A Canon RF 16-28mm f/2L USM is coming [CR1]

neuroanatomist

I post too Much on Here!!
Jul 21, 2010
24,376
1,723
My 70-200mm f/2.8L IS II USM, may it rest in peace, had dust between the front element and the one behind it, though it doesn't extend.
Of course. The back of the lens is open, so air (and dust, OMG!) get in. Zooming and focusing move element groups within the lens, and that moves around the air (and dust, OMG!) inside the lens.

Some people seem to think non-extending zooms are hermetically sealed. Lol.
 

SwissFrank

EOS RP
Dec 9, 2018
289
113
Anyway, I'm sure somebody here could do the math and figure out how large the lens would have to be.
Wider than 50mm it's easy to calculate: focal length divided by f-stop gives the size of the "entrance pupil," the hole you see when you hold a lens up and look at a white wall through it going in. So 135 f/2 will have 72mm hole for light to go in, and since the angle of view is narrow the front element needn't be wider than that.

But for wide lenses, there's no formula. 16-28/2 would need at least a 14mm entrance pupil but that's tiny.
Canon makes a point that without the mirror box, they're finding their optimal lens designs are actually smaller front elements and bigger rear elements.

My personal guess is that while there's a night-and-day difference between 400mm f/4 and f/2.8, there won't be much difference between f/2.8, f/2, and f/1.4 on wide-angle zooms. Any enlargement may be due to other factors they're simultaneously addressing, such as minimizing mechanical vignetting by enlarging some elements, or trading compactness for better corrections or something.
 
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uri.raz

EOS 80D
Jan 5, 2016
127
66
What happened to it? Hope it wasn’t the dust that killed it!!
I noticed IS went haywire. Gave it to a service center to fix, they claimed it got hit, and required the IS unit to be replaced + realign all the elements. The price was so high, I decided to buy a new mark III and be done with it.

If I could buy MAC insurance for 7 years, it would have been covered. Alas, around here (read: a backwater vilayet of the Ottoman empire) the longest MAC insurance around here is for 3 years. It is also insured as property with my apartment, but that one would cover the lens only if it was broken / stolen along with the camera, which works fine.
 

Jasonmc89

EOS 80D + 100-400mm mkii
Feb 7, 2019
111
81
UK
I noticed IS went haywire. Gave it to a service center to fix, they claimed it got hit, and required the IS unit to be replaced + realign all the elements. The price was so high, I decided to buy a new mark III and be done with it.

If I could buy MAC insurance for 7 years, it would have been covered. Alas, around here (read: a backwater vilayet of the Ottoman empire) the longest MAC insurance around here is for 3 years. It is also insured as property with my apartment, but that one would cover the lens only if it was broken / stolen along with the camera, which works fine.
That’s too bad. Our house got broken into a few months ago and my old sigma 17-50 2.8 which was sitting on the TV unit was taken. Home insurance payed out for that no problem. Bit of a price difference though of course!
 

SecureGSM

EOS 6D MK II
Feb 26, 2017
1,063
151
Wider than 50mm it's easy to calculate: focal length divided by f-stop gives the size of the "entrance pupil," the hole you see when you hold a lens up and look at a white wall through it going in. So 135 f/2 will have 72mm hole for light to go in, and since the angle of view is narrow the front element needn't be wider than that.
except Sigma 105 / f1.4 Art with 105mm front element size ;)
 

SwissFrank

EOS RP
Dec 9, 2018
289
113
except Sigma 105 / f1.4 Art with 105mm front element size
Right, as an art lens they wanted to reduce vigetting, by making more of the entrance pupil visible from a wider set of angles. Since the entrance pupil moves as you look it from increasingly off-center, the front element has to be wider to take care of that. But by 135/2 angle of view's getting quite tight so the pupil doesn't need to be a full circle from as wide a set of points.

I actually didn't know this Sigma lens, but it illustrates exactly a design concept I myself had come up with on my own. Without looking at specs I'd bet the Sigma has far less gigetting than other fast 100mm's, am I right? And extremely round bokeh circles even in the corners?
 

neuroanatomist

I post too Much on Here!!
Jul 21, 2010
24,376
1,723
except Sigma 105 / f1.4 Art with 105mm front element size ;)
The front element of a telephoto lens must be at least as large as the entrance pupil (focal length / f-number), certainly it can be larger.

All lenses need to fill the entrance pupil with light, of course, but with telephoto designs the entrance pupil is essentially located at the position of the front element.
 

Kannon

I'm New Here
Jul 2, 2019
14
5
Of course. The back of the lens is open, so air (and dust, OMG!) get in. Zooming and focusing move element groups within the lens, and that moves around the air (and dust, OMG!) inside the lens.

Some people seem to think non-extending zooms are hermetically sealed. Lol.
Mine is not open. There's a lens fixed inside, not moving or rotating. lol
 

YuengLinger

EOR R
Dec 20, 2012
2,358
382
Southeastern USA
Without noticing at first, I've gotten sand on the zoom barrel of my 24-70mm f/2.8L II. And then the inevitable grinding noise inside the lens.

Then there are misty, drizzly days when droplets get on the extended barrel and could lead to fungus in the lens.

It's not all about "microscopic" dust. The extending barrel does make the lens more vulnerable, offsetting some of the expected L build advantages.

That said, I've learned to be more careful. Would I prefer all lenses to be internal zoom? Sure! But I wouldn't want Canon to NOT make the 100-400mm just because they couldn't come up with a practical, affordable way to make it exactly the way I want...

And this reminds me of what my first photography teacher said way back in 5th grade (something we've all heard): "Photography is all about compromises."
 
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degos

EOS 80D
Mar 20, 2015
199
122
Of course. The back of the lens is open, so air (and dust, OMG!) get in. Zooming and focusing move element groups within the lens, and that moves around the air (and dust, OMG!) inside the lens.
The internal elements moving don't need to expel or inhale air, though; they can displace the internal air volume through spillage around their rims.

Sealing a fixed-length lens is a magnitude easier than an extending-barrel. lol!
 
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3kramd5

EOS 5D MK IV
Mar 2, 2012
3,040
375
The internal elements moving don't need to expel or inhale air, though; they can displace the internal air volume through spillage around their rims.

Sealing a fixed-length lens is a magnitude easier than an extending-barrel. lol!
If you ever fly with your gear it will breathe anyway.
 

kaptainkatsu

1DX Mark II
Sep 29, 2015
166
62
I might be the odd man out, but what if, instead of 70-xxx, they made something like a 50-140 f/2 lens? It would most assuredly be a great portrait lens, especially if it were sharp and had great bokeh. It would definiately be the king of portraiture or at least royalty in that realm.
I want to see something like this. I shoot a lot of floor gymnastics and 70 is too long when the gymnasts come up close to you. You can crop on the long end so you don't need 200mm
 

kaptainkatsu

1DX Mark II
Sep 29, 2015
166
62
I just got my 100-400Lii last week and it's been a joy to use on the 5Div and EOS R. I've only owned constant aperture lenses until the 100-400Lii, which was my biggest turn-off with it until I used it. It might even replace my 70-200/2.8L IS.


Answer: Extending Barrel L-series lenses; not a concern.
Theres a menu option to simulate constant aperture. On my 1dx2, C.Fn2:Exposure: Same expo. for new aperture. You can have the camera automatically increase the ISO or decrease the shutter speed (or a combination of both) to maintain the same exposure when the aperture changes.
 
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AlanF

Everyone sits in the prison of his own ideas. A E
Aug 16, 2012
5,250
2,275
I noticed IS went haywire. Gave it to a service center to fix, they claimed it got hit, and required the IS unit to be replaced + realign all the elements. The price was so high, I decided to buy a new mark III and be done with it.

If I could buy MAC insurance for 7 years, it would have been covered. Alas, around here (read: a backwater vilayet of the Ottoman empire) the longest MAC insurance around here is for 3 years. It is also insured as property with my apartment, but that one would cover the lens only if it was broken / stolen along with the camera, which works fine.
I was once advised by a financial expert only to insure for events that are very rare and expensive and that you would not be able to cover yourself. Insurance is worthwhile if you are a klutz who breaks things more than average, forgets to lock up or your budget is so tight you don't have the savings on hand to replace. If you are careful, then your insurance premiums have a large factor for the nice profits and running costs of the insurance company and subsidizing the careless klutzes, and you would be far better off putting aside each month the insurance premiums into your own savings. But, having insurance keeps some people happy.
 

kraats

EOS 80D
Oct 9, 2011
100
15
These kinds of lenses are like speciality tools. You don’t need them often, but when you need then, you REALLY need them.
Yes, 70-135 f2 or something like that woud be just right. 15-35, 24-70, 70-135 f2, 100-400. Looks great to me.
 

SecureGSM

EOS 6D MK II
Feb 26, 2017
1,063
151
The front element of a telephoto lens must be at least as large as the entrance pupil (focal length / f-number), certainly it can be larger.

All lenses need to fill the entrance pupil with light, of course, but with telephoto designs the entrance pupil is essentially located at the position of the front element.
Yes, the OP statement was though : needn't be wider than that. Please see the post I have replied to.
I suggested that in many cases front element of a telephoto lens is larger than the formula suggests.
Then, OP went to explain that larger than needed front element is there to reduce vignetting.
I further explained that it was not correct as vignetting levels reduction was only marginal...

However, corner and edge sharpness was dramatically improved for obvious reason
 

uri.raz

EOS 80D
Jan 5, 2016
127
66
I was once advised by a financial expert only to insure for events that are very rare and expensive and that you would not be able to cover yourself.
True, except reality isn't black & white. If my apartment burnt down, I couldn't buy a new camera + 3 lenses all at once, so I added them to the contents insurance. One lens I can buy new out of pocket. What if two or more broke at the same time, e.g. because they were in a car accident?

Insurance is worthwhile if you are a klutz who breaks things more than average, forgets to lock up or your budget is so tight you don't have the savings on hand to replace.
Which is why I don't insure anything else I have, except as part of contents insurance.