A pessimist's take on the new Sony lenses

Started Aug 31, 2013 | Discussions thread
OP ottonis Contributing Member • Posts: 765
Re: An unrealistic take on the new Sony lenses

TiagoReil wrote:

Sorry, changed your post from Pessimistic to unrealistic. I think now it is more correct.

First of all, I will tell you that I assume you are sincere, and that my response is also sincere without any intention of attacking you. Maybe just to make some corrections on your needs, etc. I wont assume you are trolling, but I still think you are wrong.

First whats first. Sony will definitively get a 2.8 at one point or another. It wont be soon. There was a rumor of a 50-150 2.8. I think that lens is probable. But a wide to small tele not so much. There are several reasons, but the reality has to do with priorities. And priorities have to do with perceived amount of clients. Sony caters to a lot of clients with the sony nex. People that want small cameras, people that want high IQ, people that want fast primes, people that want small primes, people that use the video emount line of cameras and use lenses for video, people that will buy into the FF line, and of course people that want very big (monstrous in comparison) fast 2.8 zooms. So, what do you think is the biggest market? What do you think it is the priority for Sony? Not the 2.8 zoom crowd. That doesn't mean they wont ever release one. Im sure they will, but they need to fill a lot of more important holes before that. And they are doing so.

So basically, you don't see one yet cause of priorities.

Second, you say several things on your post that are mutually exclusive. You say you wanted the nex cause it entered on your jacket pocket. Well, I doubt the new zeiss f4 will enter your pockets. A 2.8 will be even bigger.

Third you say you would have preferred that it was a bit bigger but 2.8. This shows me you don't understand what a difference of one stop means for light, and for size.

For light, just one stop of light can be a lot or very little. If you are at 1/15 at 70mm you will get movement. If you get one stop, you could get 1/30, still you will record movement on people walking. So basically, if you are getting movement (people walking, etc) with an f4 lens, you will still get it with 2.8.

For size, one think you don't seem to understand, is that one stop means double the area of the max aperture. So basically, take a look at the glass on the front of that f4 lens, and imagine the area as the double of it. That is one stop of light. That is going from 4 to 2.8. Every stop of light you add doubles the surface. Some math:


if A1 * 2 = A2 then

2*PI*r1^2 = PI*r2^2 remove pi from both places, and move the r1 to the other side

2 = r2*r2/(r1*r1) --> 2 = (r2/r1)^2

so... r2/r1 = sqrt(2) = 1.41421356237 lets round it to 1.4! that is how much it grows the radious (or diameter) with every stop of light.

And actually, sqrt(2) is the reason of the f-stop numbers: 1, 1.4, 2, 2.8, 4, 5.6, etc. It is always the last number multiplied by sqrt(2), aprox 1.4

1*1.4 = 1.4

1.4*1.4 =2

2* 1.4 = 2.8

2.8*1.4 = 4

etc (many of these are rounded).

So basically, the diameter of the lens will be 1.4 bigger, and in area (in glass used) exactly double. So you will use exactly double amount of glass in a lens for going from one stop to another. Exactly DOUBLE. And you are asking it to be a bit bigger and get 2.8. Basically, Unrealistic.

Now, this is a lot of theory. There are ways to make it smaller, but it has a limit. IT has to do with the focal length, and different designs to make the real surface smaller than it should be, but still, making a 1 stop fastest lens, means double the amount of glass, double the difficulty, and generally, at least double the price, many times it is more. Specially for a zoom that generally has a lot more elements than a prime. So, that is why what you are asking is unrealistic.

A last thing to consider is that f2.8 is not the light transmission, but the aperture. It gives you an idea of the depth of field, but not of the real light transmitted. Many lenses that have fast aperture, are not that good transmitting actually. Specially if they are zooms. Cause the amount of glass used means that there is a lot of light lost. So basically, if you want fast apertures for light (instead as of DoF) you want primes, that have less elements and less transmission degradation.

This is the reason that people looking for speed look for primes. That is the reason why people that do street photography mostly use primes. They are better for what you want. Sony is not going to make a line of lenses for people that are lazy. that is pretty stupid. I think that what you have right now, and are doing right now, is the right thing. A couple of primes, maybe a f4 zoom later, etc.

So, as you can see, your search is a fool's search. Probably because of lack of photography knowledge. You don't know what is the right tool for what job. It is ok, no one is born knowing. That doesn't mean that there is no place for a 2.8 zoom on the nex line. There is. But not the ones you are asking for. There will be a 2.8, but it is not the priority. The nex FF is probably a bigger priority right now. Probably a tele 2.8 will be the first one and a wide to tele in the future, one year or 2 from now.

Now, after some thought, I think there is another option that you could consider. It is a strange one, but listen to me. A sony Rx1.

Yes, it is a 35mm lens in FF. But remember it has a very good zoom feature that gets it to 50 and 75mm. Yes, digital zoom, not real zoom, but if you think of it, it is cropping it, you end up with the range you are looking for in the nex, and you will end with a crop sensor, the same you yould use on the nex. So, maybe, the RX1 could be great for you.

From this article: http://www.imaging-resource.com/PRODS/sony-rx1/sony-rx1A.HTM

These two comparison images taken from the same location show the power of the Sony RX1's Smart Teleconverter function, which allows for crop-zooming without significant image quality deterioration at a magnification of 1.4x and 2.0x. The RX1 also comes with Clear Image Zoom and Digital Zoom technologies (although if you value your sanity, don't bother trying to figure out the difference between these three options using the manual!). The RX1's 24-megapixel resolution and ultra-crisp lens make crop-magnification much more useful than you might expect.

Maybe it could be the solution for your needs. Still I think that having an interchangeable lens system to use it with just one lens, expect the manufacturer to make you a lens for every need, etc. Is unrealistic, even impossible (evey lens is designed for different situations, different needs) and that actually, that lens is hte 18-210mm, that already is huge, and has a slow aperture. Actually learn what you need for you, be a bit less lazy, and you will be fine.

All this was written with a lot of respect, and trying to help you and not insult you.



Tiago, this is one of the most elaborated and scientific posts I have seen on dpreview. Thank you for taking the time to write this! I appreciate your response a lot, as it has considerably contributed to my understanding of the matter!

I have definitely underestimated the physical constraints of lens design and have thus built up skewed expectations, which - given the limitations you wonderfully explained - could only be disappointed because being not realistic in so many ways.

As you might have seen, I have quite some very fast primes in my gear list, and being quite the cheap guy, it's all affordable lenses. I am quite happy with them, with potential sensor dust and necessity for sensor cleaning being the only really bothering/annoying thing about that.

Considering all things said in this thread and all the insights that I have gained here with regards to the size, pocketability etc of larger f/2.8 zooms that need an adaptor, I guess I'll just stick with my primes for the time being and make my peace with having to change them on my NEx body as needed.

The RX1 is a gorgeous camera that comes extremely close to my desires, considering its low-light capabilities and smart zooms / cropping options. However, I feel that I first need to improve my photography skills a lot before I even start thinking to acquire such a brilliant camera. Right now, I would feel like someone who just got his driving licence and his first car was a Ferrari, haha

But I see your point and I have to admit some considerable mouth-watering and craving when I look at the compactness (yes, it fits into a jacket pocket) and optical brilliance of the RX1.

All things said, I would like to post up a few pics from my gallery just to make my point on why I have been so eagerly wishing for faster (zoom) lenses: Below you will find a few pics taken from a circus show with EXTREMELY fast moving subjects. All pics have been made with a Walimex (=Samyang) 85mm f/1.4 manual focus lens, and all of them have been shot at very fast shutter speeds (I don't remember exactely but it must have been between 1/300-1/800s, in order to freeze the motion of the subjects. Someone else in this thread stated that I could have done the same pics with an f/4 lens if only my technique and skills were better, allowing for slower shutter speeds. This may certainly be true, but those examples show how much fast glass can help a noob to get fast moving / available light pics that he would otherwise never have been able to obtain.

Nex 5N + Walimex 85mm f/1.4

Nex 5N + Walimex 85mm f/1.4

Nex 5N + Walimex 85mm f/1.4

Nex 5N + Walimex 85mm f/1.4

Nex 5N + Walimex 85mm f/1.4

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