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 Author Topic: Question about MF-lenses  (Read 1438 times)
Emilmedia
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 « on: October 04, 2012, 05:35:49 AM » Reply

So I still havent decided on what camera to go for. I'm still leaning towards a H3DII-39. My question is tho, compared to regular 35mm lenses.

How do i figure out their "mm". For example, the 100 f 2,2 and the 80 2,8 and the 35 mm. What would they be if they were a 35mm lens?
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yaya
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 « Reply #1 on: October 04, 2012, 05:51:05 AM » Reply

So I still havent decided on what camera to go for. I'm still leaning towards a H3DII-39. My question is tho, compared to regular 35mm lenses.

How do i figure out their "mm". For example, the 100 f 2,2 and the 80 2,8 and the 35 mm. What would they be if they were a 35mm lens?

100mm = ~70mm
80mm = ~56mm
35mm = ~25mm

You divide the diagonals of the two formats, which gives you the "ratio" so then you can calculate any equivalent focal lengths
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ondebanks
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 « Reply #2 on: October 04, 2012, 05:53:06 AM » Reply

Multiply by the ratio of the sensor diagonals.

35mm format -> 43mm diagonal

39 MP back -> 60mm diagonal

Ratio = 43/60 = 0.72

So HC 100mm equiv to 72mm on 35mm sensor....etc.

Ray
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MarkoRepse
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 « Reply #3 on: October 04, 2012, 06:01:39 AM » Reply

Same goes for aperture (just not at macro scale)
f2.8 (MF) * 0.72 = f2.0 (35mm)
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Doug Peterson
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 « Reply #4 on: October 04, 2012, 07:15:06 AM » Reply

http://www.digitaltransitions.com/visualizer/visualizer.html

This visualizer will help you SEE the equivalents (including the different aspect ratio).

Use the p45+ in the visualizer. It has the same sensor as an h3d-39.
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FredBGG
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 « Reply #5 on: October 04, 2012, 01:26:44 PM » Reply

Also you need to consider who you crop.

If you are printing 8x10 for example you will be cropping some off your 35mm FF so your effective image diagonal will change.
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RazorTM
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 « Reply #6 on: October 04, 2012, 02:03:59 PM » Reply

8x10 is a 4:5 while the Hassy is a 4:3 sensor, so you'll be cropping there, too.
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ondebanks
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 « Reply #7 on: October 04, 2012, 06:06:27 PM » Reply

Same goes for aperture (just not at macro scale)
f2.8 (MF) * 0.72 = f2.0 (35mm)

Well...yes and no.

For exposure metering, flash reach, etc., aperture stop doesn't scale between formats - those 100 mm and 72 mm lenses give the same results on the two formats we're talking about, if both are set to say f2.8.

But for depth of field (which I think is what you meant), then you do scale it in that manner to find the f-stop which gives matching dof.

Ray
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ErikKaffehr
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 « Reply #8 on: October 04, 2012, 07:23:09 PM » Reply

Hi,

I don't think that real world has 3/2, 4/3, 5/4 or any other crop and I don't think it is natural to let print size decide your crop. Crop to subject.

Best regards
Erik

8x10 is a 4:5 while the Hassy is a 4:3 sensor, so you'll be cropping there, too.
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FredBGG
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 « Reply #9 on: October 04, 2012, 08:06:15 PM » Reply

Hi,

I don't think that real world has 3/2, 4/3, 5/4 or any other crop and I don't think it is natural to let print size decide your crop. Crop to subject.

Best regards
Erik

My point was to take aspect ratio into account when making a lens choice when looking at another format.

For example a photographer that shoots mainly fashion magazines will be working in a crop closer to 5/4.
If that photographer shoots 35mm DSLR he is pretty much always cropping off the top and bottom so the diagonal
he uses to make a focal length conversion should take that into account.
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