Why not a 12-35 F1.8 - F2.8?

Started 8 months ago | Discussions thread
CharlesB58
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Re: Why not a 12-35 F1.8 - F2.8?
In reply to hdkhang, 8 months ago

hdkhang wrote:

CharlesB58 wrote:

Discussions like this often involve people oversimplifying lens design and construction. For a moment, let's lay aside equivalency considerations of FF vs 4/3 (and keep in mind that while the 24-70 f4 FE lens is comparable in size to the Panasonic 12-35, and looks to be a sweet lens for the A7, the 70-200 f4 FE is considerably larger than the Panasonic 35-100 f2.8. So this particular discussion is fairly limited to lower range zooms)

While aperture size at a given focal length is the major factor in lens size, many other factors come into play as well. How many elements in the lens, and of what type of glass? How many aspherical elements are used? What materials are used in the construction and how robust is the build? People have brought up the large size of the SHG 1-35 f2.0 lens. It must be considered that being an SHG lens, it's meant to have a much more durable construction, with higher precision parts and function, than other lenses. It is also as sharp wide open as it is stopped down, something that seldom occurs with fast aperture FF lenses. Many test reports, and practical experience, show that 24-70 f2.8 FF lenses often have to be shot at at least f4 or f5.6 to give the same sharpness and contrast the ZD lens offered at f2.0.

If Olympus wanted to merely make the lens f2.0, with average performance and durability, they probably could have reduced the size of the lens, but they chose not to compromise the goals of the SHG line. Sadly, most people don't understand why the lens the size it is other than thinking it's merely because it's f2.0.

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If you read back at posts made by some of the experts who frequent dpreview you would know that the SHG 14-35 f/2 and 35-100 f/2 lenses are in fact full frame 28-70 f/2.8 and 70-200 f/2.8 designs with a speed booster (wide angle converter) built in. This explains why it is larger and heavier than the full frame equivalents. The size and weight are not due to being built to a higher quality standard - there is no evidence to suggest that they are any better built than the Nikon/Canon etc. f/2.8 zooms.

The speed booster would have allowed Oly to make those lenses f/1.4 zooms but Oly decided to play it safe and limit the lenses to f/4 (which results in f/2 once boosted). This helps send the message of "sharp wide open" when wide open is actually already stopped down by one stop.

If Oly wanted to make a smaller 14-35 f/2 or 30-100 f/2 they would have started with full frame f/4 designs and boosted them one stop instead.

Never heard of this before. Also, depending on the "experts" I would take such an assessment with a large grain of salt, especially since I haven't seen any such assessment from labs that have actually tested the lenses. Not saying this isn't the case, but I have learned to be skeptical of certain "experts" on DPR forums.

I think what we are looking at is a semantics difference or misunderstanding of what a "telecentric" design actually is, perhaps? Most explanations regarding the size of these 2 lenses revolve around the telecentric design being used to increase edge to edge sharpness and performance wide open.

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