Pekka Potka's take on the A7R and the EM1

Started Nov 12, 2013 | Discussions thread
Anders W Forum Pro • Posts: 21,468
Re: Pekka Potka's take on the A7R and the EM1

blue_skies wrote:

rrr_hhh wrote:

Peng Bian wrote:

Yeah, along the same line if thought, maybe for those people the rx1 may actually fit the bill better (assuming as you do that they have a lot of disposable income). Since at the tele end the system gets too big and the body advantage is lost, and can't perform wide for legacy lens owners. Even if they come out with a new ff ultrawide it will most likely be much bigger than the legacy counterpart.

Only within the very narrow set of focal lengths concentrated around 35mm is where I see this body having a good value.

I think that you are a little too restrictive here : some legacy RF lenses are quite small. I could happily use my Zeiss Contax G lenses on thus body which would make a fairly light combo : the 90mm F2.8 is a lens smaller and lighter than the Olympus 75mm F1.8; the 45mm F2 is incredibly sharp and would be a top performer and it is smaller than the Panasonic 25mm F1.4. the 28mm F2.8 would get some problems but still be doable from what I have heard. and it is about the size and weight of the 12mm F2. Yes, the 21mm F2.8 will probably be problematic (that remains to test).

Some Voigtländer lenses designs are problematic at the wide end, but not all. They have to be tested. Legacy SLR lenses are smaller than newer ones and their design doesn't create the same problems as RF lenses. So they would be perfect on that body as well, even the wide angle ones.

Very correct, in mirrorless land the lens length, when measured from the sensor plane to the top glass element on the lens, is usually is close to focal length, give or take.

In DSLR land, the lens length can vary a lot, as the entire lens has to be build outside the mirror box, partially dictated by AF and OSS issues. You can see wide-angle lenses and fast aperture lenses grow to unwieldy sizes. This is much less the case on mirrorless formats, regardless of sensor format.

Also, below 100mm most MF legacy SLR lenses (including adapters) and RF lenses are fairly similar in size. (lens length is close to FL).

The benefit of a smaller format sensor is that the crop factor changes the FOV of the lens. E.g. the Olympus 75mm lens converts to a 150mm lens on FF. That is a 2x zoom ratio (or crop factor).

The aperture also converts the same way: the f/1.8 becomes a f/3.6 on FF, so nothing special here. There are plenty of compact 135/2.8 lenses that would outdo the Oly 75/1.8 on FF mirrorless.

Are there? I went over to B&H and searched for 135 and 2.8. I got a single hit for such a lens: The manual-focus Sony 135/2.8 STF (a specialized bokeh lens with more than twice the weight of the Oly 75/1.8).

There is also a misnomer that f/1.8 allows me to shoot 'faster' on the Oly: it ignores the two stops difference that FF brings. In other words, I can shoot f/3.6 at same speed and noise on FF, using the two stops difference that the sensor brings. Doing so makes things equal, and brings no benefit to either format.

No you can't since smaller sensors tend to be more efficient than larger. See here:

and here

A faster lens would benefit FF, but becomes a bigger package. Compactness of lenses benefits the smaller sensor format. But in normal length lenses (20-100mm) the differences are rather small in lens sizes - the real difference is in FOV/crop factor: e.g. I can use a 25mm lens on Oly versus a 50mm lens on FF. The 50mm lens will be physically larger.

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