Are DX lens advertised focal lens the DX crop lenth or the optical full frame lentgh


TPF Noob!
Jan 12, 2012
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I have shooting a 35mm 1.8G for a while a D90. I just moved up to a D7000 and picked up a 85mm 1.8D for what I thought was a really good deal. I figured I should try and go with FX lens when I can since the day may come where I move up to FX body. My question pertains to mixing and matching DX and FX lens and how to read the focal lengths...

I know that the 85mm 1.8D being an FX lens is optically a 85mm but will act like a ~127.5-129mm on my crop sensor body. What I couldnt figure out for sure is when a lens is DX is advertised do they take in the account the crop factor or is the advertised length strictly the optical spec. Doing research on my 35mm 1.8G it seems that the angle of viewing is the same as 53mm on FX. It sounds like that means that the 35mm 1.8G is still optically a 35mm but acts like a 53 because of the crop factor.

Is this right?
35mm 18G (DX)is optically a 35mm but acts like a 53mm on crop sensor.
50mm 1.8D is optically a 50mm but acts like a 75mm on a crop sensor.
85mm 1.8D is optically a 85mm but acts like a 129mm on a crop sensor.

What I guess it comes down to... If I see a deal on a nifty 50 I want to make sure it length will actually fit between my 35mm DX and a 85mm FX on my D7000 :)
Yes, it will be 50 mm no matter what. I have seen an ad where they put the focal length of the cropped sensor but usually only when they are selling a zoom point and shoot.
thanks.. this is just means I need to keep my eyes out for a nifty 50.. :)

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