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08-16-2009, 11:12 PM   #1
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Why do people love super telephoto primes?

Hi, just wondering why a great number of people are content with lenses such as a 300mm fixed focal length lens. At that range, wouldn't people much rather have somewhat of a range?

I guess if you're trying to shoot really far and you want to be able to crop... that's cool or for macro stuff (is that the main reason)???

Just beware that if it's for some crazy reason, i may have to end up buying one

08-16-2009, 11:46 PM   #2
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Just a guess - but maybe price and IQ? The long lenses are harder to make than, say, a normal lens, so if you make a zoom (that's what you mean by range, right?), it's gonna be even more expensive; good build quality and image quality will be even of more expense.

QuoteQuote:
I guess if you're trying to shoot really far and you want to be able to crop... that's cool or for macro stuff (is that the main reason)???
Nope... What you're saying is, imho, much better done with close-focusing wide angles (that is, if you're willing to crop for a "macro" shot). They have a wider depth of field, and shake is much less evident. Usually, macro lenses are in 100mm range - long enough to not be too close to the subject, and not too long for shake to be prohibitive. Try focusing with a 200mm at something a meter away (I tried that once with a couple of extension tubes) and you'll realize you really need a tripod for that.

Last edited by pbo; 08-16-2009 at 11:52 PM.
08-17-2009, 12:03 AM   #3
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In general, IQ of zooms lenses is not as great as that of primes. Also, for most zoom lenses, the IQ is at its worst at the greatest focal length.

Zoom lenses are normally longer and heavier than primes. Handling a zoom lens thus requires more effort and steadier hands and arms.

Zoom lenses, especially ones of great focal length, are slower than primes. Slower lenses require slower shutter speed, a big disadvantage with lens of great focal length.

All these combines make primes much more desirable. Also, there is a very good chance that you need to crop. Every single bit of IQ helps.

I don't think "macro" is a reason. Great focal length requires steady hands and arms. Macro requires steady hands and arms. Both of them combine means big stable tripod.
08-17-2009, 06:01 AM   #4
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QuoteOriginally posted by esman7 Quote
Hi, just wondering why a great number of people are content with lenses such as a 300mm fixed focal length lens. At that range, wouldn't people much rather have somewhat of a range?

I guess if you're trying to shoot really far and you want to be able to crop... that's cool or for macro stuff (is that the main reason)???

Just beware that if it's for some crazy reason, i may have to end up buying one
I quickly found that for birds, I was almost always speed and distance limited. Not only would I have to crop, but the low f-number of zooms at the long end made stability & focus difficult.

Do high quality 300mm constant f4 zooms even exist?

08-17-2009, 06:31 AM   #5
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Size and weight. Super telephoto lenses are big, super zooms are huge.
As an example, my A*600/5.6 is 133 x 386 mm and weights 3.280 kg, the FA 250-600/5.6
is 134 x 442 mm and weighs in at 5.400 kg.
Granted the zoom offers AF, but the length and weight penalties are tremendous.
08-17-2009, 07:42 AM   #6
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Ok that makes a lot of sense - I hadn't taken the size aspect of the lenses into account.

Thanks for your replies!
08-19-2009, 01:41 PM   #7
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QuoteOriginally posted by esman7 Quote
Hi, just wondering why a great number of people are content with lenses such as a 300mm fixed focal length lens. At that range, wouldn't people much rather have somewhat of a range?

I guess if you're trying to shoot really far and you want to be able to crop... that's cool or for macro stuff (is that the main reason)???

Just beware that if it's for some crazy reason, i may have to end up buying one
The longer the focal length becomes, the more expensive the lens gets, IF you want a decently fast lens. A prime lens of 300mm fl with a max, aperture of 4.0 is still affordable. A zoom with max. aperture is very rare (the Sigma 100-300/4 is the obvious contender) and more expensive. Also, if you consider really long lenses, like 500mm, zooms get really slow ( The Bigma is 1:6.3 at 500mm), wheras you can buy an old Pentax 500/4.5 for just a bit more than half the cost of the Sigma.

So price and a fast max. aperture are two points in favour of primes. Another one is the application of such long lenses. In most situations, where you need to use a long lens (wildlife, birds etc.) you end up using the longest fl of a zoom anyway (that's my personal experience and I know quite a few people, who have made the same experience). So, why then use a zoom with all the associated compromises?

Ofcourse there are situations, where a zoom is more convenient or may give you a shot, which you may have missed with a prime. But that really depends on your subjects and your personal approach.

Ben
08-20-2009, 07:21 AM   #8
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also the longer the focal length becomes, the less percieved difference there is in its application

50mm and 100mm offer completly different fields of view

600mm and lets say 550mm or 650mm, you would be hard pressed to notice any real diffence.

so at that range implementing a zoom function is not as utilitarian

remember that to get twice the magnification you need to double the focal length

so if you are using a 50mm, to double you would use 100mm, to double that you would need 200mm, then 400mm then 800mm, then 1600... so the higher you go, the less impact individual MM's actual make.

on the other side, super-wide angle lenses benefit from every mm you can squeeze out, which is why the 16-55 range lens is a "kit", as it covers the majority of things people would bother shooting.

08-20-2009, 08:06 AM   #9
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One thing that you can have, of course, is an older 75-300 or 100-300 lens: or something less ambitious in the 80-200 sort of range... some of the older ones are pretty fast, (compared to what's out there, these days: the trend for these went toward smaller, slower, and variable aperture,even before digital. Also the longer ones will tend to be variable aperture and/or slower) and they have some good reach on a cropped sensor. There's a gazillion of them out there, cause it was what every parent of a young budding sports star had to have. They pretty much come in all shapes and sizes and qualities. A little harder to find a faster one with the A compatibility, (No Kirons, *sniff.* ) But there's plenty out there.

The sharpness and image quality won't be as good as with a prime, but you can have some fun with them. I had a pretty nice 100-300 5.6 for my old Canons, ages ago: sold it when I stopped doing any sports and such, but it'd probably be neat on a cropped sensor. (The zoomage was actually fairly useful for scholastic and amateur sports, cause you could get right down on the sidelines, and a lot of the best shots would happen when the action got closer. )

It's not an area where I foreseeably need to worry about top quality, so I'll probably have some fun with cheap telephoto, when I get around to it, myself. Especially if we end up living somewhere with a view.
08-20-2009, 09:08 AM   #10
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QuoteOriginally posted by newarts Quote
Do high quality 300mm constant f4 zooms even exist?
The lenses that come to mind are the Sigma 100-300/4 and even more so the Nikkor 200-400/4. Needless to say that last one is quite expensive, but also unique and if it suits you would be a pretty good reason to be shooting Nikon. Tests on the Sigma also show it doesn't give up too much quality compared to 300/4 primes.
08-20-2009, 09:47 AM   #11
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A 28-300 is slow and unimpressive IQ, at the long end.

Often when using extremely telephoto lenses, you need all the reach you can get. So with a zoom, you would likely most be at the long end.

On his higher MP cams, Michael Reichmann is not particularly happy with his Canon 100-400 f/5.6L IS.

The bazooka zoom Pentax 250-600 is a very rare combination.

The sigma 200-500mm F2.8, is a 15,7 kg lens !

Canon has the DO design, which brings the weight down on ultra tele lenses. But they come at an extra price penalty
08-20-2009, 04:50 PM   #12
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Primes generally are a higher quality...I don't know the science of it. From what I hear, they are easier to make faster, too....don't know the science of that either.

Anyway, you have a faster, better quality lens. I REALLY would love to have a DA* 200 2.8 (I would like to see it in a 2.0 but eh)
08-25-2009, 01:55 PM   #13
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QuoteOriginally posted by MJB DIGITAL Quote
Primes generally are a higher quality...I don't know the science of it. From what I hear, they are easier to make faster, too....don't know the science of that either.

Anyway, you have a faster, better quality lens. I REALLY would love to have a DA* 200 2.8 (I would like to see it in a 2.0 but eh)
Yeah, I guess that's the start of a new thread... "Why do primes give better IQ?"
08-25-2009, 03:42 PM   #14
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QuoteOriginally posted by esman7 Quote
Yeah, I guess that's the start of a new thread... "Why do primes give better IQ?"
Why are primes better than zooms? Good question and I’ll give it a shot. I think it is because a zoom lens is all about compromises through its entire focal range. In order to keep down size, price and still make a good optic a lot of compromises have to be made.

Older zooms of 20-30 years ago were pretty sad when compared to their prime counterparts in terms of IQ. This is still the case with many cheap zooms of today although they have come a long way. Premium zooms such as The Pentax DA* series and Canon L series certainly approach the IQ of a prime lens. I haven’t done a study but I suspect a quality 300mm prime will still outperform a zoom at that particular focal length because it is optimized to do so.

I’m sure Wheatfield and Ben Edict will have some thoughts on this one. Am I out to lunch on this one guys or do telephoto primes still rule?

Last edited by 8540tomg; 08-25-2009 at 03:50 PM. Reason: typo
08-26-2009, 01:45 AM   #15
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QuoteOriginally posted by 8540tomg Quote
Why are primes better than zooms? Good question and Iíll give it a shot. I think it is because a zoom lens is all about compromises through its entire focal range. In order to keep down size, price and still make a good optic a lot of compromises have to be made.

Older zooms of 20-30 years ago were pretty sad when compared to their prime counterparts in terms of IQ. This is still the case with many cheap zooms of today although they have come a long way. Premium zooms such as The Pentax DA* series and Canon L series certainly approach the IQ of a prime lens. I havenít done a study but I suspect a quality 300mm prime will still outperform a zoom at that particular focal length because it is optimized to do so.

Iím sure Wheatfield and Ben Edict will have some thoughts on this one. Am I out to lunch on this one guys or do telephoto primes still rule?
You pretty much summed the reasons up! From a technical perspective it is also quite easy to understand, why a zoom usually is not as good as a quality prime (we shouldn't forget, that there are also very poor prime lenses...):

Basically a zoom lens consists of a primary lens with a fixed focal length. After that we have a lens group which is called the "variator". This varietor group is in principal a sliding teleconverter. The distance between this varietor and the the other lens elements and especially between the variator and the sensor/film plane determines the magnification. As the variator slides front to back and vice versa, the magnification varies.
After the varietor there are usually some correcting elements, because the variator has limitations: the higher the magnification gets, the smaller the field of view will be, introducing vignetting. This needs correction. Also the shifing of the focal length would lead to a shift of the focal plane, which we do not want. Therefore there is some kind of projection element (a relay group) at the rear of a zoom lens, which makes the fixed focal plane possible. And ofcourse more lens elements also may introduce more residual colour abberrations. Also, we shouldn't forget, that a teleconverter (aka the variator) works best at a certain distance to the primary lens and to the focal plane. Any other position will lead to increasing loss of contrast and sharpness at the corners. The farther away the tc is from its optimum position, the smaller the useable center of the image circle will be.

Modern zoom lenses are more complicated, especially if they introduce internal focusing etc., but the basics are enough to understand , why zooms usually have lower IQ. Also the travel of the variator must not neccessarily been a mechanical travel, but can be achieved by moving different elements against each other, such achieving the "travel" by projection variations:

1. the primary lens group has a fixed fl, usually about the shortest fl, the zoom lens delivers
2. the variator magnifies the image of that primare lens group
3. in doing so, all abberrations and other shortcomings of the primary group will be magnified, too (just like using a tc)
4. the variator group introduces loads of problems, as it works far out of its optimum distance from lenses and focal plane.

This explains easily, why "super-zooms" (18-200 etc.) have such limited quality: the primary lens group has a comparetively short fl and the variator needs to travel through a large distance, with a large degree of magnification variation. A short fl for the primary lens means, more distortions and higher amount of spherical abberration (mostly corrected by using aspherical elements somewhere in the optical train), which will be highly magnified by the variator. Also the varietor has to travel far more with a short primare lens, to achieve a resulting long fl, so that it works very far from its optimum position - this explains the usually break-down of performance at the longest setting.

Ben
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