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01-22-2019, 04:45 AM - 1 Like   #811
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QuoteOriginally posted by Rondec Quote
We have had long discussions on the forum about "equivalency." Which is to say that if you want to take a photo with one size sensor the is exactly the same as one another size you have to change everything. So, a shot taken at iso 100, 135mm, 1/200 second and f2.8 on APS-C is roughly equivalent to a shot taken at iso 200, f4, 1/200 second and 200mm on full frame. Noise and dynamic range and depth of field should all be the same.
Yes, I know about those discussions. I'm not trying to get an exact match - I'm not interested in "subject isolation" or a certain level of noise - just good photos.

01-22-2019, 04:08 PM   #812
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Ignoring the fact that the point with a larger sensor is to collect more light than a smaller one leads some astray...
01-22-2019, 04:10 PM - 2 Likes   #813
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QuoteOriginally posted by Pål Jensen Quote
Ignoring the fact that the point with a larger sensor is to collect more light than a smaller one leads some astray...
The ultimate point is to record an appropriate image.

Last edited by reh321; 01-22-2019 at 05:56 PM.
01-22-2019, 05:57 PM - 1 Like   #814
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QuoteOriginally posted by Pål Jensen Quote
Ignoring the fact that the point with a larger sensor is to collect more light than a smaller one leads some astray...
The same amount of light hits the sensor at a given exposure regardless of the sensor size. That is why light meters work.

Read the ISO documents on light sensitive sensors. From Wikipedia:
"In photography, exposure is the amount of light per unit area (the image plane illuminance times the exposure time) reaching a photographic film or electronic image sensor, as determined by shutter speed, lens aperture and scene luminance. Exposure is measured in lux seconds, and can be computed from exposure value (EV) and scene luminance in a specified region."
emphasis mine.

Nowhere in the ISO documents does it mention the physical size of the sensor. A 135 format lens will be larger than a ASP-C lens with the same aperture range will be larger not because it inherently "gathers more light" but because the image circle is larger. When you get down to the "light per unit area" the amount of light, number of photons (or whatever you want to call it) will be identical when using a 135 format lens on a APS-C sensor.

If you have a smaller sensor, why would you fabricate a lens that projects the image over a larger area?

While a 135 lens does gather more photons in general, when placed on a APS-C camera body a lot of those photons never hit a sensor and are thus for all intents and purposes are ignored by the camera. Remember, exposure is determined at the surface of the sensor, not the size of the sensor or lens.

01-22-2019, 10:11 PM   #815
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QuoteOriginally posted by PDL Quote
The same amount of light hits the sensor at a given exposure regardless of the sensor size. That is why light meters work.
Light meters measure light intensity, which is "light per unit area".

The amount of light a sensors capture is light per unit area × area size. So at the same exposure a larger sensor captures more light. Which is why a larger sensor tend to give less noise in images at the same ISO as a smaller sensor.

QuoteQuote:
Read the ISO documents on light sensitive sensors. From Wikipedia:
"In photography, exposure is the amount of light per unit area (the image plane illuminance times the exposure time) reaching a photographic film or electronic image sensor, as determined by shutter speed, lens aperture and scene luminance. Exposure is measured in lux seconds, and can be computed from exposure value (EV) and scene luminance in a specified region."
emphasis mine.

Nowhere in the ISO documents does it mention the physical size of the sensor. A 135 format lens will be larger than a ASP-C lens with the same aperture range will be larger not because it inherently "gathers more light" but because the image circle is larger. When you get down to the "light per unit area" the amount of light, number of photons (or whatever you want to call it) will be identical when using a 135 format lens on a APS-C sensor.

If you have a smaller sensor, why would you fabricate a lens that projects the image over a larger area?

While a 135 lens does gather more photons in general, when placed on a APS-C camera body a lot of those photons never hit a sensor and are thus for all intents and purposes are ignored by the camera. Remember, exposure is determined at the surface of the sensor, not the size of the sensor or lens.

Last edited by Fogel70; 01-23-2019 at 01:24 AM.
01-22-2019, 10:22 PM - 3 Likes   #816
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QuoteOriginally posted by Fogel70 Quote
Light meters measure light intensity, which is "light per area unit".

The amount of light a sensors capture is light per area unit × area size. So at the same exposure a larger sensor captures more light. Which is why a larger sensor tend to give less noise in images at the same ISO as a smaller sensor.
No, this is the infamous 'Total Light' fallacy. It was rampant on DPR at one time.

The actual 'sensor' by that physics meaning is the pixel.

The wafer the pixel is on is a different size between the K-1 and the K-5, but the light gathering ability (electron well capacity) is identical in each of the K-5's 16 megapixels to those of the K-1's 36Mp.

The so-called 'pixel pitch' (an indicator of area) for both is around 5 microns.

Last edited by clackers; 01-23-2019 at 01:33 AM.
01-22-2019, 11:48 PM   #817
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QuoteOriginally posted by Pål Jensen Quote
Ignoring the fact that the point with a larger sensor is to collect more light than a smaller one leads some astray...
Yes, sure. If we really want to know the pros/cons of formats against each other, it''s a very complicated equation: lens speed, pixel size, sensor size, depth of field, tripod or hand held. If we would represent image quality on a 2D chart, each format would have an area of overlap onto the next format. Full frame would be the format that cover the largest area of all formats because there are full frame lenses that are as fast as the fastest lenses available for smaller format.

01-23-2019, 01:38 AM - 2 Likes   #818
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QuoteOriginally posted by clackers Quote
No, this is the infamous 'Total Light' fallacy. It was rampant on DPR at one time.

The actual 'sensor' by that physics meaning is the pixel.

The wafer the pixel is on is a different size between the K-1 and the K-5, but the light gathering ability (electron well capacity) is identical in each of the K-5's 16 megapixels to those of the K-1's 36Mp.

The so-called 'pixel pitch' (an indicator of area) for both is around 5 microns.
No, nothing in the post I quoted imply that by sensor it mean pixel. I know you want to use you own invented physics, but most of us prefer to keep to the physics defined by science.

But for exposure there is no difference between sensor and pixel as they both capture the same amount of "light per unit area" in the same exposure.
This is why it is important not to mix "amount of light" with "amount of light per unit area" because they mean two different things.

"amount of light" is the sum of the light captured. Which increase with the captured area.
"amount of light per unit area" is the average light within the captured area. Which only change with intensity of light.
01-23-2019, 03:38 AM - 4 Likes   #819
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Can we just say that larger sensors tend to have more dynamic range and less noise at a given iso and leave it at that?
01-23-2019, 03:53 AM - 4 Likes   #820
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QuoteOriginally posted by Rondec Quote
Can we just say that larger sensors tend to have more dynamic range and less noise at a given iso and leave it at that?
It's out of topic, but format equivalence could be a new thread that we keep for when Adam will offer a K1 II to win if the number of posts reach a certain target. (Usually, when format equivalence discussion starts, lot of ink is being consumed).
01-23-2019, 04:10 AM - 7 Likes   #821
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QuoteOriginally posted by biz-engineer Quote
It's out of topic, but format equivalence could be a new thread that we keep for when Adam will offer a K1 II to win if the number of posts reach a certain target. (Usually, when format equivalence discussion starts, lot of ink is being consumed).
I've never found these sort of discussions particularly helpful. It often seemed to come down to someone who was a full frame evangelist proving that it was the best format because no other size sensor has as wide equivalent aperture lenses available for it. And if the goal of photography is to shoot lenses wide open, I'm afraid I've failed many times. Nearly all of the photos I take, including portraits of my kids, are stopped down a bit.

I think where equivalence was helpful was when people who were familiar with 35mm lens behavior started shooting digital with a smaller sensor, or vice versa, when people who were used to crop sensors started shooting with a larger sensor. In all honesty, I don't think about it at all. If I am shooting with my K3 or my K-1, I just choose a lens and then frame and shoot. It seems to work for me.
01-23-2019, 09:23 AM - 1 Like   #822
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QuoteOriginally posted by Rondec Quote
I've never found these sort of discussions particularly helpful. It often seemed to come down to someone who was a full frame evangelist proving that it was the best format because no other size sensor has as wide equivalent aperture lenses available for it. And if the goal of photography is to shoot lenses wide open, I'm afraid I've failed many times. Nearly all of the photos I take, including portraits of my kids, are stopped down a bit.
By their logic, we should all be using medium format.


QuoteOriginally posted by Rondec Quote
I think where equivalence was helpful was when people who were familiar with 35mm lens behavior started shooting digital with a smaller sensor, or vice versa, when people who were used to crop sensors started shooting with a larger sensor. In all honesty, I don't think about it at all. If I am shooting with my K3 or my K-1, I just choose a lens and then frame and shoot. It seems to work for me.
I use zoom lens, but my logic is the same. Zooming, I never think in terms of focal length, unless curiosity causes me to look afterwards.
01-23-2019, 09:25 AM   #823
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QuoteOriginally posted by Rondec Quote
Can we just say that larger sensors tend to have more dynamic range and less noise at a given iso and leave it at that?
Some people think that throwing numbers at a problem proves something.
01-23-2019, 09:29 AM - 3 Likes   #824
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QuoteOriginally posted by biz-engineer Quote
It's out of topic, but format equivalence could be a new thread that we keep for when Adam will offer a K1 II to win if the number of posts reach a certain target. (Usually, when format equivalence discussion starts, lot of ink is being consumed).
"Equivalence" discussions generate a lot more heat than light {ironically enough}
01-23-2019, 10:42 AM   #825
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QuoteOriginally posted by reh321 Quote
By their logic, we should all be using medium format.


I use zoom lens, but my logic is the same. Zooming, I never think in terms of focal length, unless curiosity causes me to look afterwards.
Actually, using equivalency, 35mm is better than medium format digital as the lenses are faster at equivalent focal lengths.
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