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2023-05-03

Sony a7c: readout speed (video mode)

I measured the sensor readout time of the Sony a7c in photo mode when using Silent Shooting (full electronic shutter). Now it's time to explore the video modes.

The methodology is the same: a fast blinking (500Hz) LED is recorded. One pair of lines (dark line and light line) is 2 ms of the sensor reading.

1. Full-frame width, 4K 25/24 fps [PAL/NTSC]

About 12.4 pairs, 24.8ms.




2. x1.2 crop width, 4K 30 fps [NTSC]

About 8.6 pairs, 17.2ms.




3. Full-frame width, Full HD 25/50/100 fps [PAL]

About 4 pairs, 8ms.




4. Full-frame width, Full HD 24/30/60/120 fps [NTSC]

About 3.6 pairs, 7.2ms




5. APS-C, 4K 25 fps [PAL]

About 7.9 pairs, 15.8ms




6. APS-C, 4K 24/30 fps [NTSC]

About 6.9 pairs, 13.8ms.




7. APS-C, Full HD 25/50/100 fps [PAL]

About 3.9 pairs, 7.8ms.




8. APS-C, Full HD 24/30/60/120 fps [NTSC]

About 3.4 pairs, 6.8ms.




Reading in 4K modes is rather slow.

You can see that Full HD modes do not use the same sensor area as 4K, it skips lines. This causes a lot of aliasing, so I find Full HD on the Sony a7c useless.

The value of sensor readout speed is very important for software stabilization with Gyroflow (at least in 4K). It is necessary to always enable "Rolling shutter correction" and set "Frame readout time".



An inaccurate value or a deactivated correction will not allow to achieve a good stabilization.

Posted by malykh в 00:06 0 comments

2023-05-01

Pentacon 30/3.5 (M42x1)

The only East Germany lens I had was the Carl Zeiss Jena DDR Flektogon 35/2.4. I didn't like it, preferring the Mosler Fotoguard (Tokina) 35/2.8 and the Pentax K 35/3.5. Now I have another one from East Germany. This is the Pentacon 30/3.5 with M42x1 mount.

PENTACON 3.5/30:



German Democratic Republic:



This lens is a later version of the older Meyer-Optik Görlitz Lydith 3.5/30 lens, which is interesting for its simple retro-focus optical design without cemented elements. There are only 5 elements in 5 groups (looks like a retro-focus Ernostar).



The Pentacon has the same optical design 5/5 (source):



Mine is the latest Pentacon 30/3.5 with a green ft. scale (from the 1980s, as far as I know).



Earlier Pentacon versions had a red one.

This is a preset aperture lens. The aperture ring is single, but it's outer part can be slid forward to set the limit of the aperture closing.



It locks at the following positions: f/3.5, f/4, f/4.8 (intermediate), f/5.6, f/6.7 (intermediate), f/8, f/9.5 (intermediate), f/11, f/16, f/22. The aperture ring rotates from f/3.5 to the locked value without clicking.

A 10-blade aperture, but not round in shape.



The filter thread size is 49mm. This lens is quite small.

The minimum focusing distance is about 30-35cm, which is good for a non-modern lens.



I liked this lens. It doesn't provide very good resolution over the entire frame (on the Sony a7c, FF 24MP), but it has other interesting features. And it's an inexpensive lens. Perhaps it is unpopular because of the name (not Meyer-Optik) and the f/3.5 aperture.

By the way, there is a modern remake version called the Meyer-Optik Görlitz Lydith 30/3.5 II, but it's quite expensive.

Posted by malykh в 00:00 0 comments

2023-04-27

Ricoh GR: Dust on the sensor

I really like the Ricoh GR camera (1.5 crop, 16MP), but I admit it has problems.

For example, the dust on the sensor, which appeared and disappeared. And now I see two dust particles that are visible in the image of the sky.

Example of the entire image, f/5.6 (common landscape aperture):



A cropping of these two dust particles from the upper right corner:



Seems like a small thing, but when you see it regularly, it's annoying. I have to remove them programmatically, as I have no desire to disassemble the camera to clean the sensor.

It is especially unfortunate that the problem of dust on the sensor remains with the Ricoh GR III, which attracts new features. The "Dust Removal II" cleaning is of little use.



See also related notes:
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Posted by malykh в 00:05 0 comments

2023-04-25

Sony F35: Digital cinema camera with non-square, non-Bayer pixels (2008)

The Sony F35 is Sony's first digital Super 35 (23.6x13.3 mm, 16:9) video/cinematography camera (2008).



Its special feature is that it uses non-Bayer filters for the pixels of  the CCD sensor. Moreover, the pixels are not square (to maintain the 16:9 aspect ratio of the output video).



The true sensor resolution is 5760 (1920x3) x 2160 (1080x2) pixels (about 12MP total). A group of 6 (3x2) pixels gives one pixel output. Therefore, the video resolution is 1920x1080 (FullHD).

The six sensor pixels (generating one output pixel) contain two sets of three R, G, B pixels. This makes it possible to avoid Bayer interpolation. Full RGB color reconstruction is straightforward.

This was an attempt to compete with 3CCD systems, which use a complex optical system with image decomposition on three monochrome (R, G, B) sensors, but the flange focal distance is too large to use some cinema lenses and the optical quality is not good enough.

This idea of the Sony F35 sensor was not continued.



Image albums:
Posted by malykh в 00:24 0 comments

2023-04-23

Angara, Irkutsk (June 2006)

A transmission tower on a small island in the Angara River, Irkutsk, June 2006.




The Pentax *ist Ds DSLR (1.5 crop, 6MP) with the Pentax A 50/1.7 lens.


Also a black and white photo taken on BW400CN film, 2006.



The Pentax Z-1 SLR with an unknown lens.



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Posted by malykh в 00:08 0 comments

2023-04-21

Mosler Photoguard 35/2.8 and Tokina Wide Angle 35/2.8 (preset)

I still like the rare Mosler Photoguard 35/2.8 (first preset version). That's why I keep looking for information about it.

(on the right)

"Lens made in Japan":



I had heard that it was a Tokina (made by Tokyo Koki), and it can be confirmed.

Tokyo Koki 35mm f/2.8 W. Tokina (Wide Tokina) preset (source):




The Mosler is a copy of this Tokina. Even the big flat screw head on the focus ring is there (I thought it was a repair replacement on my copy only).

The Tokina was also known as the Lucky-Tokina:




The Minetar [Wide Angle]:




The Palinar [Wide Angle] (source):



The Hanimex [Wide Angle]:




The Soligor (source):




The Vemar [Wide Angle] (source):




The Cunor [Wide Angle]:



The Super-Lentar [Wide Angle]:





The PrinzGalaxy:




Similar design and lettering, T-mount, 8 aperture blades f/2.8-22, 49mm filter thread.

But I can't find the optical design of this lens. Supposedly there are 6 elements. Maybe the design is similar to, for example, the Konica Hexanon 35mm f/2.8 (preset). 6 elements in 5 groups (a descendant of the Angénieux retrofocus):



Or it could be completely different.

Posted by malykh в 00:00 0 comments

2023-04-19

A town in the taiga (Angarsk, 1957): higher resolution version

I showed the article "A town in the taiga" about Angarsk. It is an electronic version that can be found on the Internet. But the quality of the image is rather poor.

I found and bought the paper version of this magazine (from 1957).



And here is a scan in better quality:



And the photo by itself.





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Posted by malykh в 00:07 0 comments

2023-04-17

Sony a7c: My menu and Fn settings

Updated 2025-05-23

The main menu (called by pressing the Menu button) of the Sony a7c camera is quite difficult to understand and use. There are illogical organization and terms that are not always clear.

But this problem is solved by setting up the "My Menu" section of the main menu and the menu called by the Fn button. This is very convenient.

I use four of my menus in total:

1. General

Cleaning Mode
Format - It is easier to format the SD card than to remove all media using the main menu.
APS-C/Super 35mm
Face/Eye AF Set.
Live View Display - Setting Effect ON/OFF

2. Connectivity

Airplane Mode - It is faster to control the airplane mode than to toggle FTP transfer state directly.
FTP Transfer Func.
Bluetooth Settings - To use with the Bluetooth remote control.
Ctrl w/ Smartphone - Control with the mobile application (I don't use it now)

3. Display

Peaking Setting
Zebra Setting
Monitor Brightness
Display Quality
Viewfinder Bright.
Photo: Finder Frame Rate


4. Video

Video: File Format
Video: Record Setting
NTSC/PAL Selector - To switch between 60/30/24 and 50/25 fps
Volume Settings
Gamma Disp. Assist - Useful when using a Picture Profile
Video: USB Streaming


And my Function (Fn) Menu settings:

1. Photo

Drive Mode
Focus Mode
Focus Area
Subject Detection
ISO
Metering Mode

White Balance
ISO Auto Min. Shutter Speed
SteadyShot Focal Length
SteadyShot
Photo: Silent Shooting
Shoot Mode


2. Video

Audio Record Level
(as Photo) Focus Mode
(as Photo) Focus Area
Picture Profile - it is a powerful tool to control Gamma and Color Mode for video recoding.
(as Photo) ISO
(as Photo) Metering Mode

(as Photo) White Balance
Steady Shot Adjust
(as Photo) SteadyShot Focal Length
(as Photo) SteadyShot
Touch Operation
(as Photo) Shoot Mode


I also defined the Fn button to start FTP transfer in the view mode.
Posted by malykh в 00:14 0 comments

2023-04-15

Industar-61L/Z-MC 50/2.8 and Pentax M 50/4 Macro

Индустар-61Л/З-MC (Industar-61L/Z-MC) 50/2.8:



This is the first lens I ever bought. Before that, I got lenses for free.

I used the lens quite often on my Pentax *ist Ds. In fact, it was the main lens on this DSLR for the first time.

It's much more usable than the Индустар-50/50-2 (Industar-50/50-2), but I can't call the image quality very good. Although this copy is good.

Now I use the Pentax K 50/4 Macro (also Tessar type, 4 elements in 3 groups) instead.



The Pentax M 50/4 Macro is better both optically and mechanically, it gives more magnification (up to 1:2).

(at the minimum focusing distance)

And the difference between f/2.8 and f/4 doesn't matter for the task at hand.

Posted by malykh в 00:08 0 comments
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