Dreaming of EF-S 600mm f/4 IS

[robert5_p]

Dreaming of EF-S 600mm f/4 IS:

This is my first post on this forum. I am an amateur photographer/enthusiast with interest in all kinds of photography, wildlife photography in particular.
I would like to learn what other people think of the idea of EF-S super tele.

So far the EF-S lens mini-series covers the wider focal lengths. It seems like Canon focus is mostly on solving the limitations of 1.6 crop factor dSLRs in wide-angle photography. On each photography forum on the web, I see foresights of full frame censors eventually replacing APS-C and the claims that everyone will want to upgrade to full frame as soon as the price is right.

In my dream the opposite happens: Canon designs a new EF-S lens in the lens category where the 1.6 crop has a clear advantage. EF-S 600mm would clearly change the future outlook of smaller sensor size dSLRs.

It is clear that the extreme 12lbs weight and 7K$ cost of EF 600 f/4L results largely from the physical limitations of f/4 and 36mm wide film/sensor.
So how much lighter and cheaper would the imaginary EF-S 600mm f/4 be?

WEIGHT: Well, who knows, but a 1.6 diameter reduction of 600mm monster should yield quadratic (2.56x) reduction or event cubic (4x) reduction of some lens elements (some lens elements will become thinner as well). Lighter glass should allow less sturdy housing. So we can hope for somewhere around 4lbs! Think handholding 12lbs vs 4 lbs!!!

COST: Canon prices for big gun primes seem to be strongly depended on their weight (I think of their pricing as paying per pound of quality optics).
A 4lb lens should be closer in price range to the 3lb lenses such as 400mm f/5.6 or 300 f/4 IS as and we can hope to be not much more than 2K!

One more point: when most people are happy about 1.6 magnification factor on the tele lenses, I view the magnification as cropping and think of how much of the lens is simply wasted. I am not using roughly 60% of a big lens that I have paid for, as about 60% the lens works to pass the light outside of my small sensor.

GUESS about the FUTURE:
Super tele lenses made for APS-C coverage is exactly what is missing to provide lasting value for smaller sensor dSLRs.

I believe that many wildlife photographers would want to buy a smaller senor camera to take advantage of much lighter and cheaper super-tele lenses (if such are manufactured).
This would probably increase long term dSLR camera sales (many of us would probably save up to buy 1 full frame for landscape, portraits, etc, and one APS-C for super-tele photography.)

On one hand, Canon may (and justly so) be afraid that producing EF-S 600mm would jeopardize sales of their current big guns.

But, on the other hand:

- there are many people like me, who will never spend 7K for a 12lb lens, because it is too expensive AND too heavy; but would buy lighter and somewhat less expensive EF-S.

- there are those who will still buy EF 600mm because
(1) it is an L and excellent piece of glass,
(2) full frame will always yield better picture quality.

- there is always the competition, it is better for Canon to sell cheaper EF-S 600mm and not lose the customer to Sigma, Nikon, or somebody else.
Today’s amateur photographer interested in wildlife has a choice of
- high quality accompanied by HEAVY weight, huge size and very hefty price tag.
- convenience provided by PS zoom accompanied by teleconverter lens (think of Powershot S2 IS with Raynox 2.2x – 950mm equivalent that almost fits into a large pocket!)
There is clearly a good market for something in-between as far as price, weight, size and quality and someone may want to grab that market.

So what does the future hold? I HOPE we will see super-tele EF-S.
And … maybe Canon lens designers will look at this thread and a year from now my dream will be reality… After all this is my dream.

I would love to learn what do YOU think.

[willg]

sounds like a good idea to me, but it seems like canon is pushing the full frame thing more and more. There are certainly benefits of a larger sensor which we don't need to go into right now. If canon ditches the 1.3x sensors, then that will be even more apparent. I am interested to see what the 1ds does this fall (not like I'm going to buy one though) as it should give some more indication of where they are going with the sensors

[lost]

I really feel that canon viex EF-S as a stopgap until FF sensors are economical to take over.

The reason I think this is because Canon is not producing L EF-S lenses.

I think at some point canon will stop developing EF-S lenses and Cameras. (The question is what point! I feel 4-5 years is a good time frame.

That said I would love to get a EF-S 600. Like you I cannot justify spending 4-7000 on a lens. About $2000 is my ceiling for and individual lens.

[Tom W]

A 600 f/4 EF-S lens would be nearly the same dimensions as the present EF 600 mm EF lens. Why? Because with telephoto lenses (and especially long ones), the large diameter of the lens is not a result of needing to project a larger image circle, but is instead needed to allow a larger aperture. A 600 mm f/4 lens needs a minimum entrance diameter lens element of 600/4 or 150 mm. Add a few mm of thickness for the housing and you have the 168 mm diameter that the 600 f/4 lens now has.

Any techniques that would shorten the physical length while maintaining a 600 mm optical focal length are available to full-frame as well as APS-C so there is no advantage there.

Where the EF-S lens is advantageous it's where short backfocus distance and decreased image circle are beneficial and that is at the wide-angle end of the focal-length spectrum. Decreased backfocus distance reduces the amount of optical correction needed on ultra-wide lenses where the distance from lens to sensor is longer than the optical focal length of the lens. As well, the decreased image circle reduces the lens diameter in cases where the f-stop doesn't dictate a larger lens. This, again, is true for wide angle lenses.

So, you probably won't see any telephoto lenses designed for EF-S, since there's no real advantage in terms of size and weight. At least not any reasonably long ones, anyway.

[Tom W]

Originally Posted by lost

I really feel that canon viex EF-S as a stopgap until FF sensors are economical to take over.

The reason I think this is because Canon is not producing L EF-S lenses.

I think at some point canon will stop developing EF-S lenses and Cameras. (The question is what point! I feel 4-5 years is a good time frame.

That said I would love to get a EF-S 600. Like you I cannot justify spending 4-7000 on a lens. About $2000 is my ceiling for and individual lens.

I don't see Canon stopping development on EF-S. The financial advantages of the smaller sensors are great, and users are generally very happy with the cameras that Canon and others are producing with APS-C sensors. The fact that they've developed a line of respectable EF-S lenses indicates to me that they intend to stay with the format for a good while.

That may not have been the original plan, but given the high sales of XT/20D/30D cameras, it would be hard for Canon to give up such a popular format.

[robert5_p]

Tom W wrote:

Originally Posted by Tom W

A 600 f/4 EF-S lens would be nearly the same dimensions as the present EF 600 mm EF lens. Why? Because with telephoto lenses (and especially long ones), the large diameter of the lens is not a result of needing to project a larger image circle, but is instead needed to allow a larger aperture. A 600 mm f/4 lens needs a minimum entrance diameter lens element of 600/4 or 150 mm. Add a few mm of thickness for the housing and you have the 168 mm diameter that the 600 f/4 lens now has.

If I understand your argument correctly, you are saying that the 1.6 crop factor applies to the image but, in particular, NOT to the large front elements of the 600 f/4. That is, the light entering the front lens elements is transformed in some significantly non-linear way onto the sensor.

To dispute your claim, I done the following experiment, which is easy to reproduce by anyone interested:
I took an old 58mm filter and cut a ring out of piece of paper with 58mm outer diameter and 36mm inner diameter (58/1.6 = 36) and then placed it against the old filter glass and on top of EF 70-300mm. Then I took bunch of pictures with my 1.6 x crop camera.
No vignetting at 70mm, at 150mm and at 300mm all pictures wide open!
My conclusion is that the front element on my EF 70-300 could have been made with 36mm thread instead of 58mm and much smaller other lens elements, if EF 70-300 was made into EF-S 70-300.
And I am concluding that I am not using significant portion of the outer diameter of the lens and that the light that passes through the outer part ends up outside of my smaller sensor.


Am I missing something?


Robert

[Tom W]

Originally Posted by robert5_p

Am I missing something?

Robert

Yes - the relationship of maximum aperture as expressed by the f/stop and focal length is a mathematical relationship. A 100 mm f/4 lens requires only a 25 mm input aperture. A 400 f/4 requires 100 mm. 600 f/4 needs 150 mm diameter. It's pure math. The focal length divided by the f/stop equals the minimum diameter of the entrance pupil diameter. A smaller entrance pupil will dictate either severe vignetting wide-open
or a smaller maximum aperture.

The geometry of the input side of the lens does not determine the image circle diameter on the output side. Follow the ray-tracing drawings of a lens and you'll see that the wide input capture is narrowed towards the nodal point of the lens, and then widens again to the approximate image circle that the lens is designed to project on the sensor/film plane. Also note that the variable aperture that allows you to stop down is located at or near the nodal point of the lens where the ray-trace is the narrowest.

[robert5_p]

Thanks Tom W,

I would love to argue, but that would be hard, especially since you are right and I was not.

I guess, I need to brush-up on my understanding of optics.
My new understanding is that each point on the senor/film ends up using the cone of light which spans the whole front lens element if the tele lens is wide open.

Well, my first post here made no sense whatsoever. The moderator may chose to delete it so it does not confuse anyone. Sorry.

Tom, thanks again for your patient explanation.

Robert

[Lightstream]

No, it's ok.. all of us are here to learn. I read the first post and got excited, but now I have a better understanding of the limitations involved - other replies served to teach me about other factors in lens design. Picking a lens is easy, designing a lens - now that's a whole different ball game.

However, I would hope that Canon's Diffractive Optics technology matures. You should see the 400 f/4 DO IS and how amazingly small it is compared to other big gun white primes. My local camera shop put one in the display window (presumably to tease people like me )

Perhaps we may yet get our small 600mm. The front element will still have to be huge and diffractive, but they would possibly be able to reduce the weight of other elements and shorten the barrel as they claim their DO technology allows them to do for the 400 f/4.

[GyRob]

i was guna say what Tom W said but that would have to be in another life as its way beond me
intresting thread and exsplaind well .
Thanks
Rob.

[lost]

Ok me thinks we all missed the boat on this one. What we are really talking about would be a 375 F4 which would give an effective 600mm lens. That would Definitely be much smaller than the 600L and lighter than the 400 DO.

I would go for that

Effectively the crop bodies allow for smaller lenses with the same "Effective" focal length.

[Matatazela]

My hope in all of this is that the sensor dimensions will stay the same as the 1.6 crop factor, but that minituarisation will allow better and better resolution. That is to say, a 10 - 12MP camera, with an EF-S sensor. That way, we get a 960mm equivalent in the space and weight of a 600mm with the resolution of a 5D!

[Matatazela]

Originally Posted by lost

Ok me thinks we all missed the boat on this one. What we are really talking about would be a 375 F4 which would give an effective 600mm lens. That would Definitely be much smaller than the 600L and lighter than the 400 DO.

I would go for that

Effectively the crop bodies allow for smaller lenses with the same "Effective" focal length.

Just get the Sigma 120-300mm f/2.8 and a 1.4X TC.

That takes us to 420mm f/4 and 672mm equivalent, when considering the 1,6 crop factor. Oh, I forgot... no IS!

[rklepper]

I think with the 17-55 Canon has shown that thier position is that an EF-S lens will not necessarily be any cheaper than its EF counterpart (or close to).

[Canuck]

Originally Posted by Matatazela

Just get the Sigma 120-300mm f/2.8 and a 1.4X TC.

That takes us to 420mm f/4 and 672mm equivalent, when considering the 1,6 crop factor. Oh, I forgot... no IS!

This is what I woulda said, verbatim. Sigma has OS, Optical Stabilisation, but the jury is out as to how it performs. Hmmm...OS on an already EX/APO/HSM/DG lens That would be a great idea if it is feasable and doesn't add another few thousand to the price. I'm impressed with the 672mm F4 effective lens. The only thing I forget sometimes is the 1/ focal length rule. I have jacked up many a pic that way.

Option B, 4/3s technology. Oly has a good idea there, but again, not dure if it took off like they hoped.