Telephoto Weight Efficiency

Started 2 months ago | Discussions thread
SilvanBromide Veteran Member • Posts: 5,038
Re: Telephoto Weight Efficiency

vvgogh wrote:

What do you think is a fair way to compare the weight efficiency of different systems and telephoto lenses?

Here is one figure of merit for focal length limited subjects: (System Weight in grams) / [(Focal Length in mm) x (# Pixels)]

System............................................. FOM (Weight)

Fuji X-T30, 70-300mm F 4.5-5.6... 0.124 (963g)
+ 1.4 Extender............................... 0.100 (1,093g)

Sony A7RIV + 70-350mm F4.5-6.3.. 0.0923 (1,296g)
using 40 MP Square Crop

Sony A7RIV + 100-400mm.............. 0.0858 (2,066g)
+1.4 Extender................................... 0.0662 (2,233g)

Sony A7RIV + 200-600mm............... 0.0828 (2,990g)
+1.4 Extender.................................... 0.0624 (3,157g)

The above comparison has the same pixel density. I suppose another factor would be needed if the pixel densities differ.

Do you know of a lower weight efficiency according to that FOM for a telephoto setup than the above?

Interesting approach - at least as an academic exercise.

In practical terms, I'm not sure how useful it is to compare between systems and formats where the features and results will be quite different. Whereas using a FOM index for comparison only really makes sense if all else is equal (and therefore weight is the only or primary consideration).

So I can see it being a way to consider and compare options within the same system and format (such as your last two examples. Otherwise it seems a bit like allotting a score to apples so that you can compare it with the score you've allotted to oranges. Whereas if, like me, you're not particularly partial to oranges, the comparison is rendered largely moot... ; )

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