Are different lenses actually that different? Comparing three 50mm lenses

Which of the many lenses that flood the market is the best for your needs?


The range of options, for most any brand, can go from the price of a drink, for a vintage lens, to the price of a small car, for top of the line, cutting edge technology, new ones.

And obviously there is a whole spectrum of alternatives between these extremes.


But what justifies the different prices, and how different are different lenses once we compare them in the real world? 

Although there is no lack of information online, it can still be hard to make up your mind, especially if you are new to the world of photography, or if you get sucked into extremely in-depth pixel comparisons, which are definitely useful and informative, but don't really give you a feel of how the lens will actually perform in real life, in "normal conditions".

Or maybe they do, but I had a pretty free afternoon, today, so I thought I would run my own test on a few lenses I have, and see what results, if any would emerge from a comparative test.

So fasten your seat belts and sit tight, because today we are comparing three 50mm lenses and trying to extract some info that might be useful.


But first things first, lets talk about samples and "methodology".


The lenses I am comparing today will be:

  1. The Pentax "kit lens", an 18-55 mm zoom with a variable fastest aperture of f3.5 to f5.6
  2. An old Pentax 50 mm f1.7 (k-mount)
  3. The Tamron 17-50 mm f2.8

I chose these lenses because they seem like a good sample of what most photographers will have in their own home or studio, so my guess is that most people will be able to relate with a selection of lenses that is similar to this one, which is the whole point of a comparison, in my opinion.


So let's get a closer look at the contestants.



First in line is the Pentax kit lens. It has very similar technical specs as any other kit lens from any other brand.


It's not a fast lens, as mentioned earlier, and the widest aperture available at 50mm is f4.5, a setting that will not win you any bokeh or creamy blur competitions.


It feels rather light and cheap, but also well assembled. While it's mostly made out of plastic, it's not excessively flimsy and can take a bit of a beating without too many issues. 


Also, to the credit of Pentax, it has at least some weather sealing, in the form of of a ring around the mount, which add a little bit of protection from the elements.


This lens, should you want to buy it, will cost anywhere between 40 Euro (for a second hand version without weather sealing) to around 170 Euro (for a new lens with weather sealing).



Second comes a really cool lens, in my opinion.

It's a 50mm prime with a fast speed of f1.7.


It was a good lens, in its time, and you can feel it just by picking it up. 

It's almost completely built out of metal and the focusing ring is smooth and has a lot of travel, making precise focusing rather easy.

It feels solid and well built, although I would try not to drop it.


On a modern DSLR, it looks, and is, very compact, making it a great choice to take around for a walk in the city.


Obviously this lens is manual focus only, so that is most definitely something to take into account.

You can find this lens for anywhere between 20 and 50 Euro, in my experience. 



Last but not least is the only non-Pentax lens in this comparison.

I'm talking about the Tamron. This 17-50mm lens has a constant fast aperture of f2.8, which is reall a great thing to have on a zoom lens, in my opinion. 


The build is mostly plastic, but it's heavy and solid, with no serious give at the joints, and it feels like a serious, well built piece of gear.

I would still not recommend dropping it, though.


This is the most bulky lens of the lot, and the heaviest, by far, although that sweet f2.8 is definitely worth the weight, in my opinion.


It's also the most expensive, and will set you back around 350 Euro if you buy it new, and somewhere in the 180 Euro range, for a used one.


Ok, so now that we met the contestants, let's set them all to the 50mm focal length and see how they perform against each other.


I don't have a professional testing setup, as the ones you find on the bigger websites that review and test gear, but I also think this can be a strength, because most users are not dealing with graphs, extreme enlargements and pixel comparison, but they might just want to know if that lens they saw at a flea market for ten bucks will perform any better or differently from the gear they already have, or if it's a waste of money.

Or they might be on the fence about upgrading from a kit lens to their first more serious glass, and might want to get a better understanding as to what the differences will be, and there are so many opinions online, often not backed by photos or proof, that it can be a little daunting to make a choice.


Based on these considerations, I decided to setup a very easy comparison, something that could easily be reproduced by anyone, and also give a visual, "photographic" comparison of the various lenses and how they perform. 

There are a lot of other, similar, resources online, and should you be looking to make up your mind on a lens, I encourage you to check out as many of them as you can.


Anyway what comparisons did I try out?


I used my old Pentax ME as a model. I set it on my couch, by the window, and set a tripod on the floor in front of it, so that I would be able to change lenses and settings without altering the position of the camera too much.


I decided to start out with the lowest possible setting which all three lenses could share, which, for obvious reasons is the f5.6 aperture of the kit lens. 

I decided to use a value of ISO 100, because I wanted the work to be done by the lens, rather than the camera, and I settled for a shutter speed of 1/50 to keep in line with the "rules" to cut down on shake blur when shooting hand-held photos.


I used manual focus for all the photos, and I used the "1.7" mark on the lens as my focusing point.

All images are unedited and untouched, except for the last set, which I edited because, ultimately, that is what happens to all photos, so it's kind of relevant, I would say.


All these variables are arbitrary, of course, but they still enable us to see what differences, if any, these lenses will show with normal use.


So with all this intro, it's time for a little less conversation and a little more photos, time to compare!



Let's consider this the benchmark image for all three lenses. 


As I mentioned earlier, these are all shot at f5.6, ISO 100, 1/50.

Starting from the left is the vintage Pentax 50mm, the second is the Pentax kit lens, and the third is the Tamron.


Considering they are all shot at the same settings, it's not too surprising that the images are not too different, though the Tamron does seem to be a little darker than the other two, while the kit lens does seem to be just a little lighter than the others.


There are a few other things to be noticed, however, the first being that all three lenses frame the image a little differently. 

The vintage Pentax flattens the image more, and brings the subject closer to the viewer, while the Tamron takes a bit more of the surrounding space into the frame, with the kit lens being somewhere between the other two. 


In terms of color, aberrations or other such qualities, I don't see a huge difference between the lenses. In terms of focus, however, there are a few observations to be made. 

Considering the focus point on the front of the lens, it's normal that there would be some blurring moving back in the image, but all three lenses perform quite differently in this aspect.

The Tamron, seems to be a clear winner here, with the logo on the camera body being equally in focus as the lens, and quite crisp and contrasty.

The Pentax prime lens performs well enough, but there is some noticeable blur on the camera body, not necessarily a bad thing, but definitely more evident than the Tamron.

The kit lens is the one that displays most blur on the camera body, and is also has the lowest contrast. 

Again, I want to point out how blur is not an issue in itself, as you might be very well wanting to have a nice, soft, fallout from the point of fucus, but in terms of comparison, the kit lens definitely does not perform as well as the other two.



This next comparison is a little more arbitrary, as I decided to see how the different lenses would perform at their fastest aperture, but as the range goes from f1.7 to f5.6 I had to change a few other settings too, in order for the images not too be blown out.

So are the results.


In the case of the Tamron I did not make any changes if not setting the aperture to f2.8, while with the Pentax prime I increased the shutter speed to 1/160 to compensate for all the extra light coming through the lens after setting the aperture to f1.7.

Since I could not use a faster aperture on the kit lens, I bumped up the ISO from 100 to 400. 


 In terms of exposure all three images are pretty balanced, with none of them sticking out too much, but what is interesting to me, in this case, is how dramatic the change in the depth of field becomes. 


While the Tamron blurs gradually and "elegantly", the Pentax prime has such a shallow depth of field that the knobs on the camera body are barely recognizable.

The logo on the camera is also much less readable than in the Tamron photo, and there is clear chromatic aberration on many of the edges, which the Tamron contains better while having better contrast.


Again, it's a matter of preference which one you prefer, and they have not been edited, so that also counts for something.


Last but not least is the kit lens with enhanced ISO sensitivity.


Now that we are looking at photos with more controlled blur, its relatively poor performance in the previous comparison becomes a strength (in a way), as it offers a pleasant fallout from focus to blur, with the higher ISO setting helping to blow out some of the highlights, contributing, in my opinion, to give an nice illusion of blur. 

The color also appears to be warmer, slightly leaning into the yellows rather than the blues, while the other two are a little colder, with the Pentax prime having the coldest color temperature.

There is no noticeable ISO noise, even once the photo is enlarged quite a bit.


But really, what is photo without at least some basic tweaking of contrast and, saturation and white balance?

So let's see how these lenses perform in the most ultimate sense. What pictures will they produce once we are done editing them to out liking?


Let's see...




The three images above are simply lightly tweaked versions of the previous set.

To edit these images consistently, and given the fact that the originals were not too dissimilar, I made all changes on one of the images, then copied the settings to the other two.

As for what I changed, I increased contrast by altering the settings for highlights/shadows and white/black, then I added a touch of clarity and vibrance, because that's how I like it.


So what's the result?

Not too different from before, I would say, in the sense that the hard aspects of all three pictures (focus, depth of field, blur...) have not changed, but all three images are definitely richer in color and texture now.


But is there a winner?

Not really.

All three images are more than acceptable, and which one you choose really depends on what little aspects you value as more appealing.

If you like shallow depth of field and heavy blur you will choose the first. If you like other aspects you will prefer one of the other two.


Does this mean the differences between these lenses are so small they are irrelevant?

Why the price difference, in that case, and most of all, which lens is best for you?


In absolute terms, in a controlled environment and in optimal conditions, yes, these lenses all perform reasonably well, and none of them is truly garbage (looking at you, people who suggest to swap the kit lens right away, because you NEED good glass to take good pics...)so you should never feel like a lens is too shitty for you to use.


The keywords are, however, "optimal conditions", and most of the time we are shooting in conditions that are not optimal at best.


Suppose you are in a badly lit place. Suddenly your f5.6 might not be even close to letting in sufficient light to take an acceptable photo. Sure, you can bump up the ISO, but depending on your camera and on the conditions you are shooting in, there will be a hard limit to what you can do before you get unacceptable amounts of noise.


Then again, it's not all about aperture.

While two of these lenses have autofocus, one of them is fully manual. This means you will probably not be taking it to shoot a concert or any situation in which being able to quickly and safely change your focus is a necessity.


Versatility and size also come into play.

Are you ok with having one, fixed, focal length or do you think you might need, or want, some variety?

Are you trying to be a discrete street photographer or is that irrelevant to you?


As the photo below shows, these lenses, which produced pretty consistent images during this comparison, are very different once they are set to 50mm.



There is a reason for each of them to be the way it is, as there is a reason if one costs 20 Euro, while another one costs 350.

The difference, however, has less to do with absolute quality, and more to do with how each lens fits your specific needs.

No amount of money will guarantee that your photos will be good, and the shittiest gear will not prevent you from taking photos you are happy with, provided you know what you are buying, and what strengths and weaknesses it has.


Which one is right for you depends on how well you know your needs and style, but one thing is for sure, if you know what you want and know what you are doing, every one of these lenses will be able to produce results that will satisfy you, and even the infamous kit lens will have something to prove.