'stops' less DOF for the same FOV for the FF combo, and about 2 stops less noise (depending on respective sensor efficiency.)

So, to get equivalent images - to describe the relationship between formats, not because you have to get equivalent images (Norm!) - you would stop the FF combo down 2 stops:

50mm f/3.6 FF (50 / 3.6 = 13.9mm entrance pupil)
25mm f/1.8 m43 (25 / 1.8 = 13.9mm entrance pupil)

Giving you the same DOF and total light - but less exposure. If you were shutter-speed constrained, you'd presumably bump the ISO up two stops on the FF system to match shutter speed as well - thus, showing similar image noise as well.

I'll paste the whole context below, hopefully it's more clear that way:




---------- Post added 06-14-14 at 12:17 AM ----------

QuoteOriginally posted by OregonJim Quote
Why is that not the case? If what you're saying is true, then all light meters on the market are useless. And you know that's not the case.
Light meters are concerned with exposure, so you can choose an appropriate shutter speed - they don't directly apply to DOF for the FOV or image noise - for that you have to have a light meter that speaks equivalence.
06-13-2014, 11:26 PM   #19
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QuoteOriginally posted by jsherman999 Quote
Light meters are concerned with exposure, so you can choose an appropriate shutter speed - they don't directly apply to DOF for the FOV or image noise - for that you have to have a light meter that speaks equivalence.
Who was discussing DOF? Last I checked, we were talking about exposure. Particularly f-stops, which don't change based on media size for a given exposure.

06-13-2014, 11:34 PM   #20
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QuoteOriginally posted by OregonJim Quote
Compare it to LCD screens: a 10", 640x480 LCD will be much sharper than a 30", 640x480 LCD at the same viewing distance.

Or printed images - a 4"x6" print is much sharper than an 11"x14" with the same number of pixels (because they are smaller).
Ok, display devices are not capturing devices. Whether or not big or small pixels in a display device are hampered by their bigness or smallness in displaying a pixel faithfully I just don't know, but I do know they are both sent the same information as input so that's a flawed comparison. Whereas bigger pixels on a sensor are BETTER at capturing light faithfully -- lower signal-to-noise ratio, less aberrations from microlenses, etc etc -- they record the world more faithfully because it is harder to do as the pixel sites shrink. That's just physics.

You were talking about resolving power (which to me means more detail) and now you've switched to apparent subjective sharpness as a viewer might perceive it, I'm not sure. Sure a smaller print with the same number of pixels will seem more subjectively "crisp" AT THE SAME DISTANCE, although it will seem equal at an appropriate equivalent distance (Why would you keep the distance constant with a different display size? Makes no sense.) But you wouldn't argue that the smaller print actually held greater detail, I don't think. Whereas the bigger pixels from the bigger sensor DO give you greater detail/resolving power because they more faithfully capture the light. And then there is diffraction -- the smaller sensor is limited to a smaller range of useable f-stops before it will not only be softer than the larger sensor, but much softer. (Look at the Q which gets noticeably soft at only f/5.6 or so...)
06-13-2014, 11:42 PM   #21
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QuoteOriginally posted by jsherman999 Quote
Example, from the same distance to subject:

50mm f/1.8 FF
25mm f/1.8 m43

Same FOV, same f-stop, same shutter speed, same exposure.
This is exactly what the rest of us were saying.

QuoteOriginally posted by jsherman999 Quote
this different total light results in 2 'stops' less DOF for the same FOV for the FF combo
The difference in DOF is due to using lenses of two different focal lengths. That still has nothing to do with sensor size, or 'total light'.

You can continue to subscribe to the equivalence theory if you want, but I'm tired of debating. I'll just continue to use my different format systems in blissful ignorance of equivalence, and wonder why everything still works the way it always has. Off to bed...

Last edited by OregonJim; 06-13-2014 at 11:57 PM.
06-14-2014, 07:49 AM   #22
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QuoteOriginally posted by OregonJim Quote
Do you have a source to back that up? I just explained why it's not as sharp as a smaller sensor.



http://www.drcameraphd.blogspot.com/

---------- Post added 06-14-14 at 07:52 AM ----------

QuoteOriginally posted by OregonJim Quote
110 film, 4x5 sheet film, 35mm film,
We aren't using film any more. The easiest system for film and the best system for digital are not the same IMO. The only reason we're still using f/stops, IMO, is that it was an easy way to figure out exposure back when the sensor (film) was the same between cameras but the area was different.
06-14-2014, 09:56 AM   #23
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QuoteOriginally posted by OregonJim Quote
Who was discussing DOF? Last I checked, we were talking about exposure. Particularly f-stops, which don't change based on media size for a given exposure.
No, we were talking about total light, of which exposure is only a component. More accurately, I think the OP was confusing exposure and total light, and I was trying to point out this distinction. Total light != exposure. Two sensors of equal efficiency receiving the same exposure but different total light will allow the same shutter speed, but show different DOF and noise characteristics in the resulting image.

Forget FF vs apsc, think: P&S vs. aps-c. If you have a P&S with a fixed-length f/2.8 lens on it, and you take a shot with your aps-c combo at the same distance and FOV, at f/2.8 - and say the sensors have equal efficiency - will the images have the same DOF and noise? Exposure is the same, right? They would have different DOF and noise because more total light is getting to the larger sensor, despite the exposure and shutter speed being the same.

---------- Post added 06-14-14 at 10:59 AM ----------

QuoteOriginally posted by OregonJim Quote

You can continue to subscribe to the equivalence theory if you want, but I'm tired of debating. I'll just continue to use my different format systems in blissful ignorance of equivalence, and wonder why everything still works the way it always has. Off to bed...
Think of it this way - even if you don't believe in equivalence, it will still work for you.


Last edited by jsherman999; 06-14-2014 at 10:14 AM.
06-14-2014, 12:32 PM   #24
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QuoteOriginally posted by ElJamoquio Quote
We aren't using film any more. The easiest system for film and the best system for digital are not the same IMO. The only reason we're still using f/stops, IMO, is that it was an easy way to figure out exposure back when the sensor (film) was the same between cameras but the area was different.
Wow... All film is emphatically not the same. Aperture is now obsolete because we're not using film anymore ?!? Wow. Just wow. By the way, we are still using film, but that's beside the point.

Calling upon DrCameraPHD as a source is like asking Congress to hold your wallet. It also explains where you get your viewpoint from.
06-14-2014, 12:37 PM   #25
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QuoteOriginally posted by jsherman999 Quote
Two sensors of equal efficiency receiving the same exposure but different total light will allow the same shutter speed, but show different DOF and noise characteristics in the resulting image.
I don't agree at all, and I'm not the only one, but it's pointless to argue further. Let's revisit this in a year or two and see if 'equivalence' is still around.
06-14-2014, 12:42 PM   #26
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QuoteOriginally posted by OregonJim Quote
Wow... All film is emphatically not the same. Aperture is now obsolete because we're not using film anymore ?!? Wow. Just wow. By the way, we are still using film, but that's beside the point.
Wow!

I know.
Yes.
I know, and as you said, it's so far outside the point it's not even in the field any more.


QuoteOriginally posted by OregonJim Quote
Calling upon DrCameraPHD as a source is like asking Congress to hold your wallet. It also explains where you get your viewpoint from.
Poisoned well?
06-14-2014, 02:04 PM   #27
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Lets look at some image quality shoots from Imaging Resource.
Pentax K-3
Pentax K-3 Review - Image Quality
"ISO 3200 yields good 8 x 10 inch prints, with only a mild trace of noise in shadowy areas of our target".
Nikon D610
Nikon D610 Review: Express Review
"ISO 3200 prints look good up to 13 x 19 inches. High ISO noise is a bit more visible at larger sizes, but at 13 x 19 inches it's more than acceptable. In fact, 16 x 20 renders a very usable wall display print, and we don't usually discuss that size at this ISO. The "grain" here is very similar to what we saw with the D7100: film-like, very finely-grained noise."

The James Joseph article is....
QuoteOriginally posted by Parallax Quote
The simple explanation is that it is BS. A more detailed explanation is: It's BS.
06-14-2014, 03:03 PM   #28
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QuoteOriginally posted by bxf Quote
I am slowly reading Joseph James' Equivalence essay, and I am puzzled by the following statement:

The same total light falling on the larger sensor will result in a lower exposure than the smaller sensor (the same total light over a larger area results in a lower density of light on the sensor).
Actually that sentence is correct.

What is confusing you is the silly concept of "total light" which is nothing any real life photographer tends to care about, as they use exposure only and are not preaching theories.

Imagine sensors as corn fields and light as rain.
Exposure is the "strength of rainfall".
Total light is the "volume of water dropped from the clouds in total expressed in liters".

A small corn field gets equally soaked in water after one hour of medium rainfall as a double size corn field. So they look equally muddy afterwards. = same exposure (to rain)
The total amount of water which fell on the larger field is still twice as much (it collected more raindrops in total). You do need twice as much water in total to soak the twice as large field in a similar way. Obviously it is more expensive to water larger corn fields as watering a small flower pot. If you dropped only the same amount of rainwater in the larger field, it would be less soaked.

This sentence also explains why sensor size is totally irrelevant in most respects as explained by equivalence:
If you put a wide angle converter such as a speedbooster on your lens it acts like a funnel, concentrating all the rain on a smaller area, whereby this piece gets soaked much more, thus easily creating 16mm f/1.0 lenses on APSC (this is what you get when you attach a speedboster-like WAC to a Samyang 24mm F1.4 lens).
The side effect is that resolution on APSC is better than on FF with equivalent lenses then: for a easy proof see here LensRentals.com - Metabones Magic?
QuoteQuote:
As advertised, the MTF 50 increased compared to the same lens on no adapter.
Forget sensor size discussions: It's nearly all only about the lenses. They do the light collection.
And happily today there is not a single FF lens which has no APSC equivalent - due to the simpicity of just adding some light concentrating lenses to it in the form of a wide angle converter. Stack the converter to a Canon 50/1.2 and you get the 35mm f/0.8 lens which lensrentals used.
06-14-2014, 03:10 PM   #29
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You can grow more corn in a field that's 2.25 times as large.

Resolution on APS-C is basically never better than on equivalent-lens FF with any reasonable comparison.

Your source gives us enough info to determine that the 5DMkII will resolve 45% better linearly (110% better spatially) than the APS-C camera without a speedbooster.
It also gives us enough info to determine that the 5DMkII will resolve 70% better linearly (190% spatially) than the APS-C camera with a speedbooster.

Last edited by ElJamoquio; 06-14-2014 at 03:17 PM.
06-14-2014, 03:54 PM   #30
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QuoteOriginally posted by ElJamoquio Quote
... basically never ... with any reasonable comparison.
Sounds like somebody stomping his far too big boots on the floor screaming "I am right and nobody else.".

Lensrentals IMHO is quite a good authority and any smart reader here can decide for himself what
QuoteQuote:
On a Canon 5D Mk II and our lens shot at f/1.4, the MTF50 was 590 line pairs / image height in the center
On the NEX-7 with Speed Booster adapter and shot at f/0.9, it resolved 720 lp / ih in the center,
mean for detail resolving.

I am a firm believer in 720 is more than 590. 22% more actually.
And be aware that this higher APSC resolving comes at an unfair comparison, as the value on the FF was measuring the lens stopped down more (the lens is f/1.2 but was shot at f/1.4).


This wont go aways with any amount of stomping.
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