08-28-2011, 06:13 PM
[quote name='nandadevieast' timestamp='1314543579' post='11107']
The differences in MFT vs APS vs FF...
This is something i would like to know...if someone can help and document it because there are so many different opinions, views.
Like Yakim, i always thought that shooting at similar aperture and iso will you similar shutter speeds...aren't all apertures and all iso's same whatever the format...
regards,
[/quote]
What I wrote is not my opinion, it is just how things work (optically and according to the physics involved). So, basically, you can see that as "documenting".
You are correct that shooting with similar f-value and ISO setting you get similar exposures with similar exposure times.
What you do NOT get, however, is similar exposures of the sensor, nor similar depth of field in the image. Nor a similar noise "profile".
The non-similar exposures of the sensor get taken care of by different amounts of amplification of the captured signal. Hence, use equivalent ISO settings if you want similar noise performance (together with equivalent focal lengths and equivalent fvalues).
Aperture is not the same as f-value... aperture means "opening". It is measured in mm's. f-values like "f2" actually are "f/2" or "1:2", meaning focal length (hence the f) divided by 2 giving the opening size, the aperture.
So, with this 12mm f2 lens, f2 actually means: an aperture of f / 2 -> 12 / 2 = 6mm wide.
This lens then has an apparent aperture (size of hole as seen by the optics) of 6mm and a focal length of 12mm.
An equivalent lens on FF has a focal length of 12 / 0.5 = 24mm (0.5 being the crop factor of 135 format full frame compared to 4/3rds)
or, when we take FF as standard, with the 4/3rds lens then having a 2x crop factor: 12 x 2 = 24mm.
With a 24mm, and a similar aperture of 6mm, this then gives the equivalent f-value: 24 / 6 = f4.
As you see, the same field of view will be captured now, and the same size of "hole" the light gets to pass through (6mm).
The amount of light per square mm will now be the same... but due to the difference in amplification of the signals, the FF lens/sensor combo will get a 4x longer exposure time.
If you take the EQUIVALENT ISO setting, though, you will now get a similar exposure time again.
4/3rds -> FF
equivalent focal lengths: 12mm -> 24mm, gives us similar field of view
equivalent f-values (similar aperture size): f2 -> f4, gives us similar light intensity reaching the sensor surface, gives us similar DOF
Equivalent ISO settings: ISO 100 -> ISO 400, gives us similar exposure times, similar noise performance.
The differences in MFT vs APS vs FF...
This is something i would like to know...if someone can help and document it because there are so many different opinions, views.
Like Yakim, i always thought that shooting at similar aperture and iso will you similar shutter speeds...aren't all apertures and all iso's same whatever the format...
regards,
[/quote]
What I wrote is not my opinion, it is just how things work (optically and according to the physics involved). So, basically, you can see that as "documenting".
You are correct that shooting with similar f-value and ISO setting you get similar exposures with similar exposure times.
What you do NOT get, however, is similar exposures of the sensor, nor similar depth of field in the image. Nor a similar noise "profile".
The non-similar exposures of the sensor get taken care of by different amounts of amplification of the captured signal. Hence, use equivalent ISO settings if you want similar noise performance (together with equivalent focal lengths and equivalent fvalues).
Aperture is not the same as f-value... aperture means "opening". It is measured in mm's. f-values like "f2" actually are "f/2" or "1:2", meaning focal length (hence the f) divided by 2 giving the opening size, the aperture.
So, with this 12mm f2 lens, f2 actually means: an aperture of f / 2 -> 12 / 2 = 6mm wide.
This lens then has an apparent aperture (size of hole as seen by the optics) of 6mm and a focal length of 12mm.
An equivalent lens on FF has a focal length of 12 / 0.5 = 24mm (0.5 being the crop factor of 135 format full frame compared to 4/3rds)
or, when we take FF as standard, with the 4/3rds lens then having a 2x crop factor: 12 x 2 = 24mm.
With a 24mm, and a similar aperture of 6mm, this then gives the equivalent f-value: 24 / 6 = f4.
As you see, the same field of view will be captured now, and the same size of "hole" the light gets to pass through (6mm).
The amount of light per square mm will now be the same... but due to the difference in amplification of the signals, the FF lens/sensor combo will get a 4x longer exposure time.
If you take the EQUIVALENT ISO setting, though, you will now get a similar exposure time again.
4/3rds -> FF
equivalent focal lengths: 12mm -> 24mm, gives us similar field of view
equivalent f-values (similar aperture size): f2 -> f4, gives us similar light intensity reaching the sensor surface, gives us similar DOF
Equivalent ISO settings: ISO 100 -> ISO 400, gives us similar exposure times, similar noise performance.