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08-04-2020, 11:30 PM   #106
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QuoteOriginally posted by termy Quote
maybe try 1/16 of the flash output?
tried that, didn't worked...

08-05-2020, 02:48 AM   #107
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QuoteOriginally posted by termy Quote
maybe try 1/16 of the flash output?
I don't have one of these, so I'm of limited help, but isn't this unit meant to work with TTL and P-TTL? It does seem from previous posts that many have a fault of working only at full output, even when switched to a reduced manual mode which should not involve the camera circuitry. It seems to be either a type-fault in these units, or an incompatibility with some camera models. I advise Weevil to try and get his money back, IDK what he paid but these things are usually silly-expensive.

Out of interest, to test whether the fractional manual modes work do work at reduced output I would take some test shots in a darkened room with the camera on Bulb for each shot, and firing the flash at the subject with the unit off the camera and triggered manually. I can't find a decent photo of the unit's back but I presume it does have a test button to do this.

I believe this unit has no AUTO mode (ie controlled by a sensor in the unit body), but units in AUTO mode do often expose badly for close-ups because the sensor's angle of view is then largely outside the subject area.

I do a lot of ring flash macro work using a cheap and cheerful but perfectly satisfactory Cobra Macroflash Cobra Macrofalsh reviews - Pentax Camera Accessory Review Database used on manual (I do the sums). Ebay has loads for around £15 (sold under various names - Vivitar, Starblitz etc). I has a GN of only 5 which is all you need for macro, especially as you can wind up the ISO on digital cameras if you need to. TBH, a GN of 16 is over the top for macro work and is probably meant for people who expect also to use the unit for general indoor work. But direct ring flash does not make for good portraits unless you are doing prison mug-shots.

Last edited by Lord Lucan; 08-05-2020 at 02:53 AM. Reason: Tpyo
08-05-2020, 08:36 AM - 1 Like   #108
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QuoteOriginally posted by Weevil Quote
Does anyone can tell me what is the exact issue in a nut shell ? (sorry, when I read many technical explanations, I am getting confused)
QuoteOriginally posted by Weevil Quote
has the issue been recognized by Ricoh/Pentax finally?
I will start with the second matter first. Current Ricoh/Pentax documentation indicates that while P-TTL will work with Pentax-A series lenses, flash control is not consistent with other than AF lenses.

One may ask, "What is the difference between KA and KAF (and higher)?" A major difference is the presence of an additional (data) contact on the mount that is used for sending information about the lens and its current status. While the full extent of information shared is unknown, the makernotes portion of the EXIF has a location that apparently includes a rough estimate of distance based on the focus ring position. Note that while Irix lenses are KA2 and have the data contact, I am not sure it is fully known what information the various those lenses share.

OK, so why would that be important? Taking a step back, there are a few small experiments that one can do. While the results are more obvious with a higher powered flash, even the built-in P-TTL flash will do. Here is the first experiment:

Preflash with AF Lens
  1. Set the drive mode to 2 second delay (3 second on some bodies). This allows us to see the preflash separate from the main flash.
  2. With an AF prime on the camera, put the focus ring at infinity and AF/MF switch to to MF.
  3. Release the shutter and note the brightness of the preflash. (Zooms will work, but a prime is easier to handle.)
  4. Repeat with the focus ring at minimum focus distance.
The preflash should be noticeably brighter at infinity than at close focus. The second test is similar:

Preflash with A-series lens:
  1. Using a KA mount lens (Pentax-A or similar third-party), repeat the experiment above. The preflash intensity should be strong and the same at both infinity and close focus.
  2. Do an in-focus exposure of a subject at about five meters with the lens at maximum aperture and ISO 400. The flash exposure should accurate for most P-TTL flashes for those settings.
  3. Repeat the above for a subject at one meter distance. I would expect gross overexposure.
  4. Repeat again and note that the main flash intensity at one meter is as bright or brighter than that at five meters
Speculation is that the overly-bright preflash at one meter results in an out-of-range light meter response (an error state) with resulting P-TTL "fail-over" behavior of discharging the main flash at full intensity with no obvious error messaging. I know that sounds brain-dead, but short of providing a cryptic error message, what else would one suggest?

What are the workarounds for P-TTL with non-AF lenses? Full manual operation when doing close-up work is the most obvious. ND filter on the flash is another option, one that I have not tried. Ditto for routinely using narrow apertures and low ISO for close-up flash work. From all reports, cursing does no good with similar results to be expected if the curses are in a letter to Ricoh/Pentax. BTW...I have no idea how regular TTL (both analog and digital protocols) flash on older cameras such as the *ist D handles this case.


Steve

Last edited by stevebrot; 08-05-2020 at 08:50 AM.
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