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A bit confused with crop factor and Equivalent magnification

 
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austrokiwi1



Joined: 14 Sep 2014
Posts: 265

PostPosted: Tue Sep 20, 2016 9:58 pm    Post subject: A bit confused with crop factor and Equivalent magnification Reply with quote

I was reading about the new Olympus' MFT 30mm macro lens in a french language article. I was stunned to read that the lens had a maximum magnification of 2.5-1. My French isn't that reliable, so I then searched for more reviews and found the same thing being said in English. Given the price(US$299) of the yet to be released lens I had the distinct impression that the lens was just too cheap to really be a 2.5-1 lens. Finally I gained some clarification on the Olympus website.

".................Thanks to the best-in-class maximum magnification of 2.5x (35mm equivalent) ..........................."

I have smiled a bit when watching one video on U tube. The Author of the video stated he thought a Sony A 7"x" camera was the best because his "X" length prime lens could become an 1.5X lens when he set the camera to APSc. I smiled because my understanding is that an "X" focal length lens stays X no matter what the sensor size is.

I would expect the same applies with magnification. Meaning that it is not appropriate to apply the field of view equivalence ( crop factor) to magnification. It would be nice if someone can confirm this.

As far as my understanding goes the new MFT 30mm macro actually has a maximum magnification of 1.25-1 ( 2.5/ crop factor of 2) which is definitely interesting and shouldn't have required exaggeration.


Camera manufacturer's or their marketers seem, to me, to be really stretching reality at times.
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johan



Joined: 06 Sep 2011
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PostPosted: Wed Sep 21, 2016 3:07 am    Post subject: Reply with quote

Yeah, the inaccuracies marketers introduce do border on the slightly ridiculous.

Reproduction ratio does not change with a different sensor. The degree of magnification depends on focal length and subject distance and sensor size does not change this. Personally I think that even the notion of lens focal length and its APSC "equivalence" is a bit iffy, marketing claptrap (and I'm a marketer myself!)
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ChrisR
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PostPosted: Wed Sep 21, 2016 3:57 am    Post subject: Reply with quote

It obviously distorts 1.25:1 to 2.5:1
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austrokiwi1



Joined: 14 Sep 2014
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PostPosted: Wed Sep 21, 2016 8:09 am    Post subject: Reply with quote

Quote:
It obviously distorts 1.25:1 to 2.5:1


Twisted Evil Twisted Evil Twisted Evil Twisted Evil Twisted Evil ROFLMAO
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Still learning,
Cameras' Sony A7rII, OLympus OMD-EM10II
Macro lenses: Printing nikkor 105mm, Sony FE 90mm F2.8 Macro G, Schneider Kreuznach Makro Iris 50mm , 2.8, Schnieder Kreuznach APO Componon HM 40mm F2.8 , Mamiya 645 120mm F4 Macro ( used with mirex tilt shift adapter), Olympus 135mm 4.5 bellows lens, Oly 80mm bellows lens, Olympus 60mm F2.8
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ray_parkhurst



Joined: 20 Nov 2010
Posts: 756

PostPosted: Wed Sep 21, 2016 3:36 pm    Post subject: Reply with quote

austrokiwi1 wrote:
Quote:
It obviously distorts 1.25:1 to 2.5:1


Twisted Evil Twisted Evil Twisted Evil Twisted Evil Twisted Evil ROFLMAO


Agreed. Not at all helpful, unless the 30mm has shift capability. Wink
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rjlittlefield
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Joined: 01 Aug 2006
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Location: Richland, Washington State, USA

PostPosted: Wed Sep 21, 2016 9:04 pm    Post subject: Re: A bit confused with crop factor and Equivalent magnifica Reply with quote

Quote:
".................Thanks to the best-in-class maximum magnification of 2.5x (35mm equivalent) ..........................."

Despite my pickiness about precision, I actually have some sympathy for people who use "35mm equivalent" like this.

The problem with not using "35mm equivalent" is that, without it, understanding the lens spec becomes an exercise in juggling the lens numbers in conjunction with the sensor size.

As an example, the labeling on the lens of a camera in front of me at this moment says "5.8-34.8mm 1:2.8-4.8". But the focal length tells me nothing about the field of view unless I also know the sensor size, and that information is not printed on the camera. After looking up the sensor size (5.8x4.3mm -- it's a Canon A710), I can struggle through the math to learn that the horizontal AOV is "35mm equivalent" to a 36-218mm lens, which (given my background) immediately tells me that it goes from somewhat wide angle to pretty good telephoto. That's a fact that I will use much more often than the actual focal length.

The dpreview article that I'm looking at quotes Olympus as saying
Quote:
The new M.Zuiko Digital ED 30mm f3.5 Macro helps users capture unique images with a maximum image magnification of 2.5x (35mm equivalent), the highest in its class. With the minimum focusing distance of 95mm (14mm from the end of the lens) and a minimum shooting field of 13.9 x 10.4mm, the lens enhances the beauty of everyday details like dew on a blade of grass or the eyes of a sleeping baby.

I agree that the Olympus spec could be improved, though it's already better than most.

But given austrokiwi's description, I would criticize most strongly the authors of the review articles, who apparently either did not understand what was being said in the first place, or thoughtlessly changed the meaning by omitting the crucial qualifier.

--Rik
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ChrisR
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Joined: 14 Mar 2009
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PostPosted: Thu Sep 22, 2016 7:02 am    Post subject: Reply with quote

Quote:
field of 13.9 x 10.4mm,
Ah, sanity!

I bought my wife a semi-compact with a 1" sensor. I don't remember now what that means. Not 25.4mm, of course. Lens "25mm - 250mm equivalent" I'm happy with.
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