F stop question - Page 2
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Old 2 Weeks Ago   #11
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Default Re: F stop question

Quote:
Originally Posted by scoundrel1728 View Post

....... comparing image formats of different aspect
ratios, when coming up with an equivalent focal
length multiplier, do you scale the long dimension,
the short dimension, the diagonal, or the image
area? .........
There's no definitive choice except that area is NOT
a option. All other options are about distance vs FL,
image circle diameter, angle of view, etc, which are
all LINEAR measures.

Area is only concerned when paying for sensors or
film, cuz that stuff costs by the square. Area is also
proffered as a blantant bogus concern by marketers
of medium format. They can claim DOUBLE the size
when the linear increase is less than 50%.

I prefer ... personal choice ... to compare long side
measure of rectangles, cuz it matters little to me if
3:4 includes a bit more sky or foreground than 2:3.

If I were verrrrrry portrait oriented, I would always
compare the short side, cuz 2:3 is just gonna wind
up cropped to around 3:4 or 4:5 anywho.

Diagonal IMNSHO is mainly useful re: image circle.
Pictorially, I don't find it helpful with visualizing.

YMMV
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Old 2 Weeks Ago   #12
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Default Re: F stop question

Quote:
Originally Posted by scoundrel1728 View Post
Speaking of which, when comparing image formats of different aspect ratios, when coming up with an equivalent focal length multiplier, do you scale the long dimension, the short dimension, the diagonal, or the image area? That is an issue I haven't been able to come up with a definitive answer on.
Quote:
Originally Posted by Mr. Pickles View Post
Yeah..... I was going to state that you'd get more "height" in the image with the m43, but then I thought "I wonder if that is really true, or if you get more width...or some of both"...
It has occurred to me that you, having gone with a Four-Thirds system, might have easily available the dimensions of the active part of your imager. Even though the active dimensions for APS-C-sized Canon systems vary from model to model, both of my own cameras have the same active dimensions, and full-frame cameras have an active area of 36 mm x 24 mm, give or take a tenth of a millimeter or two. It won't answer the question definitively, of course, but it will give an idea of what the Four-Thirds designers were thinking.

For me, when I choose to - or am forced to - change an image's aspect ratio from the usual 3:2, I more often make it squarer than skinnier, hence am more likely to crop the long dimension than the short one. Hence, I would be more likely to scale from the short dimension than the long one. Scaling from the diagonal or image area would be ways to take both dimensions into account.
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Old 2 Weeks Ago   #13
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Default Re: F stop question

According to this Four-Thirds whitepaper from Olympus, the Four thirds system gets its crop factor from the diagonal.

Direct quote:
Quote:
6. Four Thirds Sensor Specification

Specifies the recording pixel area and others.
The standard diagonal length is 21.63 mm (half that of 35-mm film format).
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Old 2 Weeks Ago   #14
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Default Re: F stop question

`


Quote:
Originally Posted by scoundrel1728 View Post
................
more often make it squarer than skinnier, hence am
more likely to crop the long dimension than the short
one. Hence, I would be more likely to scale from the
short dimension than the long one. Scaling from the
diagonal or image area would be ways to take both
dimensions into account.
According the graphic below, the short side of 4/3 is
83.3% of the short side of APSC. For the cropping
tendencies you describe, 4/3 would have only a 1.2X
crop factor compared to APSC ... for YOUR cropping.


SENSOR SIZES.png
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Old 2 Weeks Ago   #15
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Default Re: F stop question

Actually, somewhat less than 1.2x, seeing as how the short sides on my (Canon 40D and 350D) models are 14.8 mm.
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Old 2 Weeks Ago   #16
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Default Re: F stop question

Didereaux, The sunny 16 has saved me on many occasions. It is one of the first things I was taught and It is still a good starting point as there are many occasions that I prefer manual control.

Greg
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Old 1 Week Ago   #17
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Default Re: F stop question

`


Quote:
Originally Posted by scoundrel1728 View Post
Actually, somewhat less than 1.2x, seeing as
how the short sides on my (Canon 40D and
350D) models are 14.8 mm.

Cool. Thaz a 1.14X crop factor. If I had your
cropping tendencies I'd ditch my Canon and
get an adapter for a Pen-F

Unfortunately, I have the toadall opposite
of your cropping preference :-(

Canon has already demonstrated via their
M-series that they're not IBIS believers, but
I happen to be one. A Sony a6500 is verrrry
pricey, plus the cost of an adapter that will
prolly be troublesome no regardless of how
expensive it may be :-( :-( :-(


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