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Why Not Try Out a Prime Lens?

A brief look at primes vs. kit zooms · 11-13-2012 · By PF Staff in Photographic Resources
Why Not Try Out a Prime Lens?

Our favorite zoom is the Pentax-DA 18-135mm F3.5-5.6 ED AL [IF] DC WR - quite a mouthful of a lens name, but we don't hold that against it!

Its focal length rage is ideal for travel photography, as it is basically a lens that can satisfy most everyday shooting needs. Its aperture isn't as fast that of a comparable prime (non-zoom) lens, but given the excellent high-ISO capabilities of modern consumer DSLRs like the Pentax K-30 or K-5, this is generally not a limiting factor.

Vacation Photo w/18-135mm

Photos in this vacation album were shot exclusively with this 18-135mm on a K-5.  We were quite pleased with the results from that particular outing, but how good is this lens really?

We were using the Pentax-FA 77mm F1.8 Limited lens while shooting test photos for a review the other day, so as a little side project, we took a couple of comparative shots with the 18-135mm set to around 77mm, just to see how close this zoom could get to the performance of a prime lens. Much to our surprise given our satisfaction with the aforementioned travel shots, the 77mm did significantly better. It would appear that the 16 megapixel sensor out-resolves the zoom at F5.6, whereas the 77mm handily out-resolves the sensor at both apertures tested.

Lens technologies are ever-evolving, and it can very well be the case that there are high-end zooms out there capable of matching the performance of older prime lenses.  However, if you level the playing field and look at current prime lenses, you can still expect them to generally deliver more sharpness, less distortion, and better overall clarity compared to modern zooms.  And remember, high-magnification "super" zoom lenses will also be a notch below professional or premium zoom lenses that have fixed apertures.

Zoom lenses offer a lot of convenience, but why not challenge yourself to shooting with a prime the next time you go out to take pictures?  You may end up being surprised by the quality of the resulting photos! 

These sample images were shot at ISO 100, in RAW (DNG), with no sharpening and no post-processing. Focus was on the near corner of the building. Click on any thumbnail to download the full JPG files.

Pentax-DA 18-135mm
Pentax-FA 77mm
z 5.6
zoom F11
 100% crop:

 100% crop:

 100% crop:  100% crop:
100% crop: 100% crop:
100% crop: 100% crop:

We hope that these results get you to consider a prime lens!  If you're on a budget, a mere $40 will get you a very sharp lens such as the Pentax-M 50mm F1.7, as long as you're willing to settle for manual focus. 

We believe that the emphasis that camera manufacturers place on kit zoom lenses, especially in conjunction with intro-level DSLRs, is closing a lot of doors for beginners that are interested in learning more about photography.  In addition to offering better image quality, prime lenses will get you to focus more on composition rather than allowing you to document everything around you perfectly, thus they can improve your photography as a result!

PF Staff's avatar
About the author: Various writers regularly contribute articles to the Pentax Forums homepage blog. More recent articles are published under each author's forum username. We hope you enjoy our guides and news coverage!

Tags: prime vs zoom, 18-135mm, 77mm, pentax, lenses

More Posts in Photographic Resources | More Posts by PF Staff

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Robert Cook [Delete] Nov 19th, 2012 10:40AM

The exposures were not the same , The zoom lens is lighter, as shown. If they were the same ,, I am not sure you would see much of a change in sharpness at 100 percent. We really would be stretching a capture if we ever printed at 100 per cent. I always tell my customers that screen sharpness IS NOT final print sharpness ! A print is True . The screen often lies from the final result. So this is not at all a fair test . And post sharpening can change all this again !! Bob

MrCynical [Delete] Nov 14th, 2012 2:43PM

So a travel zoom will produce 'good enough' results for travel photography, while an £850 prime lens will be better? Where would be Pentaxians be without such startling revelations?

In other news, a Ferrari California gets from 0-60mph faster than an Amtrak train!

Thornplayer [Delete] Nov 14th, 2012 1:20PM

Thank you. Good for us less experienced users to see a direct comparison to show the magnitude of the difference.

Mr_Canuck [Delete] Nov 14th, 2012 1:02PM

I subscribe to the theory that a prime lens is not only good discipline and a way to teach yourself a lot about pre-visualizing, it's a long-term solution to creative picture taking. My PentaxForums article The Perfect Zebra Shot in Three Easy Steps references this idea.

And to encourage people who haven't looked past a kit lens to consider primes is very worthwhile.

That said, I don't think this whole sharpness discussion is really that informative or even relevant. Duh, a $800 full-frame prime, when tested well past its widest aperture, vs a $500 superzoom at its widest aperture... yields better sharpness? Thanks for the info. I couldn't have possibly imagined this to be the case.

Only travel pictures? What if you're doing an event? Then again, what if you're travelling up a steep mountain? What if the action is moving all around you? What if it's raining or snowing or dusty? What if you don't know what's coming and want to be immediately prepared? What if you understand where your lens is strongest and shoot to those strengths?

I'll defend the 18-135. It's really a clear shooting lens at 24-70 at any distance, good from 20-115, and good for close-ups at its long end but not very good for distance shots at long end. I think that was engineering's design intent within the realities of physics. Photozone, whatever. The 18-19 range is decent but not great but it's there, unlike with a 50. So you've got a great mid-range zoom with weather sealing, DC motor in a ridiculously small package, a good close-up shooter, and the added flexibility, simplicity and weather/elements sealing of a pretty wide range of zoom. And I'm saying this as one who prefers primes and has at least four of them at any given time.

I know that after every vacation, the first thing I do is come home and look at the corners of all my photos zoomed in as far as possible.

Does nobody have emotional reactions, intuition, or a right-brain related to their photography?

cyclone3d [Delete] Nov 14th, 2012 8:39AM

CarlosU, I didn't say anything before, but yeah, it does look like there is a focus problem on the 18-135 pics. Maybe the camera said it was in focus, but because it is an SLR, it could be back or front focusing. Either correction needs to be entered for the lense, or they need to use a the K-01 to run tests as it will not have front/back focusing problems.

CarlosU [Delete] Nov 14th, 2012 7:20AM

Something doesn’t look right here. I have never written in this forum, but I couldn’t resist.
Am I the only one that sees an evident focus problem with the 18-135 pictures?. Let me elaborate.
When I saw the 100% crops at 5.6 the sharpness of the 18-135 was so bad that couldn’t be explained just by the bad IQ of the lens. So I tried to compare resolution figures of the two lenses (77 limited and 18-135) in the Photozone site, but they tested the 77 with a K10 and the 18-135 with a K5.
So I thought I could get a valid comparison with the DA 70 limited instead (tested with the K5), assuming that the differences between the two limiteds, 77 and 70, shouldn’t be relevant for the case. At 5.6 both lenses are excellent, possibly better for the 77 but not by much.
So this is what I found:
DA 70 limited @ 5.6 center 2698
18-135 @ 85mm and f5.6 center 2430
At these resolution figures the difference in sharpness should be quite less than what is seen in the crops comparison.
Moreover, the crop of the 18-135 at f11 is sharper than the f5.6 one, while the resolution figures in Photozone says the contrary (2430@5.6 and 2297@11). This could only be explained by a miss focus at 5.6 that improves by the added DOF at f11.
Of course, I’m sure the resolution of a limited prime will always be better than that of a zoom at the same focal length and aperture. But in this case, the showed results can be quite misleading and the comparison unfair, don’t you think?

DragonLord [Delete] Nov 14th, 2012 7:18AM

My everyday lens is the DA 18-135mm. Despite the softness in the corners at the long end of the zoom, I don't find the image quality to be poor overall--it is in fact decent given that it is a superzoom lens. But when better image quality or low-light performance is needed, or when I need to get very close, I use my 50mm macro lens.

Prime lenses aren't the only option, and there are several arguments for using a single or few zoom lenses (sensor dust being one of them), but when the highest level of image quality is required, there is no substitute for a prime lens.

pericombobulation [Delete] Nov 14th, 2012 7:09AM

Why doesn't Pentax make all their lenses WR? Or at least make it an option on all their lenses?

mythguy9 [Delete] Nov 14th, 2012 6:49AM

"prime lenses will get you to focus more on composition rather than allowing you to document everything around you perfectly"

Totally agreed! I'm a prime user and will panic if given a zoom!

jimr-pdx [Delete] Nov 13th, 2012 10:02PM

I was hiking with the 18-135 last month, and found myself shooting at 40mm - so off it went & on with the DA40. The zoom hardly got any more use, with 15 28 and 40mm primes taking in the scenery. A month later the superzoom is gone, and a DA70 and SMC-A 24mm are in the bag. I'm happy that I made the shift to more primes.

Alizarine [Delete] Nov 13th, 2012 9:11PM

at what FL was the 18-135 shot? if at 77mm f/5.6 that would be wide-open for the 18-135, while for the 77 LTD it would be in its sweet spot. In such a case, the difference in sharpness will be as high as the cliffs of the Grand Canyon...

I can't call it the performance of the 18-135 sub-par if so.

icy [Delete] Nov 13th, 2012 8:41PM

Answer: Because I don't have money to buy expensive lens!!!

Class A [Delete] Nov 13th, 2012 7:29PM

That's poor performance from the 18-135, as one would expect. The only thing that this lens has going for it, is the WR.

Austrian_Anton [Delete] Nov 13th, 2012 4:28PM

I did a similar comparison with my favorite lenses, the FA limited 77mm and the DA* 60-250mm: There was a difference, but it was not that obvious.
Because this comment cannot contain images, please google: "same background at upper left corner"

Danny Delcambre [Delete] Nov 13th, 2012 4:14PM

I am prime lenses. smile

cali92rs [Delete] Nov 13th, 2012 4:05PM

I know which lens I would tather have in a tropical climate where it rains almost daily.

Asp Explorer [Delete] Nov 13th, 2012 3:58PM

@CDW : Photozone's review has a flaw : it's made in studio, which means at short distance. But a lens' sharpenss depends also on the focusing distance. You can see on Photozone's sample pictures (nice mountains btw) that the 18-135 is a decent lens in real conditions and I would suggest to buy it as a kit lens instead of the 18-55. This said, it's clearly not a stellar performer.

I'm a prime enthousiast and a proud 77 owner, and I can say this lens is splendid. But it's unfair to compare a wide range consumer zoom with a luxury prime. And I don't even mention the 77's price...

cyclone3d [Delete] Nov 13th, 2012 3:27PM

Getting quite a bit of purple fringing even at f11 on the 18-135 I see. I bet if you put a proper hood on it instead of the lame flower hood, it would help it out a bit.

In any case, were thpose pics taken in Tucson, AZ?

neuropol [Delete] Nov 13th, 2012 2:26PM

Thank you for the insightful article. I just recently switched over to Pentax from Canon. I went with a K-5 shortly after experimenting briefly with a K10D. My first lens used was a Pentax-M 50mm f/1.7 - by far the sharpest option I could put on the front of the camera for what we have in stock here at the camera store where I work. It's great that the article has that lens in the shot.

Since then, I've added a 24mm f/2.8 Prime along with an 80-200 f/4 manual focus zoom/macro, and, of course, I still have the 18-55 kit lens, which barely comes out of the gear bag when on a shoot. It seems my go-to has been the 24mm for nice, wide shots (even on APS-C). If I need bit more reach with definitive sharpness, on goes the 50mm, beyond that, it's the 80-200mm.

I sincerely love the fact that old Pentax K mount lenses mount to the K-5 and, with a few settings changes, I hardly notice their not AF lenses at all. With in-camera stabilization, preview modes, and full aperture control with the Lens 'A' mode, the camera just blows the doors wide open to the past and present for lens choices.

I prefer manual focus to AF just about any day unless I require focusing at higher speeds to capture some type of action, which I rarely shoot. Great camera, built like a tank, and being completely backwards compatible with the last 4 decades of lenses is a huge advantage. Not even Nikon can offer the same feature retention with their F mount!

Loving the K-5 and my switch to Pentax. I haven't looked back once since.

mdodrill [Delete] Nov 13th, 2012 1:49PM

I only own the 15,21,40 and 70 because I shoot better pictures with primes. I have always felt that way going back to the ancient film days. The primes just fit my eyes better and I already have the shot framed in my mind before I raise the camera. Just a personal preferance that works for m

DSims [Delete] Nov 13th, 2012 1:32PM

This isn't surprising. I've noticed the K-5 IIs reveals significant IQ and sharpness differences among even the top quality Pentax primes - differences that weren't very noticeable to me with the K-5. It appears to be a simple matter of a sensor that can match the resolution of most lenses.

Warpig [Delete] Nov 13th, 2012 1:02PM

A prime will not only give you better IQ, it will also train your eye into composition. As this a article for newbies, I think that's more important to them.
You can buy IQ, but you can't buy the art of composition.

k9lover [Delete] Nov 13th, 2012 12:50PM

Zoom lenses are great for travel. The main advantage is convenience since you don't have to constantly change lenses. However, any lens whether prime or zoom is worthless if they don't produce sharp images. An all in one zoom like the 18-135mm zoom with better optics and a constant F2.8 or F4 would be ideal if the cost was not prohibitive and the weight was reasonable. I personally use the 50-135 f2.8 zoom in combination with a 15mm and 21mm limited for travel. I find that I’m using the 50-135 more often than the 21mm. The 15mm is seldom used but is a welcome addition when wide angle interior shots are needed

imtheguy [Delete] Nov 13th, 2012 12:03PM surprise which one is sharper but I was interested in seeing just HOW much difference there is. Thats the value of this comparison. Thanks for the article!

yygomez [Delete] Nov 13th, 2012 12:01PM

I wonder if the SMC DA 17-70mm F 4 Al If SDM would be the best compromise for a travel lens

skien68 [Delete] Nov 13th, 2012 11:49AM

All well, but if the sealing is an important feature the 40$ alterntive isn't an option. I wouldn't take my sealed DSLR with that lens to a windy sandy beach. Or out on a rainy photoshoot though I'd like to work with primes, when the climate doesn't cooperate I'll sacrefice sharpness in an instant and prefer being able to use my camera the next day.

tlong423 [Delete] Nov 13th, 2012 9:24AM

What perfect timing, this article.

Last night, I sat down with my wife (who is shopping for a lens and is considering the 18-135mm zoom) while she pored over her favorite digital images over the last few years. With pencil in hand, I was tallying the various focal lengths she'd used to get those images; nearly half the images were at the 18mm mark, then a few at 40-50mm, then a few at 70-77mm, and then a lot at 300mm -- and NOTHING in between those points.

The reason for this exercise was to point out to her that she could probably be much happier getting really great shots from four or five primes rather than settling for lesser quality images from a couple of zooms.

NewTake [Delete] Nov 13th, 2012 7:50AM

Like victordeamorin indicated, this post is not targeted to those who have used a prime lens (hence the title 'why not try out a prime lens). I think we sometimes forget what little we knew when we started out in photography, and that this article may actually help those newbies.
That said, I think it should also be mentioned that one doesnt just choose a prime lens for better sharpness or because you can shoot in low light with a wide aperture. Typically I don't shoot wide open because I have to, but because I want to isolate my subject. Bokeh will typically look much better on primes as well, as well as suffer less from c.a..

CDW [Delete] Nov 13th, 2012 7:47AM

No surprise the 18-135 tested so poorly against a prime. The Photozone website test report and resolution graphs confirm the same findings. It's a mediocre lens at best. Having to stop the 18-135 down to F8 to get adequate sharpness is self-defeating when hand holding the camera. The 16-45 and 55-300 zooms, along with a prime 50mm, would be a better solution unless minimizing weight/bulk for travel is an absolute necessity.

Steve.T [Delete] Nov 13th, 2012 7:37AM

is it fair to compare a zoom walk around lens with a prime portrait lens?

victordeamorin [Delete] Nov 13th, 2012 7:04AM

dcshooter and leopold: somehow I don't think this article is targeted to the enthusiast prime shooter...
Anyway, to the target audience: don't! You'll get hooked up :)

GibbyTheMole [Delete] Nov 13th, 2012 7:03AM

Judging from the photos, it looks like the 18-135 is just an adequately sharp lens. The 55-300 is tack sharp from about 85mm to 300mm... Tamron SP 60-300 (23A) is very sharp at all focal lengths. And the Pentax A 35-105 is prime-like in it's sharpness. Granted, there are more mediocre zooms than really sharp ones, but they're out there. I do enjoy shooting with primes too, though.

Docrwm [Delete] Nov 13th, 2012 6:35AM

It remains a great all-arounder that is WR to boot. Sharpens up around f8 and is very versatile. Add to that the fact that the 77 costs 150%+- and you have a very attractive travel and utility zoom.

dcshooter [Delete] Nov 13th, 2012 6:29AM

Breaking news! Prime lens (and a Limited on eat that) outresolves consumer zoom!

In other news:
Water is wet.
The sky is blue.
The Pope is Catholic.

How could anyone describe this as at all surprising?

leopold [Delete] Nov 13th, 2012 5:29AM

Not a real surprise here, i'm a prime lens shooter, and especially if you compare a kit zoom lens with the FA77Ltd ! No chance for the poor zoom lens.