I have a lens technical question!?

86JR

86JR

86JR

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What stops a manufacturer producing a lens like :

18-200mm F2.8 ?

Would it be too heavy or too big or is it simply impossible to make ?

Even 18-70 F2.8 or 16-70 F2.8 etc would be like, "the perfect walkabout lens" but no one produces them, i am wondering why ?

Also for lenses like the 24-70 F2.8, why do they stop at that aperture ? Why do they not make a 24-70 F1.4 etc ?

Help me understand please :)

On a sidenote i think im ordering a 24-70 f2.8 pretty soon im just wondering if 24mm isnt wide enough on a 1.5x crop (some say its perfect some say its not wide enough etc), im just waiting untill im adept enough to use it properly (from the advice in my last thread).

Oh and i ordered that "understanding exposure", thankyou pos3s3d :)
 
twoblacklines said:
What stops a manufacturer producing a lens like :

18-200mm F2.8 ?
Click to expand...

That would be a "superzoom". The tele end is more than 10x the wide end.

Canon to a couple of them:

http://www.canon.co.uk/For_Home/Pro...ses/Zoom_Lenses/EF_28-300_f_f3.5-5.6L_IS_USM/

http://www.canon.co.uk/For_Home/Product_Finder/Cameras/EF_Lenses/Zoom_Lenses/EF_35350mm_f3556L_USM/

Not exactly the focal length that you are looking for but the same sort of idea. It is a phoenominal achievement to be able to get that sort of range out of a zoom lens, but they compromise in places to achieve it and part of that compromise is in the aperture.

The 28-300 has a list price of £3290. To take it to f2.8, you are improving by 2 stops at the tele end. Four times as much light. I don't see it arriving on the market for less than 10x the price. £30k.

It would be the most expensive lens in the range yet because it is a superzoom, it wouldn't have the quality. It wouldn't be as sharp as a 28 prime or a 300 prime.

And it would be heavy.

No-one would buy it.

Andrew
 
twoblacklines said:
What stops a manufacturer producing a lens like :

18-200mm F2.8 ?

Would it be too heavy or too big or is it simply impossible to make ?

Even 18-70 F2.8 or 16-70 F2.8 etc would be like, "the perfect walkabout lens" but no one produces them, i am wondering why ?

Also for lenses like the 24-70 F2.8, why do they stop at that aperture ? Why do they not make a 24-70 F1.4 etc ?

Help me understand please :)

On a sidenote i think im ordering a 24-70 f2.8 pretty soon im just wondering if 24mm isnt wide enough on a 1.5x crop (some say its perfect some say its not wide enough etc), im just waiting untill im adept enough to use it properly (from the advice in my last thread).

Oh and i ordered that "understanding exposure", thankyou pos3s3d :)
Click to expand...

Some of the ose lenses exist, some of them could be made but would be too expensive and not offer good quality, some of them would be almost impossible to make.

18-70 F2.8 or 16-70 F2.8 You can just get the Nikon 17-55mm 2.8, close enough to that range that wouldn't notice the difference really. Tokina make a 16-50 to increase the wide end.

An 18-200mm F2.8 would in theory be manufacturable. The 70-200 end already exists in a near perfect form. From the problem is the longer the focal range the hardware the lens is to design, the more compromises are made and the bigger the distortion and aberrations and the more complex the lens gets to cope with these increasing aberrations.
The end result would be a lens that would be very expensive, very heavy and would not offer very good image quality, so who would buy it?

The complexity of a 24-70.1.4 is probably beyond any current design methodologies that can offer viable image quality.


in the end it is the law of physics which mostly denote what is possible, but current manufacturing abilities are important to. The wider the aperture of the lens, the more perfect everything has to be. The longer the zoom the more complexities and compromises the lens must cope with. It is obvious that you can't make a 1000mm 1.4 lens because you can't get away from the fact that the front element will need to be about 1000/1.4 ≃ 700mm big and would weigh many many kilos.
 
I always thought it's down to the physical size of the lens that will become of an issue.
Speaking in terms of 4/3rds, that's half the sensor size of a FF 35mm, Olympus have come up with a 14-35mm f2.0 lens. That is 77mm thread, nearly 1kg for a 4/3rd lens.
Now to physically stop the other lenses down to 2.0 equivalent for a cropped or even FF lens would be quite a bit bigger and thus making it not viable, both in terms of money for sales and physically using it as a 'walk about lens'.

Now to put it to context of an 18-200mm f2.8, that I would think it's about money, physical size and to top it off, too much compromise needed and thus have poorer IQ. That's my opinion anyway. Plus, as mentioned above, prices will be off the roof!
 
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