Comparing a zoom and a prime lens

[Richard Donham]

I have a Tamron 17-50 mm, f/2.8 non-VC lens and a Canon 50 mm, f/1.4, and decided to compare the two, because I don't need more clutter in my life and I was thinking to sell the Canon. I have read the numerous lens reviews and was thinking to see if I could see the sometimes mentioned benefit of a prime lens.

So, I took a series with my camera mounted on a tripod, same subject (a cluster of orchids), in the same light (indoors, using window light). In aperture priority mode, I shot at ISO 100, f/4, 5.6, 8, and 11. Anyway, the result was that all of the zoom lens photos were slightly smaller (I didn't move the tripod) at 50 mm than were the prime--I am thinking that the Tamron is really about 45 mm at 50 mm. And, all of the Canon photos were about 1/2 ev darker, as a result of the shutter speed being consistently less on the prime. Not sure why this is. Otherwise I couldn't tell you, in a double blind comparison, which lens took which photos.

So, I guess my question is--in general, is there an appreciable difference photogenically between the images produced by a decent prime and an equally decent zoom? I can't imagine that there is. If the manufacturer has good QC of the complexities of moving the lens groups about inside the lens, it seems to me that they must produce images indistinguishable, whether they are from a zoom or a prime. But, maybe I am missing something.

[Markvetnz]

People always said primes were better than zooms and until recently that was probably true. However, IMO, the new zooms can produce photos as good. I have a Canon 70 to 200 2.8L IS II and it is by far my favourite lens. The images are stunning and you just can't beat the versatility of a zoom. I also have a Canon 85mm 1.2L (supposedly "The Portrait Lens") and I use it far less than the zooms I own. It can produce brilliant images, but so can all my other lenses.

My only exception is my 400mm F2.8L. It is a squillion times better than my 100 to 400 5.6, but then it costs a squillion times more too. If money is no object then owning a few primes is a little luxury you can afford, but if I had to only have 1 or 2 lenses, they would both be zooms.

[Colin Southern]

Hi Richard,

As a rule of thumb, a high-quality prime will have a noticeably higher image quality than a high-quallity zoom - BUT - (<- note: that it's a "BIG" but) - you'd have to apply correct capture sharpening to both and then examine them at 100% magnification (where 1 image pixel corresponds to 1 monitor pixel). If you're trying to evaluate the image quality by looking at the entire image at once on your screen (ie "as one would normally look at a photo"), then you won't see any difference.

In many ways it's a bit like asking "Is a 430km/hr Bugatti Veyron a better car than a 350km/hr Ferrari Enzo", when all you want to do is drive to the corner dairy. The reality is that either vehicle is "more than adequate" for the job.

So in theory and in practice the prime is sharper, but for real-world shooting, primes and zooms are both more than adequate. I might add that I have both the EF85mm F1.2L USM II that Mark referrs to - and an EF70-200 F2.8L IS USM II - and it's the latter that's on my camera most of the time for bother studio & location shoots (and even a lot of landscape); you just can't beat the versatility of a zoom.

Just to give you a hint at what a good prime is capable of though, take a look at the 100% crop taken from an image shot with an EF85mm F1.2L USM II -- it really doesn't get any better than this ... Try as you might, you won't get this level of performance out of any zoom that I know of - but then again, who cares

(be sure to click on the image so you're viewing it at 100%)



This is the image is was taken from ...



In terms of the differences you're getting with exposures - yes - it does happen. Basically, the amount of light that actually makes it through to the sensor is always a bit less than what should make it through in theory. The reasons are somewhat involved, but the short answer is "just don't worry about it". In my experience it's pretty typical to have to add about 1/3 to 1/2 stop of exposure compensation to fully compensate.

[Richard Donham]

Thanks, Mark. There is no substitute for good glass, be it prime or zoom.

[Richard Donham]

Thanks, Colin, good points, all.

[rpcrowe]

I consider my 70-200mm f/4L IS and my 17-55mm f/2.8 IS lenses to be top-line glass which will allow me to produce excellent images.

A top-line prime will also produce excellent imagery but, how much better imagery do I need than my two zooms provide? The answer is that I don't need better quality imagery! I can make large blow-ups from images shot with either lens.

If a person has used top-line zooms and then feels that he or she requires better better imagery than can be produced from those top-line zooms, more power to that person. However, if a person has been using lenses of medium quality such as the various kit lenses or some extended range zooms and is not particularly satisfied with the quality of the imagery produced, switching to a prime is NOT THE ONLY SOLUTION. Try using a top-line zoom for shooting.

By the way, in answer to Richard's comment regarding the focal length of his Tamron zoom; zoom lenses are only the listed focal length when the zoom is focused on infinity. Don't worry about the lens shooting at 45mm when it is on 50mm...

[Snarkbyte]

While I largely agree with what has already been said, it may be worthwhile to point out a few areas where primes are still significantly better than zooms... and not just in the sense of pixel-peeping. A few fairly common areas are:

1. Macro shots - zooms just don't focus close enough for even an approximation of macro, so primes are the only real choice here
2. Bokeh - Undesirable bokeh effects of zooms are mitigated (and practically eliminated in many cases) with a crop-sensor body, but primes still have a significant and noticable advantage over zooms for full-frame sensors, especially near the extremes of the zoom's focal range.
3. Vignette - What I said about bokeh pretty much applies to vignette as well.
4. Speed - There are some excellent fast zooms available (the Canon 70-200 f/2.8 IS comes to mind...), but generally speaking, if you need fast glass and high IQ, primes still have the advantage over zooms.

Whether any of these areas are important enough to justify the cost of a prime over (or in addition to) a good zoom is entirely up to the individual, but they are important factors for many photographers. I could, of course, make a list of advantages of zooms over primes, but that's already been covered fairly well in previous posts. JMHO

[Colin Southern]

Hi Al,

Not so fast ...

1. Macro shots - zooms just don't focus close enough for even an approximation of macro, so primes are the only real choice here

When I add my Canon 500D Closeup adator to the front of my EF70-200 F2.8L IS USM II I get 1:2 macro - and if I also add a EF2.0x Teleconverter I get 1:1 Macro using a zoom Extension tubes also get one closer.

2. Bokeh - Undesirable bokeh effects of zooms are mitigated (and practically eliminated in many cases) with a crop-sensor body, but primes still have a significant and noticable advantage over zooms for full-frame sensors, especially near the extremes of the zoom's focal range.

I don't think it's that big a deal to be honest - this was shot with an EF70-200mm F2.8L IS USM II + EF1.4x Teleconverter @ 240mm (so close to the end of the zoom range), and the Bokeh looks just fine to me. In my opinion it's more about the ratio of camera-subject-background distances.

3. Vignette - What I said about bokeh pretty much applies to vignette as well.

Vignetting is pretty much a non-issue these days - it's usually quite minor and easily correctable with any post-processing package (often automatically).

4. Speed - There are some excellent fast zooms available (the Canon 70-200 f/2.8 IS comes to mind...), but generally speaking, if you need fast glass and high IQ, primes still have the advantage over zooms.

Speed and IQ don't go together ... for sure, primes are available in faster speeds than zooms - and it's primarily for this reason that I think of primes as specialist lenses; whether or not one can actually use that speed (and often it's resulting extremely narrow DoF) is another story though. In terms of image quality, although a given prime in a given segment of the market will generally be sharper at 100% magnification than it's equivalently positioned zoom, I've get to see an example where it makes any difference in a real-world image; certainly any advantage would long-since be sampled out if the image were displayed at typical internet resolutions -- arguably it could be seen in a real-world print, but it would have to be a pretty big one (and examined at "nose length").

Just my 10c worth! (and I might add, coming from a guy with more primes than zoom - but the zooms get used one heck of a lot more).

[Dave Humphries]

I have a Tamron 17-50 mm, f/2.8 non-VC lens and a Canon 50 mm, f/1.4, and decided to compare the two, because I don't need more clutter in my life and I was thinking to sell the Canon. I have read the numerous lens reviews and was thinking to see if I could see the sometimes mentioned benefit of a prime lens.

Hi Richard,

I don't want to enter into the pixel peeping quality issues, just highlight the fundamental difference between two lenses you already own, (so I'm not considering how much each costs to buy, or which is better). Al (snarkbyte) has mention this aspect and Colin has responded.

At 50mm, the Tamron is f/2.8 maximum, but the Canon is f/1.4, 2 whole stops wider - not for low light considerations, but for slim depth of field considerations, sometimes, you don't want a lot of DoF. It is probably a smaller, less obtrusive lens too.

That said, I have heard Colin say before that his 85mm, f/1.2 is virtually unusable at that f/1.2 wide an aperture in portraiture because you'll end up with only one eyelash of one eye in focus (OK, I might be exaggerating, but not by much)

However, at slightly longer distances, the lack of DoF can be useful - I am particularly in mind of Thierry's (tb72) show jumping (horse) shots, although many of these are at longer focal length than 50mm, it is true.

JMHO,

[Colin Southern]

That said, I have heard Colin say before that his 85mm, f/1.2 is virtually unusable at that f/1.2 wide an aperture in portraiture because you'll end up with only one eyelash of one eye in focus (OK, I might be exaggerating, but not by much)

Hi Dave,

The other problem that people often don't appreciate is that if you're trying to use it outside @ F1.2 you run into problems with insufficient shutterspeed.

Assuming 100 ISO 1/100th @ F16 -> 1/200th @ F11 -> 1/400th @ F8 -> 1/800th @ F5.6 -> 1/1600th @ F4.0 -> 1/3200th @ F2.8 -> 1/6400th @ F2.0 -> 1/12800th @ F1.4 and even faster at F1.2 - many cameras won't go above 1/4000th and I don't know of any that go faster than 1/8000th.

I know that people do use them creatively, but I'm just not one of them! To be honest, unless one "nails it" often these "creative" shallow DoF images - to me anyway - just look like badly focused shots.

[rpcrowe]

Can I separate the subject from the background using selective focus with my 70-200mm f/4L IS lens? Sure I can...

Along the above lines... using a 200mm lens at f/4 on a 1.6x camera; your DOF is the following when focused at:

10 feet = .11 feet or 1.2 inches
20 feet = .45 feet or 5.4 inches
30 feet = 1.02 feet
40 feet = 1.82 feet
50 feet = 2.86 feet

A 135mm focal length at f/4 on a 1.6x camera will provide the following DOF when focused at:

10 feet = .24 feet or 2.88 inches
20 feet = .99 feet or 11.88 inches

This is certainly a thin enough DOF to get shots like this. However there is a wide enough DOF not to knock parts of my subject OOF...



Or for a less dramatic selective DOF...

[Colin Southern]

Can I separate the subject from the background using selective focus with my 70-200mm f/4L IS lens? Sure I can...

Absolutely - My biggest problem with DoF is that usually I can't get enough of it!

[Richard Donham]

Thanks to rpcrowe, Al, Colin, and Dave--good points, and an interesting conversation. My take-home message from these comments is two-fold (at least). First, good glass whether zoom or prime, is worth the investment, even for those of us not aspiring to become professional, but just wanting seriously to take better photos. And, second, its important to know the capabilities of my lenses (better than I do), often the difference between a really good photo (several examples above) and another mediocre one is knowing the physics of the lens.

Neither of the two lenses I mentioned is in the same league as the Canon 70-200 mm L lens, obviously. But, I have often been a bit disappointed with the results from shots I have taken with my Canon 100 mm f/2.8L IS macro lens, which is usually reckoned as an excellent lens, all around. Sometimes it does stunning things--but other times, not. So, if I was more careful about depth of field, isolating the subject, stopping down, etc., --that would be the fastest, surest and cheapest way to better photos.

A quote from Ansel Adams that is often used: "The single most important component of a camera is the twelve inches behind it," always useful to keep in mind.

[Anslin]

I am new to the site and forum. Quite interesting thoughts I've read here. It will take me some time learning all the terms in photography, but I'm sure my interest will grow, since I am a very keen novice in photography.

One of the reasons I joined here is to learn more amongst other about the difference between DSLR's and bridge cameras, particalarly the Canon SX20IS.
Is there a significant difference in the zoom ability of mentioned cameras? If one refers to distance. I'm just a normal guy taking his camera along to wherever, but would like to know whether I should opt for a DSLR with up to 300mm lens, or is the SX the better option?

[Dave Humphries]

One of the reasons I joined here is to learn more amongst other about the difference between DSLR's and bridge cameras, particalarly the Canon SX20IS.
Is there a significant difference in the zoom ability of mentioned cameras? If one refers to distance. I'm just a normal guy taking his camera along to wherever, but would like to know whether I should opt for a DSLR with up to 300mm lens, or is the SX the better option?

Hi Anslin,

Welcome to the CiC forums from me - I started with a Fuji bridge camera similar to that model (but in 2007).

It depends what you want to shoot and how serious you are about quality - a fundamental limitation of the SX20IS is there's no RAW capture, which limits how you can post process shots to get best quality.

Budget plays a big part too, the SX20IS goes to 560mm equivalent on the zoom, so a 300mm lens, even allowing for crop factor making that more like 480mm equivalent, is going to leave you a bit short on the telephoto end.

Do you already have the Canon SX20IS?

I think we need to know more before we can advise properly,

[Anslin]

Hi Anslin,

Welcome to the CiC forums from me - I started with a Fuji bridge camera similar to that model (but in 2007).

It depends what you want to shoot and how serious you are about quality - a fundamental limitation of the SX20IS is there's no RAW capture, which limits how you can post process shots to get best quality.

Budget plays a big part too, the SX20IS goes to 560mm equivalent on the zoom, so a 300mm lens, even allowing for crop factor making that more like 480mm equivalent, is going to leave you a bit short on the telephoto end.

Do you already have the Canon SX20IS?

I think we need to know more before we can advise properly,

Hi Dave, thanks for the response. Yeah, I have the SX almost a year now. I'm just a normal homer who likes taking pictures. No background/training whatsoever. I like to be alongside sports fields and stadiums, and like to capture some far-off shots at times. Have taken quite a few sports pics and socials. Sometimes I also take nature.

I must play a lot more with my toy to understand it properly.

Yep, budget played a big role when making a choice/decision.

[Donald]

a fundamental limitation of the SX20IS is there's no RAW capture, which limits how you can post process shots to get best quality.

And I think that's the most fundamental point in the discussion. If you have ambitions to become serious about photography then you must shoot in RAW format, so that you then have a bigger range of options open to you for post-processing work.

I think the discussion about the respective equivalent focal length of lenses is irrelevant. It does come into play if you are discussing two cameras that both can shoot RAW format images. But when it's a case of one can and one can't, then that has to be the primary issue upon which decisions are made. Nothing else.

[Alisa J]

I am new to the forum, an I have consider purchasing some new glass. I currently own the Nikon d40x an the Nikon d7000. I have the zoom lens but another photographer told me in order to get good quality pictures I need to get ride of my zoom lens and purchase the prime lens. What do I do I am so lost right now. I am a new photographer an I'm like there are so many different views on things. Could someone please help me

[Donald]

I am new to the forum, an I have consider purchasing some new glass. I

Hello and welcome to CiC. First thing - Is Alisa your real name? If so, that's great. If not, you can go to Edit Profile and enter your proper name under 'Real Name'. Then it will appear underneath your Username in all your posts. You can also enter your location so that it does the same, just as in my details alongside this message. Then we all know where everyone is in the world.

I hope you enjoy being part of CiC.

As for your question.

What the other person told you would have been true many, many years ago when the quality of zoom lenses was not so good. It would also be true if you intend being anything more than a serious amateur who needs to be able to make very large prints at the highest possible quality. Because at that end of the scale, yes, a top-end prime is going to be slightly better than a top-end zoom.

But if you are like 99.999% of the photographic community are not going to be a top-end professional, then 'no'. What you were told is wrong. Most of us on here use zoom lenses at various ranges (wide-angle; standard ranges; telephoto).

You will get exceptional quality pictures with many of the zoom lenses on the market today. 'How good' is always a matter of interpretation and there are many lens review websites where you can survey technical, objective data measuring performances. Of course, the question of quality also has a direct corollation with money - The more you pay the more you get.

[Glenn NK]

It wasn't too long ago that the STATUS of zoom lenses wasn't too high AMONG PROFESSIONAL PHOTOGRAPHERS. Unfortunately that hasn't changed even though the newer zoom offerings should have put the misconception to rest.

It's interesting to compare several lenses that I have used or own:

Canon EFS 17-55 f/2.8 is in my bag - its resolution tests as done by photozone set some new standards for zooms. It peaks well into the excellent zone, and at worst is in the very good zone.

Canon EF 70-300 f/4-5.6 USM L IS has embarrassed many prime lenses with the MTF tests done by photozone. It peaks well into the excellent zone.

One of the oft recommended Canon primes is the EF 135 f/2 L USM lens. Its best resolution is topped by the 70-300 noted above.

Canon EF 180 f/3.5 USM macro lens - macros are always touted as being razor sharp. Well its best resolution doesn't get into the excellent zone at all.

Canon EF 200 f/2.8L USM II. Its resolution can't keep up with the 70-300 zoom.

I have primes too - a 100 f/2.8 macro and a TSE 24 f/3.5 L so don't take my missives as attempting to put primes down. My real point is that it's time to acknowledge that zooms can be and are, as good as primes - and often better. But old ideas die hard don't they?

Glenn

Anyone can check these tests out at photozone.de (not dot com).