prime vs zoom when stopped down..

In theory, the light path through the primes will be simpler than that through the zoom.

Don't forget that the lenses are wide open for focussing, whether you use AF or MF, so the extra light the fast primes let through helps a lot.
 
blinkerz said:
Is there any advantage to using primes such as 85L 1.2 / 135 2.0 L instead of the 70-200 2.8 IS when shooting around f8-f11.
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I was shooting in a studio using my 85f1.2 there was not a lot of room so I put on a 24-70L and the shots from the zoom at f11 were every bit as good as the 85f1.2 so I sold it for that reason.
 
blinkerz said:
Is there any advantage to using primes such as 85L 1.2 / 135 2.0 L instead of the 70-200 2.8 IS when shooting around f8-f11.
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In a word, no. The only real advantage of primes is at low f/numbers and anyway, at high f/numbers, diffraction will be the limiting factor on sharpness.

The reality of diffraction hits crop format DSLRs from about f/5.6, and full frame from f/8 or so.

See if you can split these two - 135L vs new 70-200L 2.8 MkII. I can't. http://www.the-digital-picture.com/...meraComp=453&SampleComp=1&FLIComp=2&APIComp=4 That new zoom is just incredibly sharp, but of course it is much heavier, and twice the price. And it doesn't do f/2 very well...

Load up any combination of lens, focal length and f/number on that site, including with a telecon. Toggle between the two on the little central arrow.
 
Primes are designed for one angle of view whereas zooms obviously aren't although I suppose that a zoom could be designed to be at it's very best at a particular angle of view, I really don't know. Anyway, in theory I suppose that the very best prime should always be better than the very best zoom if only because there'll be the likelihood of tighter tolerances and it being closer to the design ideal but I suppose that it's likely that mere mortals like us will never or rarely see the difference between decent primes and the best zooms in the real world.

I may be wrong but I think that diffraction is a property of light and therefore constant. A higher pixel density will therefore just make diffraction visible earlier than a lower pixel density. Maybe.
 
blinkerz said:
Interesting comparison.. wondering does diffraction hit zooms quicker than primes..
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No. It's a function of the diameter of the aperture relative to magnification. It is always present, and diffraction has least effect at maximum aperture (lowest f/number) but other aberrations are reduced by incvreasing f/number so you only see the impact of diffraction when it overtakes the relative improvements casued by stopping down.

As I say, in practise the best lenses peak around f/5.6 on crop format and f/8 on full frame. The higher the quality of the lens, the lower the f/number it shows, but the higher the peak.

malla1962 said:
I think its more to do with pixel density.
http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm
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That theory is often put forward. But in practise, higher pixel density always delivers better sharpness. I think it's a red herring TBH, but I'd be interested to see any real evidence to the contrary.

woof woof said:
Primes are designed for one angle of view whereas zooms obviously aren't although I suppose that a zoom could be designed to be at it's very best at a particular angle of view, I really don't know. Anyway, in theory I suppose that the very best prime should always be better than the very best zoom if only because there'll be the likelihood of tighter tolerances and it being closer to the design ideal but I suppose that it's likely that mere mortals like us will never or rarely see the difference between decent primes and the best zooms in the real world.

I may be wrong but I think that diffraction is a property of light and therefore constant. A higher pixel density will therefore just make diffraction visible earlier than a lower pixel density. Maybe.
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That is true in theory, about primes vs zooms. And if you had say a 100mm f/4 prime against a similar spec zoom, the prime should be capable of better performance.

However, what designers tend to do now is trade zoom range for low f/number as nobody would buy an f/4 prime and zooms are pretty good down to f/2.8. Hence 135mm f/2, 85mm f/1.2, 35mm f/1.4 etc. It was different twenty years ago when 35mm f/2.8 or 135mm f/3.5 was quite common.
 
That theory is often put forward. But in practise, higher pixel density always delivers better sharpness. I think it's a red herring TBH, but I'd be interested to see any real evidence to the contrary.
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I think that is true, the diffraction does kick in, but not to an extent where it makes the image less sharp than it would have been at the lower resolution. There is obviously the point about whether the extra resolution is giving you extra detail for a given lens, but this is a property of the specific lens and how sharp it is rather than anything to do with diffraction.

As to primes vs zooms, well, yes, in general, but it isn't always true.

An example is the Zuiko 50mm macro lens. DPReview reckons it is one of the sharpest lenses they have ever tested - it is seen as the benchmark of macro lens on cropped sensors by them (check out the DPReview of the Canon 100mm f2.8 USM IS L Macro and what they say about it in comparison with the 100mm on the APS-C bodies).

However... The 150mm f2 is sharper and, interestingly, so is the 35-100mm f2 zoom lens - this lens also has higher MTF ratings than the 300/2.8 too - also considered to be one of the sharpest 300/2.8 lenses available.

So there is general truth, but some counter examples too! ;)

Andy
 
"It was different twenty years ago "

I'm not so sure. I don't think that the better primes are compromised in the chase for wide apertures. I think that lessons have been learned over they years and that it's now possible to make both better primes and better zooms than ever before but I think that the theoretical superiority of primes is probably as true now as ever. I still think that us mortals probably wont see too much actual superiority though but I've no doubt that it's there for the very skilled.
 
woof woof said:
"It was different twenty years ago "

I'm not so sure. I don't think that the better primes are compromised in the chase for wide apertures. I think that lessons have been learned over they years and that it's now possible to make both better primes and better zooms than ever before but I think that the theoretical superiority of primes is probably as true now as ever. I still think that us mortals probably wont see too much actual superiority though but I've no doubt that it's there for the very skilled.
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I'm not sure there's actually too much disagreement there ;)

Lens design is a compromise. The three main factors that are at odds are focal length range, low f/number, and format coverage - you can't have all three.

Size/weight and vignetting are other factors, and compromising everything is of course price. However, regardless of cost, it is currently just not possible to make, for example, a 24-85mm f/1.4 zoom with anything like acceptable performance. It would be impossibly huge, with severe vignetting and hopeless sharpness at the edges. But split into three, you can have excellent 24/35/50/85mm f/1.4 primes.

In practise, the widest range zooms have high f/numbers (not to mention vignetting, distortion, too much CA and pretty average sharpness). The lowest f/number lenses are all primes. The only f/2 zooms are Olympus and they only have to cover the 4/3rds format that is one quarter the image area of full frame.
 
woof woof said:
"It was different twenty years ago "

I'm not so sure. I don't think that the better primes are compromised in the chase for wide apertures. I think that lessons have been learned over they years and that it's now possible to make both better primes and better zooms than ever before but I think that the theoretical superiority of primes is probably as true now as ever. I still think that us mortals probably wont see too much actual superiority though but I've no doubt that it's there for the very skilled.
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Theory and practise are quite different. It is quite possible to make a zoom lens that is sharper at its maximum aperture than a prime at the same aperture. It depends on which zoom and which prime. :D

I've been hiring/trialling the Zuiko Digital 35-100 f2 over the last week. I would be very, very hard pushed to find a prime at 35mm or 100mm at f2 that was sharper. My 50-200 is very good, but not in the same league as the 35-100 for sharpness wide open (and a very wide open it is).

I own the 14-35 f2. I bought this because I wanted the practicality of the zoom but the performance of a prime. I replaced my 12-60 f2.8-4 with it (which DPReview described as "Indeed the Olympus Zuiko Digital ED 12-60mm F2.8-4.0 SWD is quite simply a superb lens, which can lay claim to being one of the very best standard zooms currently available.") - and it is better than that.

This all comes at a price, the 14-35f2 and the 35-100f2 are about £1500 each - not cheap. But then I see the price of the new Canon 70-200 f2.8 IS L II and they don't look so bad...

Andy
 
HoppyUK said:
he only f/2 zooms are Olympus and they only have to cover the 4/3rds format that is one quarter the image area of full frame.
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If they could cover the full-frame area, they would be massive - as they would also need to be double the focal length to roughly equivalent.

Andy
 
In a word-yes, although mentioned that you would be unlikely to see a quality difference at that aperture, low f number primes generally focus faster than zooms, and are better at finding focus in low light.
 
No optical qualities any more. Size, weight, Dof and Bokeh.
 
Les McLean said:
In a word-yes, although mentioned that you would be unlikely to see a quality difference at that aperture, low f number primes generally focus faster than zooms, and are better at finding focus in low light.
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Part of that is that the mass of the bit of glass the focussing motor is moving is generally a lot less, also more light is hitting the AF sensors.
 
Cheng said:
No optical qualities any more. Size, weight, Dof and Bokeh.
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incorrect, the optical quality is better even of the best of zooms but its just so hard to notice after a while due to lens designs and remember makers will eventually update their primes and the quality will then bet even the likes of the 24-70mm and 70-200mm.

also the optics in the prime are much better as there is very little distortion ~0.3% average on prime compared to ~3.6% average on a zooom. also remember that the clarity is better due to the few optics.
 
Sharpness is often used to compare lenses and often becomes the benchmark to determine which lens is the better one, however there are many qualities that make a good lens, not just sharpness. Contrast rendition, resolution, bokeh, etc all play their part in determining how good an image looks and they all combine together to give a top lens its special quality and often it's hard to quantify, rather when you see an image taken with one of these lenses it just "looks" better.

Paul
 
Woofmix said:
Sharpness is often used to compare lenses and often becomes the benchmark to determine which lens is the better one, however there are many qualities that make a good lens, not just sharpness. Contrast rendition, resolution, bokeh, etc all play their part in determining how good an image looks and they all combine together to give a top lens its special quality and often it's hard to quantify, rather when you see an image taken with one of these lenses it just "looks" better.

Paul
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Very true, some lenses just have that certain something...

I know I'm preaching to the converted with you, Paul... ;)

Here's one I took with the 35-100 before I sadly returned it yesterday...

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100% crop:

_X300029-260.jpg



Taken wide open @f2, 35mm
 
Testing my Nikkor 50mm f/1.4G against my Nikkor 24-70 f/2.8, with the zoom at 50mm and both lenses at f/8, I was pleasantly surprised to find that the IQ was indistinguishable from one to the other.
The IQ wasn't visibly degraded as I zoomed in or out either, compared to my original.

My Nikkor 70-200 f/2.8 VR-I will be checked against 'my' Nikkor 85mm /f1.4 (when I finally get hold of it - it's in the post as we speak, hopefully!!!).

My own little in-house test has finally banished my own preconceptions that zooms are always inferior to primes. Though you'll probably have to buy the latest and most expensive for it to be always the case, I think...
 
mastertrinity said:
also remember that olympus dont actually have the depth of field for f2 on the zoom because they dont make FF and so the DOF is only equal to f4 (2X crop factor)
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The Oly lenses have the speed advantage of the larger aperture but the increased DOF due to the crop factor, this is true and when using telephoto lenses is usually an advantage as the very shallow DOF of a tele lens means a smaller aperture needs to be used in some cases to give sufficient DOF thus Oly are 2 stops ahead of ff in relative DOF.

Paul
 
That's true - shallow DOF is one thing, but you can have too shallow! For wildlife and macro, more DOF is advantageous. An example would be using a 300/2.8 on full-frame. @2.8, the DOF is often too small to get sufficient of the animal being taken in focus. If you look at the BBC wildlife photographer of the year images, many are with the ubiquitous 300/2.8 focal length/aperture lens. However, on full frame, none of them are shot wide open - almost always at f4 or f5.6.

Crop sensors are not the ideal kit for artistic portrait shots - but can be the best for wildlife, where sufficient DOF and the extra reach are key.

Having said that, I don't often find the bigger DOF limiting - you can get nice effects if you are sufficiently close to the subject. It's just with FF, you can get shallower more easily.

DOF is somewhat subjective anyway - and does depend on how much you enlarge or crop an image (these are assumptions used to set a standard circle of confusion radius).

Fourthirds sensors are a different aspect ratio to all other popular DSLR formats (4:3 vs 3:2). The relative diagonal distances are often used to avoid the problem of the different aspect ratios - hence fourthirds is half that of full-frame over the diagonal.

If you are typically producing images that are 4:3 aspect ratio (go round an art gallery and you find that more pictures are nearer to 4:3 than 3:2), with full-frame or APS-C, you end up lopping off the long ends of the picture. So, in extremis, the comparison with fourthirds can be argued that it is better to look at the relative sensor heights, rather than the diagonal. This gives a factor of about 1.8 rather than 2. This argument is somewhat contentious, but it at least uncovers the point that DOF is not simply a matter of sensor size. In any case, 1.8 and 2 are quite close, as is 1.6 or 1.5 - in reality, you don't see much practical difference in DOF between fourthirds and APS-C cameras.

Andy
 
mastertrinity said:
incorrect, the optical quality is better even of the best of zooms
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Not anymore. 24-70 2.8 vs 50mm 1.4....they're pretty much identical. And try telling that to the 14-24 people... :thumbs: unparalleled by pretty much any other optic, prime or otherwise..
 
Cheng said:
Not anymore. 24-70 2.8 vs 50mm 1.4....they're pretty much identical. And try telling that to the 14-24 people... :thumbs: unparalleled by pretty much any other optic, prime or otherwise..
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Agreed, see my earlier post...
 
My only zoom is a Sigma 10-20, the rest are primes, and I'd say all but one (a cheap telephoto) are sharper than the Sigma regardless - and yes, my Sigma is already sharp!
 
ive been researching into this as originally i was going for a 50/85/100 prime set up and after reading some of the comments i realised that zooms can be useful and so its good to have a mixture.

of course, loads of togs will love to shoot all in primes but alot of the work will not allow it due to lack of flexibility. pretty much any consumer zoom will be beaten by a prime, however when it gets to the big guys like the 24-70mm its hard to tell the difference and so alot of togs will only keep the 50mm for its low light and dof capabilities (like arkady said).

i can cope with just a 50mm f1.4 for portraiture and a 90/100mm macro for flowers and thats the basics of what i can cope with, all the others such as the CZ 85mm f1.4 and the 24-70mm will just be a bit useful to fill the gaps. so as you can see its all dependant on the togs needs, some photographers ive met will claim "give me a body and a 50mm lens and im happy" which can be perfectly acceptable especially as sometimes we use zooms to be very lazy.
 
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