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### AuthorTopic: Question about MF-lenses  (Read 1725 times)

#### Emilmedia

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##### Question about MF-lenses
« on: October 04, 2012, 06:35:49 AM »

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?

#### yaya

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##### Re: Question about MF-lenses
« Reply #1 on: October 04, 2012, 06:51:05 AM »

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

#### ondebanks

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##### Re: Question about MF-lenses
« Reply #2 on: October 04, 2012, 06:53:06 AM »

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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##### Re: Question about MF-lenses
« Reply #3 on: October 04, 2012, 07:01:39 AM »

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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##### Re: Question about MF-lenses
« Reply #4 on: October 04, 2012, 08:15:06 AM »

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.

#### FredBGG

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##### Re: Question about MF-lenses
« Reply #5 on: October 04, 2012, 02:26:44 PM »

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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##### Re: Question about MF-lenses
« Reply #6 on: October 04, 2012, 03:03:59 PM »

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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##### Re: Question about MF-lenses
« Reply #7 on: October 04, 2012, 07:06:27 PM »

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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##### Re: Question about MF-lenses
« Reply #8 on: October 04, 2012, 08:23:09 PM »

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.

#### FredBGG

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##### Re: Question about MF-lenses
« Reply #9 on: October 04, 2012, 09:06:15 PM »

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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