Why are Telephoto lens not so good?

Hi,

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I have seen many posts here saying, don't get a tele lens. That if you have the bellows draw, get a long lens as opposed to a telephoto lens. That tele lenses aren't as sharp or good as non-tele lenses of the same focal length.

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But why? In 35mm, the big glass of Canon and Nikon are the finest. According to tests they beat all other types of lenses. They are as good wide open as stopped down. I am refering to lenses like the 200/1.8, 300/2.8 and 600/4.

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In fact according to "photodo" the best lens they have ever tested is the Canon 200/1.8. And all the other big glass are pretty much runners up.

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So why is it in large format tele lenses are so down played?

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Thanks!

Regardless of the sharpness issue, a telephoto lens is

significantly larger and heavier, and have a much smaller image

circle. Compare for example a Fuji 450 with a Nikkor T 500.

The fact that the nodal point is way outside could also make

movements less intuitive.

Also, on 35mm cameras, there is considerable advantage to being able

to have a shorter barrel if there is a possibility that you might

want to hand-hold the camera or use it on a monopod. Older long

lenses for 35mm were not necessarily telephoto designs. The early

Canons came in two pieces and the 1000mm lens was really 1000mm long

(minus the 40mm or so from the flange to the film plane).

There are some positive aspects to telephoto lenses as well.

For a camera with limited bellows draw, a true telephoto lens

will allow it's use where another lens of equal photo length will

exceed the bellow draw capabilities of the camera.

Telephoto lenses for large format are larger, heavier, more

expensive and project a much smaller image circle than lenses

of more standard design and identical focal length, and they are

not as well corrected forfocusing distances closer than near

infinity. <P>

The telephoto lenses start to come into their own when you get

into the 500mm and longer focal lengths, but it doesn't make

much sense to get a 270 or 360mm telephoto when there are

several excellent 300mm lenses, like the NIkon 300mm �/9

M-Nikkor, availible at good prices.

Tele lenses for large format are "true telephoto" designs i.e. they

have a much shorter draw than their focal length indicates. This is

achieved by first creating an image and then enlarge this image by a

rear, negative lens group. It is similar to a true "Galilean

binocular", the first telescope ever invented. This enlargement of the

first picture "dilutes" and thereby makes less sharp the first image

created by the real image-forming lens group. The same thing is used

in astronomical observations and is called "Barlow lens", offering

larger magnification but lower resolution. The advantage: less draw

and higher magnification. The disadvantage: less performance.

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If you have the draw, my recommendation is to use a low-priced copy

lens of long focal lenght such as Apo Ronar or Claron. They have a

small aperture but are critically sharp at all scales down to 1:1

(provided you have THAT draw!).

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Regards

Staffan Johansson

Staffan,

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Your explaination makes sense. But still it does not explain why in

35mm telephoto lenses are the cream of the crop. Even more so when

you consider the small negative size. You would expect every flaw to

be magnified proportionally.

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One question about the G-Clarons and Apo-Ronars. These are the

classic "process" lens designs. They are optimized for 1:1. Then why

don't Schneider and Rodenstock call them Macro lenses? On the

contrary each has its own line of Macro lenses which are different

from the G-Clarons and Apo-Ronars!

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Thanks.

The fact that there are so many good telephoto lenses for 35mm cameras

should not come as a surprise. First of all, for the format to make

any sense, lightweight, compact lenses are a must. Otherwise, why

record an image on such a small area of film if you need to lug around

40 lbs. of equipment. Secondly, it is not nearly as challenging to

design and manufacture good performing telephotos as it is to build

good quality retrofocus lenses. The latter do kind of the opposite of

a telephoto, which is necessary for instant return mirrors to have room

to flip up and down in an SLR. These wide angles are the real

challenge!

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But, back to telephotos. One reason these lenses look good has a great

deal to do with the shallow depth of field one experiences when

shooting a distant subject with a long lens of any type. Because the

background is many times, out of focus by intent, the focused part of

the image appears very sharp by comparison to the blurred background.

Helping that along is the issue of scale. Because tele shots tend to

be comprised of simpler subject matter, with far less "information"

than you might encounter when shooting a vast expanse with a wide angle

lens, even slightly less than tack sharp elements take on an acceptable

appearance of sharpness. Any long lens is also much easier to focus

accurately for that reasen. If you were to make direct comparisons

between standard long focal length lenses and telephotos, no doubt you

could see a difference but, would you be willing to carry the extra

weight and a more stable tripod to be able to use them on small format

hand cameras? A friend of mine who is somewhat of a lens expert, has

built some adapters to allow the affixing of a 35mm Leica RF camera to

the back of his view camera. By use of a Visoflex viewing device, he

has been able to make some spectacular images with a host of Apo

Artars, Apo Raptars, Dagors, Commercial Extars and the like. Imagine a

24" Apo Artar on your Leica! Is this practical? I doubt it.

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But, addressing your original querry about why telephotos are not the

best way to go on a large format camera, my answer is: Like all

options, what makes sense for the type of work you do and the

techniques you use should dictate your decision. A tele may be just

fine for you. Consider the pros and cons. Telephotos have shorter

bellows draw requirements. They also have smaller image circles. When

you tilt or swing the lens, you will experience the odd effects of the

nodal point being out in front of the lens. If you want to do close up

work, you will have to apply an exit pupil factor once the image on

film exceeds 1/10th of the object's actual size. Is any of this going

to matter? If you shoot landscapes from great distances and have rear

tilt and swing on your camera, maybe not. I had a Fuji 300 T on my

Horseman 45FA and it worked very well. I've likewise heard very good

reports about the Nikons. I use a camera with longer bellows now and

so employ lenses that will work on my 8x10 as well. The graphic arts

lenses, BTW are wonderful at infinity. The Macro label associated with

some lenses may be more of a warning that these lenses won't cover the

intended format at infinity!

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That was probably more of an answer than you were looking for and I

apologize if I've repeated a number of other respondants comments, but

I hope it helps in some way.

Sol:

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I am not convinced that the best teles are worst than the best long

focus lenses any more. If you check out Chris Perez's tests, a Fuji

300T was nearly identical to 2 Nikkor 300Ms. Similarly, Nikkor 360

and 500 bracketed the performance of 2 Fuji 450Cs. MTF curves from

Schneider show the Apo-Tele-Xenar performing as well as the 300 Apo-

Ronar in the center of the field, with the Apo-Tele-Xenar having a

somewhat smaller image circle but more even performance to the

corners. So, everything said above about coverage, weight and

weirdness of nodal plane position is true, but pure optical

performance of some of these lenses is quite good. If you want

the "reach" of a long lens without the hassles of very long

extensions (wind etc.) they seem like a perfectly reasonable choice

if you can live with their limitations. I suspect a lot of the

reputation is due to older design teles from the 50's and 60's

designed for press work.

Glen,

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Thanks for your post. One of the reasons I posted this question was

because from my own experience I found the contrary. One of my best

performing lens is a telephoto. It is the new Apo Tele Xenar Compact

400mm from Schneider. It is awesome even when used wide open at f5.6.

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So I don't know why they are regarded as being inferior.

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Thanks.

Sol... I was very skeptical about teles for a long time...however,

when I wanted to go very long, 800 and 1200mm, I had no choice, so I

bought the Nikors. The image circle is just large enough to cover

8x10...I was not setting my expectations very high considering I

would be comparing these results with some of the sharpest LF lenses

such as SS XL's and Fuji A's etc. After getting my first chromes

back, I wasu truly blown away at the resolution and contrast these

teles produced! Now I am a big tele fan...of course in shorter fl's

I would find their shortcomings to much to deal with as I do like to

use movements and appreciate the large image circle offered by non

tele lenses.

Bill,

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I presume you have the 800 and just the rear element for the 1200.

How do they work out? Is wind a problem? Is the 1200 as sharp as the

800? What is it like focusing at f18?

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Tell us more about these monsters!

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Thanks!

I know of a photographer who shoots sea lions with his 1200 Nikkor. Amazing isn't it! Hey Bill?

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Sol, having the image of a 400 at 5,6 on the GG must be a real pleasure! In low light, it's a pain to focus even at f9.0.

Have you noticed any effects of the shake at some shutter's speeds with your Copal#3 New Tele-Xenar or is this

shake issue a none-sense? I think you use it on a folding camera?

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I would suggest one more thing to consider when choosing a tele over a long lens: it's the camera stabillity at long

extension. A long lens might be sharp, but due to stabillity factors, a tele might give better results on some cameras,

when the heavy weight would suggest otherwise. On other cameras, a light lens even at full extention will be hold

still enough to produce sharp shots. Strong tripod is also very important. There is an alchemy in all the elements!

Sol, their is only one front element for the 600, 800 and 1200

mm. You buy any of the rear elements which is a small barrell say

1.5" in diameter and 2" long. They each contain a thin piece of

magnifying glass in them. It's hard to fathem when looking at the

rear elements just how expensive they are?

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The worst part of these lenses is their size! Forget

backpacking with this puppies unless you have lamas with you. The

weight can be a problem also if your camera is not sturdy enough.

However, my Toyo 810MII and my Toyo VX125 with 1000mm of rails is

very stiff. With 4x5, I do use two tripods, it is very solid...with

8x10 I put a monopod under the front standard on windy days,

otherwise the 8x10 is OK with one tripod, but a good strong one! I

use the Gitzo Carbon fiber 1349.

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As for which is sharper? Well I have had better luck with

the 1200mm, but it's probably just because I used it more often. So

I would imagine they are very close to the same in quality. As for

focusing at f18...considering I only shoot them in daylight and have

a very well made hooded dark cloth with elastic band for both

cameras, it's not as bad as I thought. I am not sure if the tele

design which allows for almost half the extension as their non tele

cousins, actually seem to dump more light on the gg? Does anyone

know if this shorter extension reduces light loss vs. the longer

extension required on non teles? From looking in the gg, I would

think I saved a stop?

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The one thing which is really amazing is just how tiny the

DOF really is! WOW...you better shoot everything at infinity, unless

you can accept a very blurred background.... Yes, Paul was right, I

have shot sea lions with the 1200 on 4x5 with fair results, you have

to catch them really still since the shutter speeds are very long,

like 1/4 second at the fastest, but quite often 1/2 to 1 second. But

soon I plan to try Provia 400F and see if I can pick up 2 or 3 stops

of speed. That would really help these lenses out!!

I think there's some confusion in your original question and in some

of the responses based on incorrect usage of the term "telephoto"

lens. There is no such thing, to my knowledge, as a telephoto lens in

35 mm format. Based on your reference to Nikon and Canon 35 mm lenses

of 200 and 300 mm focal lengths, I think you are using the

term "telephoto" to simply mean a long focal length lens. This is a

very common mistake. Used in this incorrect way (i.e. to mean a lens

with a long focal length) I don't think anyone would suggest that

long focal length lenses for large format cameras are inherently

inferior to shorter focal length lenses. In fact there are some

outstanding lenses in the range of 300 mm and up for large format

cameras.

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The disparaging remarks about "telephoto" lenses to which you refer

were using the term "telephoto" in its true meaning. A "telephoto"

lens isn't simply a lens of a long focal length but instead refers to

a particular lens design in which the image nodal plane is placed in

front of the lens rather than within the body of the lens. Thus a

telephoto lens has a shorter lens to film distance than a normal lens

of the same focal length and allows large format cameras with

relatively short bellows lengths to be used with relatively long

focal length lenses.

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The criticisms of telephoto lenses (using the term in its correct

meaning) are largely based on older telephoto lenses, which tended to

produce negatives with lower contrast and possibly somewhat less

resolution than normal design lenses of the same focal length. This

has changed a lot with modern telephoto lenses and I doubt that you

would notice any difference between a negative made with a normal

design lens and a negative made with a modern telephoto lens unless

you made a very careful comparison and even then I think the

difference would be pretty minimal. I used the Fuji 400T telephoto

lens for many years and it was outstanding.

Brian,

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Sorry to have to correct you Brian, but almost all lens marked

with a long focal length for 35mm cameras are true telephoto

designs, especially once you get get longer than the 105 to

135mm range of focal lengths.

Brian: Have to agree with Ellis here... as an example, a Canon 400mm

f/5.6 lens is only 256mm long, so unless Canon bodies swell to 150mm

thick (6 inches) it's got to be a true telephoto! Other longer lenses

follow suite, for example, the 300mm f/4L is only 213mm long, and

those lengths go from the front of the filter thread to the back of

the lens mount. Even the 200mm f/2.8 is only 136mm long.

Well, you learn something new every day. I dind't realize that

(obviously). Thanks for the correction and sorry for the

misinformaion.

Brian: No problem... we all learn something new everyday on this

forum... that's why we visit it.