depth of field question

Hey guys, a question just popped up in my head. Probably a silly one but..

If i took a 50mm prime lens designed for cropped sensor and a 50mm prime lens for full frame. And then take the same picture at f1.8 using both lenses on a crop sensor dslr. Will i get roughly the same amount of depth of field???

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just a newbie with a good eye

Yes and no. A 50mm lens is a 50mm lens regardless of what you put behind it, so the DOF doesn't change.

However, on APS-C you are getting the same depth of field with a moderate telephoto lens as you would with a standard lens on FF. The APS-C camera therefore delivers more DOF.

Looked at in reverse, to get a standard view on FF you use your 50mm lens. But for APS-C you use a 35mm lens and therefore APS-C delivers more DOF.

Bigger formats give less DOF, the smaller the format goes you get more DOF.

At the extreme, a Minox "spy camera" uses a 15mm lens to give the field of view of a 50mm on FF. We know 15mm lenses have immense DOF, so the Minox can be fixed focus and give DOF from about 9" to infinity at open aperture.

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Best regards, John

A 50mm 1.8 lens designed for full frame and a 50mm 1.8 lens designed for APS-C sensor would give exactly the same DOF if both are used on an APS-C camera.

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Yves (another one of those crazy Canucks)

As said, you will get exactly the same DOF.

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Pentax K10D + Vivitar 55/2.8 macro + Super Takumar 55/1.8 + SuperMultiCoated Takumar 85/1.8 + SuperMultiCoated Takumar 135/3.5 + SuperMultiCoated Takumar 200/4 + Super Takumar 300/4
Pentax K100D + DA18-55ALII + DA55-300
Pentax K5 + FA31Ltd + M50/1.7 + DFA100WR + M120/2.8 (+ DA18-55WR at occasion)

thanks! i appreciate the replies

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just a newbie with a good eye