why not f/1.2 by Sony?

Started May 14, 2013 | Discussions thread
S3ZAi
Contributing MemberPosts: 732Gear list
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Re: why not f/1.2 by Sony?
In reply to S3ZAi, May 14, 2013

To OP:

take a look at this thread:

http://www.dpreview.com/forums/thread/3452212

which I started. Exact same thing happened there. My question was almost the same. There were a WHOLE lot of posts saying the exact same thing: it is stupid to ask something like that.

Actually, this kind of post seems to cause a surge of emotional, negative responses. At some point people just kept posting in that thread, just to repeat what others had said, without ever understanding what I was asking. And many without even reading what had been said before. It just becomes easy bashing and people do not shy away from that. Especially the less knowledgeable ones.

There were only a few people, perhaps 1 or 2, who tried to really answer my question. There was only one person who really gave me an answer that was satisfactory and also without misunderstanding or misrepresenting the problem. I will repeat it here, perhaps it will be of value to you: It was posted by Tiago Reil, and he was the only person asking for the reason why I wanted faster lenses, instead of rightaway rationalising away the question. Thanks for that Tiago.

With one more stop of light (or actually 2/3ds of a stop if you consider from 1.8 to 1.4) you gain 2 things:

1-More Light

2-More Shallow DoF.

1-About the first one. There is a big problem with digital sensor that dont get all the light of fast lenses wide open. You can check it youself if you have old fast MF glass, that when you go from f2 to f1.4 you dont actually gain 1 stop of light, but a loss less. that is because in film you used to get rays of light that went transversally, but on digical only perpendicular rays to the sensor are recorded. Some people know this a lot better than me, so I maybe saying things incorrectly, but the empirical idea is there. Get a MF lens, with big aperture and test it. Im Aperture priority, check from 2.8 to 2, and then from 2 to 1.4. See how you dont get a stop of light in shutter speed, but less. This loss is more important with wider apertures (smaller f number). Now a days, it is considered that for ASP-C the sweet spot is 1.8 and for Full Frame is 1.4. Of course some manufacturers come with clever designes to alighn the rays, and dont loose that much, but that costs a lot of money in Research and in glass.  Also, remember that each stop of light, doubles the area that lets light in, so you need more glass. If an optic has 7 elements, each of those elements need to be bigger. IT is more difficult, and a lot more expensive. And gaining 2/3ds of light is not worth it, at least for light, and it is easier to add stabilization, or just be clever and know how to hold the camera.

2-More shallow DoF. LEts see, it is true that you can get more, and that is what we probably want when looking for fast lenses, but again, it is at a big cost. First, it is at a cost, and you can get shallower DoF with other ways. Get a bigger sensor camera. Thats what generally professionals do. Even going to Medium format or plate cameras to get that effect. OR get a longer lens with same aperture. OR get a tilt shift or Lens baby lens to play with that DoF. Those are easier, and more affordable ways to get shallower DoF than going with an ultra big aperture. Manufacturers know this, and this is a balancing act, getting something functional for a faire price. So in general, manufacturers don't care much about that. And, do the calculations. Get how much DoF you get with an extra 2/3ds of a step. Not much. You get a lot more playing with distance, and playing with Focal Length. IT is a big waist of resources for the manufacturers for something easily done other ways.

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Sony Alpha NEX-7 Sony Alpha 7R Sony E 35mm F1.8 OSS Sony FE 55mm F1.8
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