Looking at the world through 24mm lenses
(equivalent to 35mm with my APS-C camera)

NOTICE: I am not an English speaker, but English is the language that can make this text reach the widest public, so... I'll do my best!

After having tested a number of inexpensive legacy lenses in time (you can find some here), I decided to enjoy the company of a couple of wide-angles, namely the Vivitar 24mm f/2.8 (made by Cosina, according to its serial number, so from now on I'll call it "Vivitar", "Cosina" or "Cosina-Vivitar") and the Pentax-K 24mm f/2.8, that on APS-C almost become "normal" primes.


For some reason, the boss decided that the large blackboard in the office main room must be used for diagrams and other office work, so he brutally detached my lens test targets from it and draw figures about an incoming project right on my test facility!

Too bad, just now that I acquired some new exciting (on-APSC-not-so) wide-angles to check!

I decided to take this not as a setback but just as an opportunity to wander through the city and see how satisfying it is to shoot with this little glasses. Appetite grew, so I also took the camera to the seaside.

I must say that when I used to take pictures with 24x36mm film cameras, I didn’t like much the “standard” 50mm focal length and never even took the 35mm into consideration; instead, I was rather keen on the 28mm length and the 135-150mm range (mostly covered via some cheap zoom).

In time, I changed the way I look at photos and the way I take pictures. On APS-C, a 35mm is more or less equivalent to 50mm for full-frame. Still I don’t like it too much. On the other side, the actual 50mm, that is equivalent to 75mm, is one of my favourite lengths and I still like focal lenghts a bit longer, such as 60-100mm (equivalent to 90-150mm).
But a 16mm (28mm-equivalent, one of my favourites with film) is now most often too wide for my current purposes or taste, and I even use less frequently the 18mm (24mm-equivalent).

Every prime from 27 to 49mm is almost forgotten in the drawer now, unless when I want to shoot with the Zeiss Distagon f/2.8 because I like its image quality soooo much!

Instead, I often find myself at ease with the 23-24mm, equivalent to 35mm.

At the same time, it happened that I found many old 24mm in the 2nd hand shops, and I couldn’t resist!

After some time spent with these items, I must say that I have a strong feeling that most -if not all- of them perform very similarly from the point of trends in image quality according to the distance; this is somewhat sad, and I bet that they copy from the same optical schema.

I mean, it looks like they share a short minimal focus distance, a very handy feature indeed, and that they do good to very well for subjects till 10-20mt away, taking a tremendous penalty, though, at infinity, especially in the corners.

A friend of mine told me that he had the same impression in the past, and that according to him many of these wide-angles are “short of focus” in the distance, in the sense that they could do better if the focus would extend a bit farther, at least to mediate the corners and the center performance, that differ because of sphericity.

So, I have played with some 24mm and some 28mm, too, but mostly with the Pentax-K 24mm (Pentax bajonet, obviously), a Vivitar 24mm (manufactured by Cosina, again for the Pentax) plus a Tokina RMC 28mm (Olympus bajonet).
The Tokina didn’t do well and I am not looking at it here, but the other two are definitely worth mentioning.

One piece of advice first: with the Pentax-K, I used two different cameras: the Pentax K50 (16MP) and the Fujifilm XT-20 (24MP). The latter seems to behave much better with this lens, the sensor is probably thinner or anyway suffers much less from the well-known issues of digital cameras with non-perpendicular rays and wide-angle glasses.

Let's take a stroll

At very short distances, the Vivitar is surprisingly sharp in the center even wide open (did not check the borders), and till 10-20mt is sharp across the whole frame especially if you stop down just a bit. So, given the focal length, on APS-C -never forget!- it is very suitable for street photography and occasionally for portaits, especially of groups.

mid-distance scene shot with the Vivitar 24mm
The image above has been taken with the Vivitar 24mm f/2.8 manufactured by Cosina.
The general quality is very high, especially considering that it’s been recorded by a digital sensor and not on film.

On the right, you can see a 100% crop from the right corner, where you can appreciate the very good resolution. Check how well the wires are defined!
mid-distance scene shot with the Vivitar 24mm, corner detail, 100% crop

The Pentax-K 24mm displays more or less the same behaviour, but, for most aspects, it never excels.

at the seaside, with the Pentax K 24mm
The image above has been taken with the Pentax-K 24mm f/2.8.

Pentax-K lenses are highly praised and often considered superior to the successive Pentax-M variants, though the even later Pentax-A and Penmtax-F usually surpass the previous generations. But just as a rule of thumb.

The sharpness is not very good here, but this is something that I have observed also for the Vivitar with long distances.

And yet, the Vivitar does better in the centre, at least.

In the 100% crop from the right border, the Pentax also shows evident lateral colour aberration, the coloured stripes on the right and left of the white box
at the seaside, with the Pentax K 24mm, corner detail, 100% crop

at the seaside, with the Pentax K 24mm, a diagonal shot to test sharpness
This diagonal shot has been taken with the Pentax 24mm again, with an aperture of f/8.
With such setting, you'd expect some better performance.

Right under, the 100% crops from the top-left, centre and bottom-right.

[and yes, today I have cleaned the sensor from the horrible spot in the centre. Blower and brush were sufficient, lucky me!]
at the seaside, with the Pentax K 24mm, a diagonal shot to test sharpness. Top-left corner
at the seaside, with the Pentax K 24mm, a diagonal shot to test sharpness. Centre
at the seaside, with the Pentax K 24mm, a diagonal shot to test sharpness. Bottom-right

Short distance

What about short-distance performance? Let’s see what to expect from the Pentax...

pomgranate fruits, shot with the Pentax K 24mm
The image above has been taken with the Pentax-K 24mm f/2.8.

Colours are rich and pleasant, contrast is good.

On the right, a detail from the center; you can see that sharpness is very satisfying.

ISO 400, 1/90th of a second.
pomgranate fruits, shot with the Pentax K 24mm, centre detail, 100% crop

And now, flowers with the Vivitar:

You can see for yourself that the bokeh is very pleasant.

flowers shot with the Vivitar 24mm

For more about the Vivitar, you'd better check this page or here.

Now, back to the Pentax:

a rose shot with the Pentax K 24mm
On the right, the 100% crop 5-blades diaphgram manifests its presence in the shape of the bokeh “balls” (which are not balls).
You won't see it in the picture I am posting from the Vivitar because it's been taken with a wider aperture.
The bokeh of both lenses is good, especially given that it is not a characteristic designers where taking much into account for this focal length.

Anyway, I think that the bokeh of the Vivitar is a tad smoother for what I've seen.
rose, shot with the Pentax K 24mm, 100% crop showing the diaphgram blades

A second chance

I took another stroll in Rome, on a warm Sunday of October. I wanted to give the Pentax another try...

Rome, Piazza Navona, shot with the Pentax K 24mm

Well... I can confirm that it's been very easy to shoot with this lens.

Rome, Piazza Navona, shot with the Pentax K 24mm

an alley in the centre of Rome, shot with the Pentax K 24mm

Sparse observations, conclusion

Okay, I must admit that my reviews are becoming rather sloppy. But at the same time, I am trying to enjoy photography as much as possible and this attitude somewhat implies putting aside technical details, unless you really have plenty of time -I don’t!

Anyway, I can conclude that though these lenses are not on par with the modern counterparts that are optimized for use with the digital sensors, they are pleasant to use.

It is rather difficult to use them with scarse light, also with the support of the camera focus-assist, but in plain daylight it is a real joy, especially the Pentax.

Both the Vivitar and the Pentax are well-built, but the latter fares better here, it really lives up the expectations for a sample of the K-generation of Pentax lenses (the first for the K-bajonet).

So, which one would I pick?

For the moment, I really don’t know because the Vivitar-Cosina seems better if not much better in terms of actual sharpness and has minor aberrations, and I feel also the bokeh is a bit better, while ahndling and shooting experience seem more pleasant with the Pentax and there is better control over flare -not exactly a strength in lenses of this class and in the Seventies-Eighties, anyway (see the image below, with veiling produced by the Pentax hit by sunlight)...

veiling with the Pentax-K 24mm, with almost direct sunlight

From the point of view of manual focusing, the resistance of the ring of the Pentax-K is just the right one for my taste, the grip more evident. Also, for some reason, it seems easier to check the focus in the eyepiece. This is possibly just an impression due to the conditions, especially the contrast of the scene, so don’t take my words for granted.

Another possible explanation is that the coatings of the Pentax produce more contrast. Indeed, I think the Pentax K is a bit better in this regard and probably produces more vibrant colours and would also explain the aforementioned flare control.

So, I’d maybe take any of the two for street photography (the Vivitar for its optical qualities, the Pentax for the quickness of use), the Pentax for and group portraits with friends where I don't mind much about quality, but for "real" photography (like when visiting some new place), I’d definitely opt for the Vivitar, because I long for the better sharpness and we've seen that it seems better in most other respects.

Actually, where the Cosina item can compete with the modern offering, the Pentax-K lags behind.

One thing is for sure, now that I know that I like this focal length!... It is so versatile that I want to buy a Fujifilm XF 23mm as soon as possible!

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