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Forum: Digital Processing, Software, and Printing 3 Days Ago  
The Darktable Users Coterie
Posted By kaseki
Replies: 148
Views: 11,927
Today I opened my Flatpak installation of Darktable to convert a jpg into a rotated hard copy. For the first time in my intermittent recent openings, Flatpak pulled the 3.0.0 version instead of the 2.6.3 version. From this I conclude that a version 3 Flatpak configuration has finally been built and put into the Flatpak repository (or whatever it is called). It does convert some stuff, but the message wasn't too clear about what.
Forum: Flashes, Lighting, and Studio 6 Days Ago  
AF-360FGZII contrast control operation
Posted By kaseki
Replies: 14
Views: 472
I have an AF{560/360}FGZ II operating manual, but no physical FGZ IIs. The manual does not show a 5P connector on the flash. So any attempt to cable connect would require using F hot shoe connectors with 5P cables. See pages 55 and 61 of the operating manual. The text on page 55 suggests this configuration is quite limited in capability, but I have no experience with it.

With old school TTL using FTZ flashes, a number of flashes can be hooked in parallel using 5P cables; all will be quenched at the same time when the in-camera TTL measurement says "enough." Contrast will be whatever the flash configuration will accomplish, given distance, aiming, modifiers, etc. I remain unclear whether daisy-chained or home-run multi flash configurations of FGZ (not II) in TTL mode can operate, as this series of flashes is digitally controlled.
Forum: Pentax Medium Format 02-13-2020, 07:29 AM  
Post your medium format photos!
Posted By kaseki
Replies: 14,108
Views: 2,392,207
90mm, 645Z, unprocessed camera jpg. Comparing my monitor's view of this preview image taken about an hour ago to the view outside now suggests that a bit of white balance increase and a tad of bluing might be called for, although this may only be due to a higher sun angle behind the clouds. It was fairly gray outside when this photo was taken. [EXIF time is EDST; forgot to fix it.]
Forum: Digital Processing, Software, and Printing 02-11-2020, 12:08 PM  
Adobe RGB controversial?
Posted By kaseki
Replies: 61
Views: 1,871
I can report that the PEF files from my Z are in the 55 MB to 65 MB range. I have only begun to mess with Darktable, and haven't kept many experimental results. I found one TIFF that is 293.4 MB, but I don't recall what parameters I set on the conversion. I assume that either it was a simpler scene than the 400 MB K1 example, or I unintentionally used some parameter that reduced detail in some respect.
Forum: Digital Processing, Software, and Printing 02-10-2020, 09:34 AM  
Monitor Calibration Tool Recommendation
Posted By kaseki
Replies: 36
Views: 1,107
Bruce:

Let me try this analogy as an answer to your question about self calibrating to make the image look right. You might be able to selectively adjust RGB to make an image look like you think it should, or even an electronic version of an x-rite color checker Passport look the same as one in the hand illuminated at the correct color temperature, but when you were done it is unlikely that a directed RGB = {255, 255, 255} input would have the correct luminosity *(e.g., 80 nits), and it is unlikely that the "gamma" would be the desired 2.2 over the brightness range of dimmer-than-maximum images or image parts. For these corrections to be made, a matrix of values has to be constructed from a matrix of measurements such that RGB is properly tweaked over the gray-scale range of your monitor. This is a fairly recursive process to do manually, and even an automated system has to solve a set of simultaneous equations to obtain a proper result. (I assume that the algorithm used is akin to the one used in Excel's Solve program, but perhaps other approaches have been adopted.) Thus, manually "improving" a factory calibrated monitor that has aged a bit may well be counterproductive.

I should add that the calibration programs attempt to also minimize the error in display of intermediate colors because display generated red, green and blue are unlikely to exactly match the eye's photosensitivity curves designated by those colors.

kas
Forum: Pentax Medium Format 02-07-2020, 07:25 AM  
Post your medium format photos!
Posted By kaseki
Replies: 14,108
Views: 2,392,207
Visited a south-central New Hampshire (Amherst) winery named LaBelle's for an early dinner. Brought the 645z backpack in case there was a nice sunset. Ended up with an interesting sunset and a lot of winery photos, a very few of which are embedded below in case someone wants to visit.

Barrels and tanks are part of a much more extensive cellar. The main floor is mostly restaurant space.

The sunset photos were low in color, but had a very interesting cloud formation that rapidly grew over the period from 4:30 PM to 5 PM EST. Later that night there was a modest snowstorm, leaving 3 inches at my house.

The following are jpgs from the camera, without further processing. EXIF time seems to be Eastern Daylight Savings Time, so subtract an hour for EST. Shots are handheld, but in some cases the hand was supported. ISO was generally set to keep exposure times short enough that resolution wasn't degraded by any lack of steadiness on my part. Outside temperature was about 35F.
Forum: Flashes, Lighting, and Studio 02-06-2020, 05:29 PM  
CT-16 flash trigger and Shanny SN600FGZ - not working together
Posted By kaseki
Replies: 11
Views: 414
I'm sure you're thinking what I am thinking, if 2.9 kΩ is sufficient to fire the Shanny, then surely the effective collector-emitter impedance of your circuit will be lower than 2.9 kΩ. I can only guess that the transistor you are using is not going sufficiently "ohmic" when the base is pulled down, pulling down the emitter-collector voltage. Even the emitter to base path of ~ 0.6V +100Ω may be insufficient for the Shanny when the CT-16 voltage is not going to zero as one would expect of a good trigger, but only down to "about 1.7 - 1.8V." One would need a V-I vs Vbe transistor curve set for your particular transistor to see just what is happening, but I think that a means to drive the Shanny trigger voltage well below the voltage that the CT-16 is dropping to is needed.

I guess I should ask: When the 2.9kΩ resistor is used to trigger the Shanny, what value does the voltage on the Shanny trigger pin fall to?

An insulated gate FET (usually MOSFET) should be ohmic when its gate voltage is sufficient (positive or negative). The question is whether it should be p-channel or n-channel, enhancement mode or depletion mode, and whether one of these configurations will work without a bias circuit. My present guess is that a p-channel enhancement mode device, with source connected where your transistor's emitter is connected, and gate connected as the base is in your circuit, would have the functionally correct polarities. Whether the CT-16 voltage drop at triggering is sufficient for a particular FET specimen remains an unknown to me. Analysis of a particular device would be needed to see if 2.9 kΩ is achieved in the ohmic region assuming the voltage behavior is suitable. Ultimately, the CT-16's poor voltage drop on triggering is both the issue and a limitation on doing something about it with minimal components.

Caution: MOSFET hacking requires full ESD regalia unless the device has internal protection.
Forum: Flashes, Lighting, and Studio 02-04-2020, 08:48 PM  
CT-16 flash trigger and Shanny SN600FGZ - not working together
Posted By kaseki
Replies: 11
Views: 414
While this looks like it should work at first glance, there are some needed data that would help. With the circuit in place, what is the voltage on the Shanny trigger pin before and during the trigger; what is the voltage on the output of the CT-16 for those two conditions, and for extra credit, what is the voltage behavior on the transistor base, referenced to the shoe grounds.

The act of trying to short the Shanny might be countered by the transistor not conducting adequately when the voltage drops. One needs to look at the "triode" like behavior of a transistor, when the collector to emitter voltage gets low, to see what happens to its apparent resistance.

It may be necessary to use an FET (I'd have to resurrect decades-old aged-out knowledge to say which sex of FET without some study) to drop impedance relatively independent of the drain to source voltage.

Otherwise, a more complex transistor circuit with a battery seems more certain. I haven't given this much thought yet though.
Forum: Flashes, Lighting, and Studio 02-03-2020, 01:05 PM  
CT-16 flash trigger and Shanny SN600FGZ - not working together
Posted By kaseki
Replies: 11
Views: 414
You are welcome. I tried to think of a simple scheme using a pair of those photocell cubes to increase pull down, but nothing that avoided tearing into one came to mind. Good luck.

Addendum: There exists a Pentax F connector device (I think this is the "hot shoe adapter F") that has a hot shoe on the top, and inverse hot shoe (flash body connector) on the bottom, and a 5P cable receptacle on the side. It could be internally modified, I think, because it appears to be held together with screws. The bad news is that these are very expensive, $65. However, there may be a cheaper device of this general form comprising the top and bottom sides' hot shoe features with only center pins and commons, and a sync tap.

Of particular note is this HAMA HA-6950 beauty found at B&H for $23. It has a top shoe and a bottom camera shoe fitting and a pair of PC sockets. These are not connected. You have to connect the one PC socket to the other to operate the top shoe from a camera (or remote) on the bottom. This configuration suggests that a transistor circuit could be inserted into the PC connector path so long as one had some PC cables to play with.

https://www.bhphotovideo.com/c/product/89977-REG/Hama_HA_6950_Universal_Flas....html/overview
Forum: Flashes, Lighting, and Studio 02-01-2020, 08:55 PM  
CT-16 flash trigger and Shanny SN600FGZ - not working together
Posted By kaseki
Replies: 11
Views: 414
If I understand correctly, it looks like the CT-16 doesn't have low enough trigger-ON impedance to pull the trigger pin low enough. Insufficient impedance could be remedied by an intermediate transistor module that one built, but that would be a pain and perhaps not worth the effort depending on alternative approaches.
Forum: Pentax Medium Format 02-01-2020, 12:04 PM  
Pentax 67 focusing screen
Posted By kaseki
Replies: 7
Views: 440
FWIW, my RollieCord mfg. ca. 1937 uses a matte focusing screen that is one-piece. The matte is facing down and the smooth glass is facing up. I am unclear why there would be a plain glass layer as it would just add more specular reflections unless very well AR coated. The 645 uses a one piece focusing screen.
Forum: Flashes, Lighting, and Studio 01-28-2020, 08:22 PM  
New Ricoh griii and Pentax 200fg flash
Posted By kaseki
Replies: 13
Views: 608
Thanks yet again.

According to page 61 of the AF-540FGZ Operating Manual, when used with the 645N the result is TTL. The 645N is a film camera, and presumably doesn't qualify as digital although it is clearly doing digital stuff in order to display what it does. To confirm what is going on, I think I could take my 645N and AF-540FGZ, connect them together by a 5P cable, and use another cable as a split-out where I could monitor the mode pin with a 'scope. This would likely require at least 3-arms to execute unless I built some kind of hot shoe to flying leads adapter. If I think of a scheme that is not more difficult than my curiosity is worth, I'll try it out.
Forum: Flashes, Lighting, and Studio 01-28-2020, 12:20 PM  
New Ricoh griii and Pentax 200fg flash
Posted By kaseki
Replies: 13
Views: 608
Thank you! Interesting and clarifying.

However, since the whole object of TTL is to measure light at the film plane by inference from the film reflection to a TTL detector system in the camera and to stop the flash when enough energy has been detected, the control of the flash has to be dynamic. I can hardly believe that the quench command itself is digital. One has to operate in the microseconds or tens of microseconds regime to get the net illumination of the film plane into the desired exposure region. Your description doesn't explicitly preclude use of the mode pin for quenching even though all other flash actions and reactions might well be communicated through the data pin.

So, Steve, are you sure that the quench is performed via the data pin, or did I misunderstand you and you really intend that digital TTL just means more camera-flash integration and that the mode pin is still used?
Forum: Pentax Medium Format 01-28-2020, 11:59 AM  
Pentax 645N speed dial replacement
Posted By kaseki
Replies: 13
Views: 557
Tune in next season for our thrilling conclusion...
Forum: Pentax Medium Format 01-28-2020, 11:58 AM  
Post your medium format photos!
Posted By kaseki
Replies: 14,108
Views: 2,392,207
Nice!!
Forum: Flashes, Lighting, and Studio 01-27-2020, 05:59 PM  
New Ricoh griii and Pentax 200fg flash
Posted By kaseki
Replies: 13
Views: 608
I'm not sure what you mean by digital protocol for TTL, but I am hoping you will expand my knowledge. My present understanding is that in TTL mode, the camera initiates the flash (by pulling down (electrically) the center contact) and then quenches the flash (by back pulsing the SCR gate using another terminal) when the camera detects sufficient light has reflected from the film plane. I would think of this as an analog protocol. It is the way TTL worked as far back (for me) as the Nikon FG. Perhaps there is also a digital signal available for communication, but I don't expect it to be part of the TTL action. It could, of course, set some parameters such as the flash beamwidth if the capability were there.
Forum: Flashes, Lighting, and Studio 01-27-2020, 05:03 AM  
AF Assist/Modelling Light Strategy
Posted By kaseki
Replies: 42
Views: 1,350
All of the [modern] speedlights I have (500FTZ, 540FGZ, and Cactus RF60X) have red filters in front of their AF illuminator emitters. Perhaps a barely-out-of-the-infrared filtered tungsten modeling light, or deep red LED emitters, would allow AF to work in the near dark without adding much background to the recorded image. I have to assume that the speedlights are filtered for some reason, and I'm guessing here that you might be able to take advantage of it.
Forum: Flashes, Lighting, and Studio 01-27-2020, 04:39 AM  
New Ricoh griii and Pentax 200fg flash
Posted By kaseki
Replies: 13
Views: 608
Suggest an internet search and downloading from one of the Pentax guide sources an AF-200FG user manual and determining whether it supports P-TTL or only TTL.
Forum: Pentax Medium Format 01-25-2020, 09:10 AM  
Telescope adapter for 645D
Posted By kaseki
Replies: 12
Views: 1,435
One thing I neglected to include commenting on is curvature of field. If the telescope image field is only flat enough for 35mm, or worse, only for a 7-mm eyepiece, the image on a ~50-mm width focal plane sensor may only be useful near the center anyway. In that case, a 35 mm to MF adapter may be a practical limit.

Also, it now occurs to me that given the objective's f/no, to get a ray bundle that is fairly big, one has to choke up on the bat, so to speak, and move the "eyepiece" optics closer to the objective. This greatly reduces the magnification. I think this is true even if a pile of glass moves this field diameter behind the telescope without actually physically closing the distance to the objective. The limitations imposed by the Lagrange Invariant are ever present.
Forum: Flashes, Lighting, and Studio 01-24-2020, 05:31 PM  
flash trigger voltage question
Posted By kaseki
Replies: 7
Views: 283
With one cabled flash and the internal flash, I agree. That configuration seems to be supported. With multiple daisy-chained or home-run wired flashes tied via 5P cables to the single hot shoe, your examples of communication conflicts are certainly a concern. As I have a bunch of R60X Cacti and a V6II to control them, my urge to load up on AF-540FTZ units to experiment with is very weak.
Forum: Flashes, Lighting, and Studio 01-24-2020, 12:31 PM  
flash trigger voltage question
Posted By kaseki
Replies: 7
Views: 283
Using a 645N and four AF-500FTZ wired in parallel using 5P cabling, various F devices, and the fact that the 5P receptacles on the flashes are also wired directly to the flashes' hot shoes, I could get all four flashes to operate together and demonstrate that old type TTL functioned correctly. I do not know the limit of number of flashes that would behave with this scheme.

I only have one AF-540FGZ so I can't demonstrate this with the 645Z. But I would guess that 5P cabling is still effective for multiple flashes in parallel in TTL mode, and perhaps if two or more flashes were used in P-TTL mode with cables making them effectively parallel, the calculated flash power from the received combined pre-flash would end up equalized between flashes but would result in a subject irradiance that was inversely proportional to the squares of their respective ranges. This is what happens with the pre-flash, so maybe it would all work out. Note that the AF-540FGZ manual does not address using multiple external flashes attached by 5P cables; it only addresses a single remote flash with cable or wireless slave flashes. There is a risk that paralleling the P-TTL communication channels via the 5P cables would sabotage communications. The FGZ is designed for optical communications when multiple flashes are to be used. Perhaps if whatever scheme Pentax uses for optical comms between multiple flashes is inherent in the electrical communications to separate messages, parallel P-TTL might work.

I believe that the FGZ II has dispensed with the 5P and HV connections. So a somewhat different F-connector layout would have to be used to trigger multiple flashes purely through their hot shoes. Whether joint P-TTL would be possible is beyond my predictive ability, but unless I knew that multiple cable P-TTL was accommodated by pre-planned sophisticated communication timing, I would not expect it to work.
Forum: Pentax Medium Format 01-24-2020, 10:55 AM  
Telescope adapter for 645D
Posted By kaseki
Replies: 12
Views: 1,435
OK, my thoughts are based on fundamentals for whatever they are worth. Note that I haven't taken the time to investigate this particular telescope, so my thoughts are generalities.

First, we must distinguish 'telescope' from 'telescopic.' A telescope, whether Galilean or Catadioptric or whatever, converts ray angles such that incoming parallel rays exit parallel, and parallel ray bundles differing in objective (primary lens) entry angle emerge from the secondary lens group (eyepiece) at some multiple of that angle called the magnification. Magnification equals the ratio of the primary to secondary focal lengths. Astronomical telescopes for private viewing have exit apertures near the nighttime pupil size. It is the human eye's lens that focuses the ray bundles down onto the eye's focal plane: the retina (and in particular, the fovea).

So what is desired is to take a telescope that has both primary and secondary lenses for viewing, and optically mate the secondary to a camera lens that has a field of view equal to that which the secondary has (equals what the primary has times magnification), and which provides an aperture at least equal to the size of the image bundle leaving the telescope secondary. This camera lens may be telescopic in glass design.

All of this ignores how such a pair of assemblies -- camera with lens and telescope -- can be rigidly mounted. Hauling an optical bench with mounting fixtures into the field seems undesirable. Yet some type of mount is needed that keeps them aligned.

The approach used for professional astronomical observation dispenses with both telescope eyepiece and camera lens and focuses the telescope objective onto the camera focal plane (usually film plates or giant imaging arrays). This approach, when applied to devices such as Celestrons and their ilk, requires that the objective focus point be beyond any structure that would mount an eyepiece and far enough back to get to the 645 focal plane (film plane or imaging array plane) if the camera abuts the telescope structure. Whether the entire focal plane is filled depends on blockage and the effective field angle of the telescope given its optical design.

If a telescope is designed to be convenient for 35mm photography, it might lack the features needed for MF focal plane imaging. One can imagine potentially using an optical device that re-images one focus to another, such as a macro lens, or a reversed macro lens. Available f/no would have to equal or be lower in value than the telescope primary's f/no. Perhaps the 1.4X teleconverter could be used for focus extension and image plane magnification.
Forum: Flashes, Lighting, and Studio 01-21-2020, 10:55 AM  
AF Assist/Modelling Light Strategy
Posted By kaseki
Replies: 42
Views: 1,350
Does the phrase "guest posed shots" preclude having a line on the floor that guests stand on that you have manually focused for using a modeling light that is then left off? Would this fail due to limited depth of field and a desire for perfect face focus?
Forum: Pentax Medium Format 01-18-2020, 04:32 PM  
What is the state of Pentax MF??
Posted By kaseki
Replies: 31
Views: 2,392
Surely, some portion of the use cases that would support a sub 25 mm could be effected by stitching, whether stitching multiple images output from the Z sensor, or from scanned film images.

---------- Post added 18th Jan 2020 at 18:57 ----------

Some further contemplation of this quest reminds me that the Holy Grail of two-color IR threat warning sensors is to have fields of view exceeding 90 degrees, telecentric focusing on a flat field, fractional pixel chromatic aberration, high resolution, low f/#, etc., including low cost (in military wallet space). And for threat warning, the last piece of glass can be practically on top of the focal plane because there is no mirror volume. I fear that the large back focus required for the 645 would require something that looks like the Kiev Arsenal 30mm fisheye on steroids -- a giant lens assembly with a small effective aperture.

And hardly anyone would pay for it. Do I correctly vaguely remember that Ken Rockwell a few years ago put up for sale a massive lens of this type for 35mm at an eye-watering price?
Forum: Pentax Medium Format 01-17-2020, 12:33 PM  
Post your medium format photos!
Posted By kaseki
Replies: 14,108
Views: 2,392,207
Looks good on my QHD BenQ in sRGB.
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