Pentax K 55/1.8 vs Pentax A 50/1.7

The SMC Pentax [K] 1:1.8/55 (1975) lens has its roots in the Takumar lenses.

(K 55/1.8 optical design: 6 elements in 5 groups)

It's gone in the M and A series, replaced by the SMC Pentax-M (1977) and Pentax-A (1984) 1:1.7 50 lenses.

(M/A 50/1.7 optical design : 6 elements in 5 groups)

The Pentax K 55/1.8 is sometimes considered to have a more interesting character than the Pentax M/A 50/1.7.

I have both (K 55/1.8 and A 50/1.7) lenses:

And I did some comparisons at f/1.8-f/1.7. The paired shots were taken with the Sony a7c (FF, 24MP) from the same point, but the scenes may differ slightly due to the wind.

1.

(K 55/1.8)

(A 50/1.7)

2.

(K 55/1.8)

(A 50/1.7)

3.

(K 55/1.8)

(A 50/1.7)

4.

(K 55/1.8)

(A 50/1.7)

5.

(K 55/1.8)

(A 50/1.7)

The Pentax A 50/1.7 obviously gives a wider angle of view. The Pentax K 55/1.8 gives a more contrasty image (I think it's the effect of this concrete copy of the Pentax A 50/1.7). The circles of confusion are larger with the K 55/1.8, which is to be expected due to the longer focal length. But I do not see a big difference in the character of the images.

Since I shoot with an adapter, I chose the K 55/1.8 because I like the K-series itself better than the A-series. But when shooting with a Pentax digital camera, the A-series is much more convenient, I would prefer the A 50/1.7 (that I used to shoot with Pentax DSLRs).

See also related notes:

• Pentax K 55/1.8: Samples [2] - FF - f/1.8 (2024-12-10)
• Pentax K 55/1.8: Samples [1] - FF (2024-03-18)
• Pentax K-m vs Sony a7c: Size comparison (2024-03-04)

Image albums:

• Pentax A 50/1.7
• Pentax K 55/1.8

Staeble-Werk Choro R 35/4.5 (M39x1/44): Very rare wide-angle triplet

In addition to the Staeble-Telexon E 85/5.6, I have another lens for the Braun [Super] Paxette II.

The Staeble-Werk Choro R 1:4,5/35 from the 1950s.

But my copy is strange. First, it is not as tiny as I expected after seeing photos of its more famous brother, the Choro 38/3.5. Second, the flange focal distance of the copy is 28.8mm instead of the expected 44mm. I noticed this immediately during test shots.

The letters R (no coupled rangefinder support) or E (coupled rangefinder support) for the Staeble-Werk lens refer exactly to the Braun M39x1 (44mm) versions, while the Leica M39x1 (28.8mm) versions are usually marked with the letter L.

So it is the Braun M39x1 version that is adapted for the Leica M39x1. It has installed an M39x1 extension tube with exactly the right length of 15.2mm:

In addition, an extension is attached to the back of the lens. It looks like a part for the [Leica] coupled rangefinder, but it is not, because its stroke and length do not meet the requirements (for a 35mm lens).

This extension doesn't allow the lens to be mounted on Braun cameras. Unfortunately I couldn't remove this extension, I don't want to break the lens. But I only use the lens with the extension tube 15.2mm, so I left everything as it is for now.

This lens is very rare, I haven't found any mention of it in catalogs or manuals. I've even seen an opinion that such a lens doesn't exist. But it does exist, I've seen modern photos of the lens on the internet a few times, but without any comment. Now I have this lens as well.

I think (because of the name "Choro") it is a triplet: 3 elements in 3 groups. Most likely a Cooke triplet:

And it's not just a triplet, but a wide-angle triplet. A rare thing among interchangeable lenses. 

This is my second triplet lens after the Anastigmat Victar 50/2.9.

The focusing scale is in feet only. The minimum focusing distance is about 2.5 feet (~0.76m). This was a cheap lens, so the entire front part rotates when focusing, along with the aperture ring.

The aperture has 10 blades:

The clickless aperture ring, with marked positions: f/4.5, f/5.6, f/8, f/11, f/16, f/22.

Because the lens is non-retrofocus and slow, it's compact even with the extension tube. It is my smallest 35mm lens:

The lens needed a little repair, but like the Telexon, it is very easy to disassemble, and the lack of coupled rangefinder support makes reassembly easier.

See also related notes:

• My triplet lenses (2024-08) (2024-08-27)
• Staeble-Werk Choro R 35/4.5: Samples [3] - M4/3 - f/4.5 (2024-07-18)
• Staeble-Kata E 45/2.8 (M39x1/44): Standard triplet for Braun Super Paxette II (2024-06-24)
• Staeble-Werk Choro R 35/4.5: Samples [2] - APS-C - f/4.5 (2024-06-13)
• ISCO Iscovitar 50/2.8 (M42x1/45.5): Triplet with simple focusing mechanism (2024-05-21)
• Staeble-Werk Choro R 35/4.5: Samples [1] - APS-C - f/4.5 - "color shift" (2024-05-16)
• Leica M-M4/3 adapter (2024-05-12)
• Staeble-Lineogon 35/3.5 (M39x1/44): Retrofocus evolution of a triplet (2024-04-27)
• Staeble-Telexon 135/3.8 (M39x1/44): The lens for the Braun Super Paxette II (2024-03-26)
• Staeble-Werk Choro R 35/4.5: Lens cap replacement (2024-03-16)
• Staeble-Werk Choro R 35/4.5: Lens restoration (2024-02-03)
• M39x1-Samsung NX adapter (another one) (2024-01-29)
• Braun Super Paxette II BL: Film rangefinder camera (2024-01-13)
• Staeble-Werk Choro R 35/4.5: My experience [3/3] (2023-12-13)
• Staeble-Werk Choro R 35/4.5: My experience [2/3] (2023-12-11)
• Staeble-Werk Choro R 35/4.5: My experience [1/3] (2023-12-09)
• Lenses without cemented elements (2023) (2023-10-12)

Image albums:

• ISCO-Göttingen Iscovitar 50/2.8
• Lens accessories
• Photo
• Staeble-Werk Choro R 35/4.5
• Staeble-Kata E 45/2.8
• Victar 50/2.9

My programmable calculator (1991): Elektronika MK-52

My first programmable electronic device was an Электроника/Elektronika MK-52 programmable calculator. 

I got it in 1991.

It is a calculator from the MK-61 series, but it has a rewritable ROM. It was very convenient not to have to enter programs by hand.

I also had a БРП/BRP (memory expansion unit), model БРП-4 (BRP-4).

Some ready-made programs were stored in the unit.

You could not write your own programs in it. But you could quickly load these ready-made programs into the calculator and then run them.

With the calculator I learned the practical basics of programming (and they were different from the theory).

Funny thing: the ERROR message can appear during a calculation, but it was read as ЕГГОГ (EGGOG).

Then in 1992, I got an 8-bit Партнер/Partner 01.01 computer (with an i8080 clone). In 1993, a cheap PC-compatible (i8088 clone) 16-bit Поиск/Poisk. In 1994, a 32-bit PC with an AMD 80386SX compatible CPU.

See also related notes:

• Books of my childhood (2023-08-17)
• ПК Партнер 01.01 (2015-11-16)

Image albums:

• PC

DiC & MiC E302C Tripod: Broken twist lock

I use the DiC & MiC E302C carbon tripod a lot. In general, I like it. For me it is a good compromise between compactness, weight, height, and stability.

But a break has happened.

Twist locks consist of two parts: the outer one (which you have to twist) and the inner plastic lock bushing. The bushing must be snapped into the outer part, allowing it to rotate.

One of the twist locks is broken. The lock bushing now does not snap into the outer part.

So when the twist lock is unscrewed, this bushing remains to lock the leg section:

It is possible to pull this section out, but it is very difficult to push it in. This is very uncomfortable.

This is how it should be (a working twist lock):

I don't know how to fix this. I try not to use this level of sections for now.

See also related notes:

• DiC & MiC E302C tripod: Disadvantages (2023-12-17)

Image albums:

• Tripod

Angarsk, snow (September 2004)

Angarsk, 30 September 2004.

Morning:

Evening:

That's the exact sequence.

Pentax Optio 450 (4MP, 1/1.8") @ 7.8mm (37mm equiv.)

Image albums:

• Angarsk

SZ Viewer A1-2023-10-01 (Android)

SZ Viewer (Android) changes:

1. A new experimental tab that contains only temperature values from all known modules.

See also related notes:

• SZ Viewer: общая информация (2014-02-15)

Image albums:

• On-board diagnostics

Anastigmat Victar 50/2.9: My experience [2/2]

(see part 1)

And more examples taken with the Sony a7c (FF, 24MP) and the Anastigmat Victar 50/2.9 lens at f/2.9.

The triplet's traits are visible.

But to fully reveal them, you need to help the lens and reduce the minimum focusing distance.

See also related notes:

• Anastigmat Victar 50/2.9: With close focus (helicoid) adapter [1/2] (2023-10-14)
• Anastigmat Victar 50/2.9: My experience [1/2] (2023-09-29)

Image albums:

• Victar 50/2.9

Anastigmat Victar 50/2.9: My experience [1/2]

All examples were taken with the Sony a7c (FF, 24MP).

The Anastigmat Victar 50/2.9 lens is old (from the 1940s), optically simple (it's an uncoated triplet). Therefore, the photos look vintage. But it's not all that bad, the key is to increase the contrast and choose the right scene to shoot.

Landscapes lack resolution at the edges and corners, even with the aperture closed (f/8-f/11).

But in the center, the resolution is surprisingly good, even at f/2.9:

Vignetting is also low.

But it's better for shooting subjects at f/2.9.

A certain softness is present, but there is also background blur.

With small subjects, the "soap bubbles" of a triplet are present.

But a sufficiently large minimum focusing distance will not allow you to get large "bubbles" in the background.

Triplets are very demanding in terms of optical element alignment. It is possible that this is not the best copy. But the level of photographic quality back then was very different from today (this applies to everything: photographic materials, cameras, lenses).

See part 2.

See also related notes:

• Anastigmat Victar 50/2.9: With close focus (helicoid) adapter [1/2] (2023-10-14)
• Anastigmat Victar 50/2.9: My experience [2/2] (2023-09-30)

Image albums:

• Victar 50/2.9

Google Chrome: "All Bookmarks" button/folder/tab

To remove the "All Bookmarks" button/folder/tab from the Bookmarks toolbar of the Google Chrome browser go to link: chrome://flags/#power-bookmarks-side-panel (copy the link and paste it into a new tab) and disable the "Power bookmarks side panel" feature.

That annoying "All Boorkmarks" thing looked like:

Image albums:

• Internet