Maybe this is it !!!

Started Sep 3, 2013 | Discussions thread
Anders W Forum Pro • Posts: 21,468
Re: Bring on a logical lens set....

Sergey Borachev wrote:

Anders W wrote:

So is the series I am actually using at the moment, i.e., the same as above but with 20 replacing 17. Although I marginally prefer 17 over 20 if I think about the FL alone, none of the 17s currently available really appeal to me on other grounds . Hence, I stick with 20 as a substitute for 17.

I agree that none of the 17mm's are appealing and that 17mm is a better FL.

On the other hand, 15 would be too far towards the wide end for me to be a good substitute for 17 or 20. The point of 17 (35 mm EFL), as I see it, is that it still works as a "normal lens" (minimal perspective distortion) unless ýou go very close with it while at the same time giving you a bit more leeway than 25 (50 mm EFL) to fit things in when you can't back up any further. At 15 (30 mm EFL), however, I'd say you are really out of "normal lens" territory.

Due to the ever increasing MPs, images from modern cameras can be cropped a lot more and still retain enough quality when compared with those from decades ago, when 35mm became "normal". My understanding is that the perspective distortion in a picture is a function of subject distance and not the FL. Standing at the same distance, a 15mm and a 17mm should be identical in the amount of such distortion produced by their pictures, although the image from the wider lens has to be magnified more to match the size from the 17mm. Is that correct?

Yes that's correct.

My point is that there is some reason for "modernising" the traditional FL thinking. With some sacrifice in quality (which is abundant and still more than adequate, compared to the old days), the 15mm can take the place of the 17mm as the normal wide or can be accepted as the lens to carry around. The advantage is of course a wider view when needed while retaining the 17mm or even the 20mm FOV with a little penalty.

Yes. On the other hand, the quality loss you are talking about (by not going as close with the 15 as you'd like in terms of framing and instead crop slightly in PP) quickly approaches the one we are talking about when comparing the MTF values of the 17/1.8 to those of the 20/1.7. Then you have additional loss of IQ due to noise (smaller sensor area utilized when you crop) on top of that. Your claim that IQ is "abundant and still more than adequate" strikes me as somewhat contradictory to your claim that the optical quality of the 17/1.8 is insufficient.

Another consideration for me here is what the next step toward the WA end would be. There is currently no rectilinear prime wider than 12 for MFT. And a fisheye, even if defished, is nearly twice as wide as the 12, so a big gap. 17 and 12 strikes me as a pretty good combination on the WA side (effectively "normal" plus wide). This conforms to what I used in the film days (35 and 24). 20 and 12 works fine as well. But 15 and 12 would be a bit too densely spaced for my taste given that I'd like to keep the prime collection I carry down to some reasonable number.

I believe this is the reason why we are seeing more fixed lens cameras with 28mm equiv lenses since the film days, e.g. the Ricoh compacts, the Sigma, the latest Nikon etc.

Hard to tell. I really don't know the reasoning behind the choice of 28 mm EFL for some fixed lens cameras. Note also, that other recent fixed lens cameras do stay close to 35 EFL, e.g., the Sony RX1.

Think in terms of 7.5/15/30/60 maybe for a 2x separated set, 60mm already there in the macro and 15mm in the toy lens cap lens so far - now for a real 15mm and hopefully 30mm later.

Then an even better 1.4x separated prime set would become 7.5/11/15/21/30/42/60 in rounded numbers. Nice. I might even stray from zooms if something sensible like that happens.

Regards...... Guy

 Anders W's gear list:Anders W's gear list
Panasonic Lumix DMC-G1 Olympus OM-D E-M5 Olympus E-M1 Panasonic Lumix G Vario 14-45mm F3.5-5.6 ASPH OIS Panasonic Lumix G Vario 7-14mm F4 ASPH +28 more
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