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LENSES: Facts and Fallacies - Part XI
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PostPosted: Sat Apr 19, 2014 3:34 pm    Post subject: LENSES: Facts and Fallacies - Part XI Reply with quote

Thirty or forty years ago, zoom lenses were viewed with suspicion by many photographers, especially the professionals. Zoom lenses were large, heavy, expensive, and the image quality was not as good as that of prime lenses. Over time zoom lenses were being improved, and today the best zooms produce image as good as the primes. In particular, zooms like 24-70mm F2.8 and 70-200mm F2.8 became the workhorse of today's professionals. The Nikkor 14-24mm F2.8 virtually wiped out the ultra wide-angle primes. Even fisheye zooms, such as the Canon 8-15mm F4, have been successfully designed.

Despite all the progress in the design of zoom lenses, they still have some disadvantages compared to primes. For example, the Canon 80-200mm F2.8 is much heavier and larger than any prime with focal length between 80 and 200mm. Also, there is virtually no zoom lens for FF with aperture F1.4, F1.5 or F1.8, whereas normal lenses with large apertures have existed since the beginning of XX century. For example, the Ermanox camera was already announced in 1924 camera with a Bertele's Ernostar F1.8 lens.






to be continued...


Last edited by Gerald on Sun Mar 05, 2017 5:48 pm; edited 1 time in total


PostPosted: Sat Apr 19, 2014 4:29 pm    Post subject: Re: LENSES: Facts and Fallacies - Part XI Reply with quote

Gerald wrote:
Despite all the progress in the design of zoom lenses, they still have some disadvantages compared to primes.


And some advantages - you can change framing/magnification without changing perspective.

Quote:
For example, the Canon 80-200mm F2.8 is much heavier and larger than any prime with focal length between 80 and 200mm.


And how much heavier is it than 3 primes at, for example, 85, 135 and 200 mm ?

For the record, the Canon 200 mm, f/2 is twice the weight of the zoom - although it is of course faster.


PostPosted: Sat Apr 19, 2014 6:28 pm    Post subject: Re: LENSES: Facts and Fallacies - Part XI Reply with quote

Gerald wrote:
... today the best zooms produce image as good as the primes. ...


Nonsense.


PostPosted: Sat Apr 19, 2014 9:10 pm    Post subject: Re: LENSES: Facts and Fallacies - Part XI Reply with quote

visualopsins wrote:
Gerald wrote:
... today the best zooms produce image as good as the primes. ...


Nonsense.



You can read a MTF chart? Rolling Eyes

So please go to the Canon website, read the MTF charts, come back, and prove to us all that the prime 200mm F2.8 produces a better image than the zoom 70-200mm F2.8. I doubt you can...


PostPosted: Sun Apr 20, 2014 12:14 am    Post subject: Re: LENSES: Facts and Fallacies - Part XI Reply with quote

Gerald wrote:
visualopsins wrote:
Gerald wrote:
... today the best zooms produce image as good as the primes. ...


Nonsense.



You can read a MTF chart? Rolling Eyes

So please go to the Canon website, read the MTF charts, come back, and prove to us all that the prime 200mm F2.8 produces a better image than the zoom 70-200mm F2.8. I doubt you can...


Canon 70-210/2.8:


Canon 200/2.8:


Canon 200/2:


PostPosted: Sun Apr 20, 2014 1:57 pm    Post subject: Re: LENSES: Facts and Fallacies - Part XI Reply with quote

visualopsins wrote:
Gerald wrote:
visualopsins wrote:
Gerald wrote:
... today the best zooms produce image as good as the primes. ...


Nonsense.



You can read a MTF chart? Rolling Eyes

So please go to the Canon website, read the MTF charts, come back, and prove to us all that the prime 200mm F2.8 produces a better image than the zoom 70-200mm F2.8. I doubt you can...


Canon 70-210/2.8:


Canon 200/2.8:


Canon 200/2:


No comment? So you proved nothing, except that you can copy an MTF chart. Laughing

First, you should ignore the Canon 200mm F2 because there is no commercial zoom lens with this focal length and aperture. Let's not compare apples with oranges, OK?

Second, you picked the older Canon 70-200mm F2.8. You should have picked the newest Canon 70-200mm F2.8, which has better performance. Here is its MTF for 200mm:



Pay attention to the continuous and dashed thin black lines, which give the wide open sagittal and meridional MTF for 30 lines/mm as a function of the distance to center. The MTF for 30 l/mm are important because it tells how a lens reproduces fine details. In other words, the higher the MTF the more sharp is the lens.

Note that the MTF for the prime 200mm F2.8 is only 0.6 for most of the field. In contrast, the MTF for the zoom starts from 0.9 in the center but the sagittal component stays above 0.8 for most of the field. The medional component is above 0.7 within a circle with diameter of 20mm, and only drops to 0.6 or less in the extreme corners.

Conclusion: The zoom 70-200mm F2.8 is sharper than the prime 200mm F2.8. Repeating what I said before "today the best zooms produce image as good as the primes".


PostPosted: Sun Apr 20, 2014 2:57 pm    Post subject: Reply with quote

Gerald, about apples and oranges. What apertures are the MTF curves you posted for? What are they like at typical shooting apertures?


PostPosted: Sun Apr 20, 2014 3:07 pm    Post subject: Reply with quote

danfromm wrote:
Gerald, about apples and oranges. What apertures are the MTF curves you posted for? What are they like at typical shooting apertures?


Wide open and F8. Typical? I think so. Further information:

http://www.learn.usa.canon.com/resources/articles/2013/reading_MTF_charts.shtml


PostPosted: Sun Apr 20, 2014 4:57 pm    Post subject: Re: LENSES: Facts and Fallacies - Part XI Reply with quote

Gerald wrote:
Gerald wrote:
visualopsins wrote:
Gerald wrote:
... today the best zooms produce image as good as the primes. ...


Nonsense.


You can read a MTF chart? Rolling Eyes


No comment? So you proved nothing, except that you can copy an MTF chart. Laughing


Your self importance is too much for me...


PostPosted: Sun Apr 20, 2014 5:01 pm    Post subject: Reply with quote

Only best zooms reach level of better primes, I did try hundred of lenses by myself, author article was paid for to sell lenses. Always better to try lenses than read article look MTF charts, buy , try and sell if you not like it , best way.


PostPosted: Sun Apr 20, 2014 5:14 pm    Post subject: Re: LENSES: Facts and Fallacies - Part XI Reply with quote

visualopsins wrote:
Gerald wrote:
Gerald wrote:
visualopsins wrote:
Gerald wrote:
... today the best zooms produce image as good as the primes. ...


Nonsense.


You can read a MTF chart? Rolling Eyes


No comment? So you proved nothing, except that you can copy an MTF chart. Laughing


Your self importance is too much for me...


We are discussing lenses! Shocked Do not shoot the messenger!!! Smile
What are your technical arguments? Please give me one, just one good technical argument. Idea


PostPosted: Sun Apr 20, 2014 5:53 pm    Post subject: Reply with quote

Attila wrote:
Only best zooms reach level of better primes, I did try hundred of lenses by myself, author article was paid for to sell lenses. Always better to try lenses than read article look MTF charts, buy , try and sell if you not like it , best way.


Exactly!
MTFs tells nothing about CA, distortions and just partially about the general character of a lens. And the lens "character" is what most people on this forum consider important to a lens, that's what makes some lenses better than others.
As long as we don't define what is "a good image" your statement "... today the best zooms produce image as good as the primes. ..." is ambiguous and has yet to be proven.
I'd say that "a lens with a strong character produces a better image than one with a weak one"

Resolution and contrast are important in defining the character of a lens but don't make by themselves some lenses better then others. Otherwise why we'd still bother with old MF lenses and not use exclusively the latest AF Japanese zooms?


Last edited by dan_ on Sun Apr 20, 2014 6:11 pm; edited 2 times in total


PostPosted: Sun Apr 20, 2014 6:05 pm    Post subject: Reply with quote

dan_ wrote:
Attila wrote:
Only best zooms reach level of better primes, I did try hundred of lenses by myself, author article was paid for to sell lenses. Always better to try lenses than read article look MTF charts, buy , try and sell if you not like it , best way.


Exactly!
MTFs tells nothing about CA, distortions and just partially about the general character of a lens. And the lens "character" is what most people on this forum consider important to a lens, that's what makes some lenses better than others.
And in this regard your statement "... today the best zooms produce image as good as the primes. ..." has yet to be proven.

Resolution and contrast are important in defining the character of a lens but don't make by themselves some lenses better then others. Otherwise why we'd still bother with old MF lenses and not use exclusively the latest AF Japanese zooms?


Very true! Very Happy


PostPosted: Sun Apr 20, 2014 6:10 pm    Post subject: Reply with quote

dan_ wrote:

MTFs tells nothing about CA, distortions and just partially about the general character of a lens.


The MTF tells a lot about a lens. Including CA!
The figure below from a Zeiss article comments how the lateral CA affects the tangential (meridional) MTF:



Figure extracted from:
http://lavidaleica.com/assets/reviews/zms/en_CLN41_Nasse_LensNames_Distagon.pdf


PostPosted: Sun Apr 20, 2014 6:21 pm    Post subject: Reply with quote

[edited

Last edited by bernhardas on Tue May 17, 2016 7:18 am; edited 1 time in total


PostPosted: Sun Apr 20, 2014 6:32 pm    Post subject: Reply with quote

Gerald wrote:

The MTF tells a lot about a lens. Including CA!
The figure below from a Zeiss article comments how the lateral CA affects the tangential (meridional) MTF:


It tells that lateral CA affects the tangential MTF. So it only tells that CA affects MTF. As other factors could affect the tangential MTF as well it doesn't speak about CA.
The cause -> effect link is CA -> MTF (as I can read in last rows of your MTF example).
The revers is not always true. You can't always draw a conclusion about CA by reading the MTF.


PostPosted: Sun Apr 20, 2014 7:03 pm    Post subject: Reply with quote

dan_ wrote:
Gerald wrote:

The MTF tells a lot about a lens. Including CA!
The figure below from a Zeiss article comments how the lateral CA affects the tangential (meridional) MTF:


It tells that lateral CA affects the tangential MTF. So it only tells that CA affects MTF. As other factors could affect the tangential MTF as well it doesn't speak about CA.
The cause -> effect link is CA -> MTF (as I can read in last rows of your MTF example).
The revers is not always true. You can't always draw a conclusion about CA by reading the MTF.


Yes, astigmatism also produces separation of the sagittal and meridional curves. However, it is possible to distinguish whether the separation is produced by lateral CA or astigmatism.

If the meridional MTF curve practically does not change with aperture then the predominant off-axis aberration is lateral CA. This is the case of the Canon 300mm F4:
http://www.usa.canon.com/cusa/consumer/products/cameras/ef_lens_lineup/ef_300mm_f_4l_is_usm

Note that out of the central zone, the black and blue dashed lines are very close one from the other.


PostPosted: Sun Apr 20, 2014 9:49 pm    Post subject: Reply with quote

"Prime lenses give sharper images. This is because zoom lenses have much more glass for the light to travel through in order to reach the sensor; extra elements are required to zoom in and out, and even more are needed to correct the aberrations created by all the extra elements. With the light altered so many times, it is bound to degrade. A prime lens, on the other hand, preserves the integrity of the image by its simple design. Having only one focal length and fewer moving parts, it can be much more precisely calibrated for maximum sharpness."


PostPosted: Sun Apr 20, 2014 10:31 pm    Post subject: Reply with quote

Gerald wrote:

If the meridional MTF curve practically does not change with aperture then the predominant off-axis aberration is lateral CA. This is the case of the Canon 300mm F4:...

That's correct, in some particular cases some conclusions can be drawn, as in your example. But not in all cases. My assumption remains valid : "You can't always draw a conclusion about CA by reading the MTF."

In fact that was not my point. My point was that your statement "... today the best zooms produce image as good as the primes. ..." is not valid simply because a "good image" can't be defined in such a manner that everybody will accept it. A good image is a image good for something - landscape, portrait, close up etc. There is not such a thing as a generic "good image".
A lens is only a tool and a specialized tool (mostly a prime) is, in most cases, a better tool than a generic one (mostly a zoom) in producing an image good for something .


Last edited by dan_ on Sun Apr 20, 2014 11:06 pm; edited 2 times in total


PostPosted: Sun Apr 20, 2014 10:35 pm    Post subject: Reply with quote

And Gerald, as an example the Canon EF 70-200mm f/2.8L IS II USM has just a messured transmission of 3.4T, while the Canon EF 200mm f/2.8L II USM has a transmission of 3.1T. Theoretical numbers are the same (f/2.8 ) but messured light transmission is much better thru a prime lens.


PostPosted: Sun Apr 20, 2014 10:41 pm    Post subject: Reply with quote

Quote:
From what has been said, it is clear that neither resolution, sharpness,graininess, nor tone reproduction is of itself the determining factor for good definition in a photograph. In order to combine these properties in the simplest way, it has recently become customary to express the performance of a lens by its modulation transfer function (MTF), on axis and at several points in the field.

As its name implies, MTF is a measure of the ability of the lens to form an image that is an accurate reproduction of an object


I grabbed this quote from Rudolf Kingslakes book "Optics in Photography". I added the bold.

If MTF is just about showing how a lens reproduces an image by expressing it in a chart format, that can be easily read and understood by lens technicians to help them on how a lens will perform, or if it is worth while going ahead with a lens design...it is only a small drop in the bucket as to why we use a lens. I believe we enjoy seeing the result of a particular lens regardless of what the MTF charts say,there are so many factors an MTF chart can not cover.

This is a discussion that can get lost in mind numbingly small details....although the discussion can be interesting.


PostPosted: Sun Apr 20, 2014 11:41 pm    Post subject: Reply with quote

Nordentro wrote:
"Prime lenses give sharper images. This is because zoom lenses have much more glass for the light to travel through in order to reach the sensor; extra elements are required to zoom in and out, and even more are needed to correct the aberrations created by all the extra elements. With the light altered so many times, it is bound to degrade. A prime lens, on the other hand, preserves the integrity of the image by its simple design. Having only one focal length and fewer moving parts, it can be much more precisely calibrated for maximum sharpness."


Where did you get this from? And why should I believe it? It seems like the veriest nonsense.

Oh, and by the way, I have a few zooms of varying degrees of complexity and a few primes as well. My long Schneider zooms for my Beaulieus are marvels but within its range the 8.5-26.5/1.0 that's permanently attached to my Canon 310XL gives better footage. Good primes, e.g., 25/1.4 Cine Ektar II and 100/2 Canon TV-16, give better still.

But all this misses the point of zooms. Some of us have them because we're stuck with them. Get a 310XL, have a fast zoom, end of that discussion. Others choose to get zooms, e.g., my humble 35-70/3.5-4.5 Nikkor, because they fill a need. Ultimate sharpness isn't part of the need even though by MP's test my little piece of plastic is a decent lens.

I doiubt that many people buy lenses because they're best by some test or other. Seems silly.

dan_, I'll all for solidarity among Dans but please, sir, understand clearly that you don't speak for me. Its fine with me that there are many posts here about how various lenses render but rendition isn't very important to me. To the posters, yes, and I don't want them to stop caring about what's important to them, but to me, sorry, no.


PostPosted: Sun Apr 20, 2014 11:52 pm    Post subject: Reply with quote

danfromm wrote:

dan_, I'll all for solidarity among Dans ...

Very Happy


PostPosted: Mon Apr 21, 2014 12:27 am    Post subject: Reply with quote

From here:

http://www.picturecorrect.com/tips/5-reasons-why-prime-lenses-are-better-than-zoom-lenses/

It makes sence to me! The video with Kai is very entertaining too Very Happy

But seriously, those who knows me know that I don`t care about MTF charts and I have never bought a lens because of one either Wink
If if feel the need of a zoom for an occasion, I use a zoom too!

My point (in this discussion) was just, primes have better IQ in general because they have a few benefits but it doesn`t mean that you should avoid zooms or that there isn`t any good zooms. Wink


PostPosted: Mon Apr 21, 2014 3:17 am    Post subject: Reply with quote

Visualopsins and Nordentro are correct.

Here is why we use MTF today to judge lens quality instead of lp/mm: zoom lens makers realized that lp/mm ratings show that zoom lenses perform poorly. However, they can be made to have a modular transfer function that's kinda almost like an average prime. My FA Limited lenses test out at around 162-165 lp/mm at their best aperture. Even the old kit Pentax 50mm f2 tested out at around 160 lp/mm. The BEST Canon L series zoom at its best aperture comes in around 120 lp/mm.

For edification, do a quick Google search for lp/mm ratings on major maker zoom lenses. You either won't find them or it will be hard. Camera makers do what they can to keep lp/mm data quiet and the long-term anti-lp/mm campaign has been so successful that people now believe that MTF is actually a measure of lens quality.

For the record, if I remember correctly, at least one of those two is or used to be an optics engineer (correct me if I'm wrong.)