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 19 mm PCE equivalent focal length at full Shift
msoomro
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 p.1 #1 · p.1 #1 · 19 mm PCE equivalent focal length at full Shift

I am trying to calculate effective focal length when using 19mm PCE and take two shots with full shift in each direction and stitch. Any suggestion? :-)

Thx

Edited on Oct 06, 2017 at 04:43 PM · View previous versions

Sep 25, 2017 at 06:01 PM
Todd Warnke
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 p.1 #2 · p.1 #2 · 19 mm PCE equivalent focal length at full Shift

The calculator is at the bottom of the page.

Peace,

Todd

Sep 25, 2017 at 08:11 PM
ljkamler
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 p.1 #3 · p.1 #3 · 19 mm PCE equivalent focal length at full Shift

Approx. 11.4mm when in landscape orientation and shifting left and right according to this: http://www.cambridgeincolour.com/tutorials/tilt-shift-lenses1.htm

Sep 25, 2017 at 08:52 PM
msoomro
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 p.1 #4 · p.1 #4 · 19 mm PCE equivalent focal length at full Shift

@Todd Warnke and ljkamler: Thanks much. Exactly what I was looking for

Sep 25, 2017 at 09:01 PM
dasams
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 p.1 #5 · p.1 #5 · 19 mm PCE equivalent focal length at full Shift

ljkamler wrote:
Approx. 11.4mm when in landscape orientation and shifting left and right according to this:

Nikon reports the FOV based on the diagonals. For example, the 19 PCE has a 97 deg FOV. Here's the math.

Diagonal of 24x36 sensor is 43.3 mm
Half of that is 21.65 mm
Arc tan of 21.65 / 19 = 48.7 deg
Double that is 97.5 deg

For a shift lens, you no longer have a 3:2 aspect ratio so does it still make sense to use the diagonal? Cambridge says no and the values from their calculator are based on the height or width of the stitched picture, not the diagonal.

For comparison, if you are in landscape mode and shift up and down, the effective focal length is 14.3mm.

Sep 27, 2017 at 06:21 PM
msoomro
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 p.1 #6 · p.1 #6 · 19 mm PCE equivalent focal length at full Shift

@dasams: thanks

Sep 29, 2017 at 05:59 PM

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Craig Collins
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 p.1 #7 · p.1 #7 · 19 mm PCE equivalent focal length at full Shift

You'll do best by taking 3 images; left center and right. Much better correction. I've not yet done this with the 19 (which I hope to be able to get soon [anyone wanna sell me one?]), and it's possible the wide angle distortion will make stitching challenging. But you can do great work with other PC lenses this way. It's a beautiful format, and much less work stitching. The 85PC does a fantastic job. Your proportion is about 2.78:1. Which just happens to match widescreen video format.

Sep 29, 2017 at 08:49 PM
Fred Miranda
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 p.1 #8 · p.1 #8 · 19 mm PCE equivalent focal length at full Shift

I believe the math goes like this:

24x36 (35mm sensor dimension) - 43.3mm diagonal.

1) Portrait orientation - horizontal shift.

48x36 (-12, +12) shift

√(aa + bb)
√(2304 + 1296)
√(3600) = 60mm (diagonal)
60/43.3 = 1.385

19 mm / 1.385 = 13.75mm

**If you want better IQ and use (-10,10) shift, you would get:
44x36
1936 + 1296 = √3232 = 56.85
56.85/43.3 = 1.313
19/1.313 = 14.5mm

______________________________________

2) Horizontal orientation - horizontal shift. (panorama)

36x24

60x24 (-12, +12) shift

√(60x60 + 24x24)
√(3600 + 576)
√(4176) = 64.62mm (diagonal)
64.62/43.3 = 1.492

19 mm / 1.492 = 12.75mm

The calculator from http://www.cambridgeincolour.com seems to be way off.

Sep 29, 2017 at 09:02 PM
dasams
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 p.1 #9 · p.1 #9 · 19 mm PCE equivalent focal length at full Shift

Fred Miranda wrote:
2) Horizontal orientation - horizontal shift. (panorama)

36x24

60x24 (-12, +12) shift

√(60x60 + 24x24)
√(3600 + 576)
√(4176) = 64.62mm (diagonal)
64.62/43.3 = 1.492

19 mm / 1.492 = 12.75mm

The calculator from http://www.cambridgeincolour.com seems to be way off.

Hi Fred:

Cambridge calculates the FOV along the axis, not the diagonal. Using your formulas above, the math is:

60 / 36 = 1.67

19 mm / 1.67 = 11.4 mm

Not everyone will agree that this is the right approach but it's how they set up their calculator. Dave

Oct 01, 2017 at 04:11 PM
msoomro
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 p.1 #10 · p.1 #10 · 19 mm PCE equivalent focal length at full Shift

@Fred Miranda and all: Thanks for all the info and links. Very useful

Oct 01, 2017 at 05:30 PM
Fred Miranda
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 p.1 #11 · p.1 #11 · 19 mm PCE equivalent focal length at full Shift

dasams wrote:
Hi Fred:

Cambridge calculates the FOV along the axis, not the diagonal. Using your formulas above, the math is:

60 / 36 = 1.67

19 mm / 1.67 = 11.4 mm

Not everyone will agree that this is the right approach but it's how they set up their calculator. Dave

Yes, we can calculate this based on the horizontal angle of view but the two definitions won't be equivalent.

According to CIPA guidelines, 35 mm equivalent focal length is to be calculated like this:
“Converted focal length into 35mm camera” = (Diagonal distance of image area in the 35mm camera (43.27mm) / Diagonal distance of image area on the image sensor of the DSC) × focal length of the lens of the DSC.

Oct 01, 2017 at 05:53 PM

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