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Doing the Math
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Nov 22, 2017 01:33:49   #
SuperFly48 Loc: NE ILLINOIS
 
The attached image was taken with my Nikon D7100 and Nikon 18-200mm DX VR lens. Focal length for this image is 18mm. To duplicate this shot "exactly", except using a full frame DSLR rather than a cropped sensor DSLR, what should the lens focal length be?


(Download)

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Nov 22, 2017 01:48:36   #
Apaflo Loc: Anchorage, Alaska
 
FlyGuy47 wrote:
The attached image was taken with my Nikon D7100 and Nikon 18-200mm DX VR lens. Focal length for this image is 18mm. To duplicate this shot "exactly", except using a full frame DSLR rather than a cropped sensor DSLR, what should the lens focal length be?

To get the same field of view with a FF sensor use a 1.5 * 18mm focal length, or 27mm.

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Nov 22, 2017 03:11:13   #
Doddy Loc: Barnard Castle-England
 
Nice one Flyguy.

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Nov 22, 2017 03:23:20   #
BebuLamar
 
And stop the lens down one stop more.

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Nov 22, 2017 03:37:33   #
blackest Loc: Ireland
 
BebuLamar wrote:
And stop the lens down one stop more.


And raise the ISO 1 stop

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Nov 22, 2017 04:43:08   #
jerryc41 Loc: Catskill Mts of NY
 
FlyGuy47 wrote:
The attached image was taken with my Nikon D7100 and Nikon 18-200mm DX VR lens. Focal length for this image is 18mm. To duplicate this shot "exactly", except using a full frame DSLR rather than a cropped sensor DSLR, what should the lens focal length be?


I bet if you used four different lenses, all at 18mm/27mm, the framing would be different for all of them.

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Nov 22, 2017 05:58:49   #
repleo Loc: Boston
 
Bebulamar- Why stop the lens down one stop? To match DoF?
Blackest - Why raise the ISO 1 stop?

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Nov 22, 2017 06:11:38   #
joer Loc: Colorado/Illinois
 
jerryc41 wrote:
I bet if you used four different lenses, all at 18mm/27mm, the framing would be different for all of them.


Yes since each lens has tolerances they may be different especially when going across brands. Although I would expect that a side by side comparison would be needed for noticeable differences. Focus breathing is an extreme example of this.

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Nov 22, 2017 07:41:00   #
jerryc41 Loc: Catskill Mts of NY
 
joer wrote:
Yes since each lens has tolerances they may be different especially when going across brands. Although I would expect that a side by side comparison would be needed for noticeable differences. Focus breathing is an extreme example of this.


Maybe I'll give this a test today, or tomorrow. "Tomorrow" is a better time to do almost everything.

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Nov 22, 2017 07:47:22   #
SpyderJan Loc: New Smyrna Beach. FL
 
FlyGuy47 wrote:
The attached image was taken with my Nikon D7100 and Nikon 18-200mm DX VR lens. Focal length for this image is 18mm. To duplicate this shot "exactly", except using a full frame DSLR rather than a cropped sensor DSLR, what should the lens focal length be?


I don't know the answer to your question, but that is one spectacular view.

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Nov 22, 2017 07:52:26   #
Apaflo Loc: Anchorage, Alaska
 
repleo wrote:
Bebulamar- Why stop the lens down one stop? To match DoF?
Blackest - Why raise the ISO 1 stop?

To match the noise as well as the DOF.

But the OP only asked about focal length, and all the rest of this is off topic thread hijacking! : - )

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Nov 22, 2017 07:56:02   #
Bill_de Loc: US
 
oops

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Nov 22, 2017 08:16:05   #
blackest Loc: Ireland
 
repleo wrote:
Bebulamar- Why stop the lens down one stop? To match DoF?
Blackest - Why raise the ISO 1 stop?


closing down the lens by one stop would give a similar depth of field, its not a perfect match if you look at a dof calculator, but close enough for most people.

By closing down the aperture by 1 stop you are recording 1 stop less light the image would be 1 stop under exposed
I chose to raise the ISO by 1 stop to compensate the alternative would be to half the shutter speed (1 stop difference).

if the shutter speed was 1/60th then 1/30th would be needed to keep the same exposure. This particular scene it doesn't particularly matter about the shutter speed.

with micro 4/3rds as the original camera at 18mm you would want 36mm on full frame and close down 2 stops and raise the iso 2 stops.

If you flip this on its head trying to match a full frame photo with a crop sensor or m43 camera. The surprising thing is you need a better lens for the smaller format. With 1 and 2 stops difference for each format.

You are also enlarging the negative more which is going to reveal more of a lenses defects e.g chromatic aberration.
It probably is fair to say the larger the format of the negative the less demanding is the Image Quality required from the system, big is beautiful

Heavy not so easy to take to a location but perhaps why people still love the medium and larger formats even 35mm film.

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Nov 22, 2017 08:20:10   #
Apaflo Loc: Anchorage, Alaska
 
blackest wrote:
closing down the lens by one stop would give a similar depth of field, its not a perfect match if you look at a dof calculator, but close enough for most people.

By closing down the aperture by 1 stop you are recording 1 stop less light the image would be 1 stop under exposed
I chose to raise the ISO by 1 stop to compensate the alternative would be to half the shutter speed (1 stop difference).

if the shutter speed was 1/60th then 1/30th would be needed to keep the same exposure. This particular scene it doesn't particularly matter about the shutter speed.

with micro 4/3rds as the original camera at 18mm you would want 36mm on full frame and close down 2 stops and raise the iso 2 stops.

If you flip this on its head trying to match a full frame photo with a crop sensor or m43 camera. The surprising thing is you need a better lens for the smaller format. With 1 and 2 stops difference for each format.

You are also enlarging the negative more which is going to reveal more of a lenses defects e.g chromatic aberration.
It probably is fair to say the larger the format of the negative the less demanding is the Image Quality required from the system, big is beautiful

Heavy not so easy to take to a location but perhaps why people still love the medium and larger formats even 35mm film.
closing down the lens by one stop would give a sim... (show quote)

None of that pertains to the OP. It is all off topic.

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Nov 22, 2017 08:32:07   #
Bill_de Loc: US
 
Apaflo wrote:
None of that pertains to the OP. It is all off topic.


It's all related. If you can't see the relationship that's just a shame. Your posts are not going to change that, so why not just sit back and enjoy watching how the discussion unfolds. Or, if it is not to your liking, go read something else.

--

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