I think the notion of FF = heavier lens may not be true

Started Nov 8, 2013 | Discussions thread
Great Bustard Forum Pro • Posts: 40,751
Re: Not exactly.

EinsteinsGhost wrote:

EinsteinsGhost wrote:

I know I might get some flak for this, but I was just curious about this debate so decided to check out the olympus site.

I know it's not FF, but if the logic is that bigger sensors mean bigger lenses, then it should also be concluded that aps-c lenses will be bigger/heavier than m43.

But after checking the olympus site, their equivalent lenses are heavier. They don't have exact same focal lengths but relatively close.

zuiko 14-54 2.8-3.5 = 440g

fuji 18-55 2.8-4 = 310

zuiko 50-200 2.8-3.5 = 995g

fuji 55-200 2.8-4 = 580g

for comparison, panasonic's closest was the 45-150, but with a slow aperture of 4-5.6 weight = 200g. It's much lighter than both the zuiko and fuji, but has a slower max aperture.

zuiko 35 f3.5 = 165g

fuji 35 1.4 = 187g

panasonic 45 2.8 = 225g

panasonic 25 1.4 = 200g

I know some may not be a direct comparison, but some of them just don't make the same focal length and aperture. What I find interesting is that Fuji is actually the lightest of the bunch, but has a bigger sensor.

It seems to really all boil down to lens design and materials. I think the assumption is also that all else being equal, yes, it glass elements will be bigger to accommodate a larger sensor, but the lens as a whole can still be light by using lighter metals like aluminum and perhaps less glass elements.

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Lenses can also get heavier depending in build quality. Use more plastic, and weight with same optics can go down. Lens for smaller format can take advantage of smaller parts, however.

Then there is the reach aspect. I use 200mm/2.8 on APS-c whereas the same reach on FF would require 300/2.8.

The same "reach" (diagonal angle of view) would require 320mm. But the same DOF and same light projected on the sensor for a given shutter speed would require f/4.5. So, the better comparison to a 200 / 2.8 on APS-C is a 300 / 4 on FF. APS-C still comes out ahead in terms of size and weight, however.

Whole both are FF lens, the 200/2.8 is considerably smaller with same metal build and weighs only a third (about 750g).

Again, compare to a 300 / 4, and that advantage narrows considerably, although the advantage still lies with APS-C.

You dont need same total light to be projected on a smaller sensor.

You do if you want the same noise performance (for equally efficient sensors) and/or DOF.  And if you don't care about that, then you can compare 200mm on APS-C to 300mm on FF, and leave out the f-ratio all together.

Exposure is independent of sensor size.

It is. So is the total amount of light projected on the sensor (depends on the aperture diameter, as opposed to the f-ratio).

Put 200/2.8 on a FF camera, take note of your exposure variables. Turn crop mode on (I understand Canon can't do it, but Sony and Nikon allow it). Do you expect exposure values to be off by a stop?

Here we are:


This section will answer the following four questions:

  • For a given scene, what is the difference in exposure, if any, between f/2.8 1/200 ISO 400 and f/5.6 1/200 ISO 1600?
  • What role does the ISO setting play?
  • What role does the sensor size play?
  • What does any of this have to do with the visual properties of the photo?

As mentioned in the introduction of this essay, the concept of Equivalence is controversial because it replaces the paradigm of exposure, and its agent, f-ratio, with a new paradigm of total light, and its agent, aperture. The first step in explaining this paradigm shift is to define exposure, brightness, and total light.

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