Impact of the image circle size on lens design

[Mousecop]

Yes, comparing equivalent apples to apples in this case means using lenses designed each for their own format and to similar IQ standards.

While we can make that case, the reason why I picked those particular examples is precisely because it shows the impact of the image circle, which is what the OP is interested in.

One such lens designed for a larger format and mounted on a smaller one will typically perform worse than a lens of similar cost designed specifically for the smaller format.

Actually, numerous APS lenses with M43 mounts perform quite well; Sigma in particular does very well. Remember, they are mostly avoiding the edges, thus avoiding the areas that tend to be less sharp.

The disadvantage, as noted, is that they are slightly larger and heavier than their native counterparts.

[Petrus]

Why does a thread with a single simple question about "why small image circle lens is not smaller than a large image circle lens with same focal length and relative aperture" take off tangentially to "equivalence" and other totally unrelated matters?

I have also wondered why Zuiko 300mm f/4 is 227 mm long and weighs 1475 grams. New Nikkor 300mm f/4 147mm long and 755 grams! First for M4/3, later for FF. Certainly the construction is different (and flange distance differs), but thinking that smaller sensor means smaller lenses is not quite true. Let's repeat: I am not talking about equivalence, but simply ask why 300mm f/4 lenses built with small image circle are not smaller, as they should be simpler to design.

I made the same observation on another photography site, and naturally somebody replied "of course Zuiko is bigger as it is 600mm equivalent"... Oh yeah...

[Rory]

The new Nikon 300mm uses diffractive optics to allow the lens to further bend the light which permits a shorter lens.

[Telecaster]

Panasonic's micro FourThirds 100–400mm is smaller in diameter than both my v1 Nikon 80–400mm and FourThirds (not micro) Olympus 50–200mm. The latter two also feel heavier than the 100–400. The Pany isn't a fast lens and so doesn't need very large elements or a large barrel. It's still big & heavy for an m43 lens, yet a fraction of the size & weight (& cost) of a Sigma 300–800mm. The Nikon is similar in speed to the Pany but needs to cover the 35mm-format frame while the Olympus provides less reach but is faster.

-Dave-

[SZRitter]

Why does a thread with a single simple question about "why small image circle lens is not smaller than a large image circle lens with same focal length and relative aperture" take off tangentially to "equivalence" and other totally unrelated matters?

I have also wondered why Zuiko 300mm f/4 is 227 mm long and weighs 1475 grams. New Nikkor 300mm f/4 147mm long and 755 grams! First for M4/3, later for FF. Certainly the construction is different (and flange distance differs), but thinking that smaller sensor means smaller lenses is not quite true. Let's repeat: I am not talking about equivalence, but simply ask why 300mm f/4 lenses built with small image circle are not smaller, as they should be simpler to design.

I made the same observation on another photography site, and naturally somebody replied "of course Zuiko is bigger as it is 600mm equivalent"... Oh yeah...

I think it is probably more due to engineering, patents, and choices made than a "can we". Theoretically, there is no reason the Olympus couldn't match the Nikkor in size. But then you need to start thinking about the type of optics used, motors used, how much time they wanted to invest in engineering, manufacturing costs, and the list goes on. It's easy to armchair quaterback the choices made, but without a view of the entire decision tree that went into this.

One thing to consider, is that the Olympus is branded as a "Pro" lens, meaning they probably wanted little to no sacrifice in the optics ability to render the scene. In the Nikkor, you still have the 300mm f2.8, so Nikon could, hypothetically, cut a few corners on the F4 and not worry as much.

EDIT: The optics may be a bad example, as I don't actually know how good the Nikkor's optics are compared to the Olympus. But, the point still stands.

[Rory]

Olympus markets their system as being smaller and lighter but their telephotos are not.  However, the original question was if it is possible to make a smaller lens of the same focal length and aperture for 4/3 vs full frame ignoring equivalence issues.  That does not appear to be the case contrary to intuition.

[Telecaster]

However, the original question was if it is possible to make a smaller lens of the same focal length and aperture for 4/3 vs full frame ignoring equivalence issues.  That does not appear to be the case contrary to intuition.

Just a two-sample set:

Nikon 80–400/4.5–5.6 (v2) — 91x171mm, 1360g.
Panasonic/Leica 100–400/4.0–6.3 — 83x171.5mm, 985g.

The size difference is minimal on the surface, but note the weight difference. The Pany has smaller diameter elements. Less glass, less weight.

[Edit: the Nikon lens specs above are for v1 of the lens (the version I own), not v2. SZRitter's post below has the correct v2 specs.]

-Dave-

[SZRitter]

Just a two-sample set:

Nikon 80–400/4.5–5.6 (v2) — 91x171mm, 1360g.
Panasonic/Leica 100–400/4.0–6.3 — 83x171.5mm, 985g.

The size difference is minimal on the surface, but note the weight difference. The Pany has smaller diameter elements. Less glass, less weight.

-Dave-

Nikkor 80-400mm/4.5-5.6 (for F-Mount, 35mm) -- 96.5 x 203.2mm, 1570g - Lens on B&H

So, considerably bigger than the PanLeica. It's all about the choices made to produce the lens. The only way to definitively prove this is by having a scientist/engineer speak on the physics limits involved in making the different focal lengths.

[degrub]

and perhaps the weight difference is influenced by Panasonic's propensity to use software to correct optical aberations instead of glass.