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06-19-2015, 12:56 PM   #1
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Using the Pentax AF280T flash with Pentax K Kx

Greetings all,

I need to know if I will be able to use my Pentax AF280T flash on a Pentax K kx digital camera I am considering purchasing. Thanks very much for any help.

tt

06-19-2015, 01:04 PM   #2
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You can use it, but it won't support any automation. I'd instead recommend something like the AF 201FG or a Metz 52 as a starter flash.

Adam
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06-19-2015, 01:38 PM   #3
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QuoteOriginally posted by Adam Quote
You can use it, but it won't support any automation.
Not wanting to contradict you directly, Adam, but I own the AF280T and it supports more automation than one might think. For sure, it does not support P-TTL. It was designed for the true TTL found in various film bodies. What is not well known is that Pentax dSLRs provide partial support for the legacy analog control protocol on the AF280T. The feature support is good enough that I actually prefer my AF280T over my Sigma EF-610 DG Super for most uses. What that means is:
  • The flash's on-board auto-thyristor exposure control works transparently allowing for accurate exposure for both bounce and swivel
  • Flash ready and flash exposure correct will both signal in the viewfinder
  • The camera continues to oblige by supporting the following (dependent on exposure mode):
    • Shutter speed is set automatically to balance against ambient light
    • Aperture is set appropriate for the flash mode and set camera ISO
    • Override of both shutter and aperture are allowed with green button returning settings to base state
  • Full manual operation at two intensities is also available without having to wade through a maze of menus
For a full discussion, see my review of the AF280T:

PENTAX AF 280T reviews - Pentax Camera Accessory Review Database

...at present, the second review on the most recent page.

Since the OP already owns, the AF280T, I would suggest giving it a run on the new camera. At the very least, it can be used quite nicely in X or M mode with using just the on-board sensor without leveraging the body features.


Steve
06-19-2015, 02:34 PM   #4
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Steve has the better answer here. I have used an AF 280T with all of my Pentax DSLR bodies. In my case, I went to it when I found that a couple of my family members were "blinkers" with P-TTL, so at family affairs, if I need flash, it's still pretty brainless to use the 280 in auto thyristor mode. It's a good unit and has served me well over the years.

Scott

06-19-2015, 06:22 PM   #5
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It really exposes for bounce and swivel?

QuoteOriginally posted by stevebrot Quote
What that means is:[LIST][*]The flash's on-board auto-thyristor exposure control works transparently allowing for accurate exposure for both bounce and swivel [*]Flash ready and flash exposure correct will both signal in the viewfinder[*]The camera continues to oblige by supporting the following (dependent on exposure mode):
  • Shutter speed is set automatically to balance against ambient light
  • Aperture is set appropriate for the flash mode and set camera ISO
  • Override of both shutter and aperture are allowed with green button returning settings to base state
06-19-2015, 08:13 PM   #6
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QuoteOriginally posted by Spodeworld Quote
It really exposes for bounce and swivel?
Yes, the flash has its own photocell on the front that may be used in either of two auto modes. It also supports analog protocol TTL as well as two levels of full manual. There are limitations, but for general shooting the results are very consistent and the auto modes work equally well with ALL Pentax compatible lenses. For example, with a K-series or M-series lens mounted, the AF280T operates the same on my K-3 as it would on a ME Super film camera.


Steve
06-22-2015, 02:44 PM   #7
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You mean the Red and Green auto modes, right?

It's not TTL, so how could the thyristor adjust its reading depending on whether you use direct, modified or bounce flash?

QuoteOriginally posted by stevebrot Quote
Yes, the flash has its own photocell on the front that may be used in either of two auto modes. It also supports analog protocol TTL as well as two levels of full manual. There are limitations, but for general shooting the results are very consistent and the auto modes work equally well with ALL Pentax compatible lenses. For example, with a K-series or M-series lens mounted, the AF280T operates the same on my K-3 as it would on a ME Super film camera.


Steve
06-22-2015, 03:30 PM   #8
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QuoteOriginally posted by Spodeworld Quote
You mean the Red and Green auto modes, right?

It's not TTL, so how could the thyristor adjust its reading depending on whether you use direct, modified or bounce flash?
QuoteOriginally posted by stevebrot Quote
Yes, the flash has its own photocell on the front that may be used in either of two auto modes. It also supports analog protocol TTL as well as two levels of full manual. There are limitations, but for general shooting the results are very consistent and the auto modes work equally well with ALL Pentax compatible lenses. For example, with a K-series or M-series lens mounted, the AF280T operates the same on my K-3 as it would on a ME Super film camera.


Steve

Yes, red and green auto modes. In either, it is the front-facing photocell of the the flash that is controlling the amount of light via the thyristor. The flash head can swivel up and down and sideways independent of the lower body of the flash, where the photocell is. The photocell must always be aimed at your subject, while the flash head can be bouncing light off of the ceiling or wall with diffusion or not.

06-22-2015, 03:57 PM   #9
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QuoteOriginally posted by TedH42 Quote
Yes, red and green auto modes. In either, it is the front-facing photocell of the the flash that is controlling the amount of light via the thyristor.
What he said. Think of it as a real time flash meter or TTL flash without the lens in the way. Auto-thyristor flashes are not as common now as they once were, but the tech works quite well and is an option on some modern speedlights. In the current line of Pentax flashes, only the AF540FGZ and AF360FGZ support auto-thyristor control.


Steve

Last edited by stevebrot; 06-22-2015 at 04:06 PM.
06-23-2015, 05:49 AM   #10
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OK. I assume that the reading is valid for when the flash is facing forward, but if it is facing away, the thyristor would not be aware of that and would not compensate for the additional power required when bouncing or modifying the flash.
06-23-2015, 07:14 AM   #11
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QuoteOriginally posted by Spodeworld Quote
OK. I assume that the reading is valid for when the flash is facing forward, but if it is facing away, the thyristor would not be aware of that and would not compensate for the additional power required when bouncing or modifying the flash.
Of course. But the flash head, at the top of the flash unit, points independently of the flash body, which contains the still-forward-facing photocell that controls the thyristor. Pointing the photocell anywhere other than towards the subject makes no sense. The flash head does its bounce thing without forcing the photocell to point away from the subject.

Regardless of where the flash head is pointing, or how the light is modified, the photocell (still aimed at the subject) forces the thyristor-controlled flash tube to keep emitting light until the subject has received enough light to satisfy the photocell that is looking at the light coming from the subject towards the camera (assuming on-camera flash). Then the lens aperture determined by the red or green auto mode will give the "correct" exposure (for a "middle gray" subject).

Note that the flash unit does ALL the "auto" part, while the camera has its aperture manually set to the value read off the back of the flash unit.

If the flash is not on-camera, or if there is significant ambient light, the situation gets more complicated, and the flash unit has no additional smarts to deal with this. That's what TTL works to fix. But the A280-T flash does not do any TTL with our digital cameras. Worked nicely with my film LX.
06-23-2015, 08:14 AM   #12
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i think don't to use.,.,
make give not good result.,.,


06-23-2015, 08:46 AM   #13
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Oh, maybe that's the part I didn't get...that the thyristor is working realtime to determine whether of not the subject has been sufficiently illuminated. I thought it was reading the value prior to the image being captured and determining how much light would be needed.

QuoteOriginally posted by TedH42 Quote
Regardless of where the flash head is pointing, or how the light is modified, the photocell (still aimed at the subject) forces the thyristor-controlled flash tube to keep emitting light until the subject has received enough light to satisfy the photocell that is looking at the light coming from the subject towards the camera (assuming on-camera flash). Then the lens aperture determined by the red or green auto mode will give the "correct" exposure (for a "middle gray" subject).

.
06-23-2015, 09:08 AM - 1 Like   #14
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QuoteOriginally posted by Spodeworld Quote
Oh, maybe that's the part I didn't get...that the thyristor is working realtime to determine whether of not the subject has been sufficiently illuminated. I thought it was reading the value prior to the image being captured and determining how much light would be needed.

Exactly - the realtime measurement of the light as the flash is generating it IS its "auto" functionality.
06-23-2015, 10:47 AM   #15
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Yes, Autothyrister is very good for most shooting situations, but can be less so on occasion for shooting macro especially (the flash sensor is relatively farther away from the sensor plane as you move closer).

Many Canon wedding photographers shoot Auto - even though the newer Canon pre-flash TTL system is far better than the Pentax implementation. The biggest advantage is the lack of preflash delay. However, averaging light and dark areas (as in wedding apparel) often works out better than the supposedly smart metering used in modern TTL design. As long as the flash sensor is directed toward the subject, and your bounce / diffusion is aimed properly, the exposure should be good. In fact, Auto does not get fooled by specular reflection (sequins, etc.) like pTTL; it just isn't all that sensitive.

It does surprise me that so many highly experienced Pentax shooters hang onto their hope that pTTL will be good enough some day. Yes, some strides have been made, but pTTL is inferior to Auto in the vast majority of situations.

Last edited by ScooterMaxi Jim; 06-23-2015 at 10:53 AM.
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