There is no magical size/weight advantage

Started Mar 5, 2014 | Discussions thread
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Re: you shouldn't - smaller formats typically have bigger lenses
In reply to olyflyer, Mar 5, 2014

olyflyer wrote:

razormac wrote:

tko wrote:

Nikon 105mm f2.8 Macro (3.3x4.6in) vs Pana 35-100mm f2.8 (2.7x3.9in) again, advantage smaller format

The Nikon is for FF. The Pana is a 2.0 crop. The Panasonic is functionally and practically equivalent to F5.6 on FF.

Imagine that. A F5.6 lens is slightly smaller than a F2.8 lens. Actually, because of the slow speed, the Panasonic should be smaller that it is. It's a rather large lens for F5.6. To put this in context, the Panasonic should have half the front objective diameter, but it only manages to reduce the size by 20%.

Note: For the non-believers in equivalence, F-stop is a ratio scaled to sensor size. Half the sensor size, half the lens size for the same F-stop. Everything scales, and indeed, at the sensor level you get similar performance. BUT the smaller sensor has to be magnified more for the same print size, leading to more visible noise and other aberrations.

So, performance isn't the same between the Nikon and Panasonic - how could it be with half the diameter of the front element? Unless you believe a F2.8 cell phone lens acts just like a F2.8 FF lens.

I've found that for equivalent performance, the smaller formats typically have larger, heavier, and more expensive lenses.

When did the f ratio become camera rather than lens dependant?

Never. ...and that's not what he is saying. Read that underlined part once again, and say what that means to you.

Yes, well... so what?

Ok, I'll bite.

Equivalent  Performance could mean many things.

1) The final Quality of the Captured Image is identical - I've honestly never seen this. Every photo I've ever taken or seen has always been noticeably better on the larger sensor. But, since I know that before hand and choose to use smaller sensor cameras when appropriate, this is not what I would call equivalent.

2) For the same lighting conditions selecting identical aperture and ISO results in the same shutter speed (I tend to shoot Aperture Priority about 80% of the time, and Manual the rest FWIW).  And, I dont find that I have to change my exposure depending on whether I am shooting CX, DX or FX. This is what I would call equivalent performance. f2 gives the same exposure at ISO 800 independent of sensor size, FOV or focal length

3) Identical FOV coupled with identical exposure settings. This obviously will demand different focal length choices, but also us equivalent performance. DOF is obviously what it is for that system

Don't know if this answers you, or particularlly helps. But, you asked.

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