Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
06-10-2010, 03:21 PM   #1
Junior Member




Join Date: Aug 2007
Location: Portugal
Posts: 37
Flash - how to know if it works in pTTL/auto with my K10d?

Hi.


I have just bought a second hand Centon FG105D flash, which is the same as the Promaster FTD7000M and the Quantaray PZ-1 DSZ.


I bought it mainly to be used as a slave flash, but I also wanted to use it in auto mode in my Pentax K10d. The specifications state that it's only TTL (not pTTL) compatible, but I read two threads in other forums where some persons said it worked in pTTL with the k10d.


The flash has various modes - TTL, manual, multiple (for multriple flash exposures) and slave. It seems it doesn't have a auto/thyristor mode.


I tried it in Green, P, Av, Sv and Manual modes, and the flash didn't seem to be working in pTTL mode in any of them, except for the Green mode (which says the flash is working in A/auto mode), where the flash didn't yeld over-exposed images like in the other modes. Unfortunately, the Green mode is extremely limited, and I wanted to use it with the largest aperture and a shutter speed of 1/125 or 1/180 (it's for portrait/event work).


What's strange is that the flash seems to be communicating with the camera, because it automatically adjust the flash zoom when I change the zoom in the lens, and it also changes the estimated flash range in the flash lcd.

When I use it in manual, Av or Sv, if I keep all variables constant and change the ISO, images will be more overexposed as I increase the ISO, which means, I guess, that it's not working in pTTL mode.

I have very little experience with flashes, so how can I know if this flash will work in pTTL or auto mode?


I'm looking forward for your replies.

Best regards

06-10-2010, 03:37 PM   #2
Pentaxian




Join Date: Feb 2009
Location: Alameda, CA
Posts: 3,206
I don't know about this flash.

But here's an easy way to see if the flash is working in p-TTL mode: set the camera to 2 sec delay. The rest of the settings are whatever that you think are p-TTL mode.

Hit the shutter release. If the flash works in p-TTL mode, these events will happen in sequence: (1) a weak flash strobe, (2) mirror flipping up, (3) 2 sec later, the shutter release and the main flash strobe.

If the flash does not work in p-TTL mode, (1) does not happen.
06-10-2010, 04:04 PM   #3
Junior Member




Join Date: Aug 2007
Location: Portugal
Posts: 37
Original Poster
QuoteOriginally posted by SOldBear Quote
I don't know about this flash.

But here's an easy way to see if the flash is working in p-TTL mode: set the camera to 2 sec delay. The rest of the settings are whatever that you think are p-TTL mode.

Hit the shutter release. If the flash works in p-TTL mode, these events will happen in sequence: (1) a weak flash strobe, (2) mirror flipping up, (3) 2 sec later, the shutter release and the main flash strobe.

If the flash does not work in p-TTL mode, (1) does not happen.



I have tested the flash a bit more and I get the following:


- When using 2 second timer delay - I don't get the pTTL pre-flash, so I guess this isn't pTTL

- When using Av mode - keeping the ISO constant - the more I close the aperture, the darker the image gets --> the flash should be firing with the same power every time


- When using Manual mode - keeping the ISO constant - keeping the aperture constant - changing the shutter speed - I always get the SAME exposure --> the flash is adjusting it's output power according to the shutter speed?
06-10-2010, 04:22 PM   #4
Pentaxian




Join Date: Feb 2009
Location: Alameda, CA
Posts: 3,206
1. - When using 2 second timer delay - I don't get the pTTL pre-flash, so I guess this isn't pTTL

OK. No pre-flash -> not p-TTL.

The flash has no auto/thyristor mode.

So the flash always fires 1 strobe at full power.

2. - When using Av mode - keeping the ISO constant - the more I close the aperture, the darker the image gets --> the flash should be firing with the same power every time

Assuming the ambient light does not contribute significantly to the exposure, this confirms that the flash always fires at the same level of power: the smaller the aperture, the darker the image.

3.- When using Manual mode - keeping the ISO constant - keeping the aperture constant - changing the shutter speed - I always get the SAME exposure --> the flash is adjusting it's output power according to the shutter speed?

You can't conclude that the flash is adjusting its (BTW, not "it's") output power according to the shutter speed (in fact, none of the current flashes does that). The output of the flash remains constant. The exposure remains the same because the duration of the strobe is shorter than the time the shutter is open, and the ambient light is not significant.

06-10-2010, 05:12 PM   #5
Junior Member




Join Date: Aug 2007
Location: Portugal
Posts: 37
Original Poster
QuoteOriginally posted by SOldBear Quote
1. - When using 2 second timer delay - I don't get the pTTL pre-flash, so I guess this isn't pTTL

OK. No pre-flash -> not p-TTL.

The flash has no auto/thyristor mode.

So the flash always fires 1 strobe at full power.

2. - When using Av mode - keeping the ISO constant - the more I close the aperture, the darker the image gets --> the flash should be firing with the same power every time

Assuming the ambient light does not contribute significantly to the exposure, this confirms that the flash always fires at the same level of power: the smaller the aperture, the darker the image.

3.- When using Manual mode - keeping the ISO constant - keeping the aperture constant - changing the shutter speed - I always get the SAME exposure --> the flash is adjusting it's output power according to the shutter speed?

You can't conclude that the flash is adjusting its (BTW, not "it's") output power according to the shutter speed (in fact, none of the current flashes does that). The output of the flash remains constant. The exposure remains the same because the duration of the strobe is shorter than the time the shutter is open, and the ambient light is not significant.

The classical "it's" and "its" mistake... I know the difference, but every now and then I make the mistake. I'm not a native english speaker, but still there's no forgiveness! :-)


As to the flash, I'm sadly reaching the conclusion that it isn't pTTL, and that it's always firing at full power.


Is there any other kind of test I should do, or option to select in my k10d, that might circumvent this, and make it work in auto or "partial auto" mode?


Considering it will only work in manual, and considering I'll mainly use it in bounce mode, for an indoor event (with only a few shots outdoors), do you think it's possible to achieve good results? I've been doing some testing at home, and with full or 1/2 power in bounce mode, camera in manual with f4.0 and shutter 1/180, I'm getting proper exposures.
06-11-2010, 03:48 AM   #6
Veteran Member




Join Date: Sep 2006
Location: WV
Posts: 1,495
Shutter speed will affect how much ambient light is contained in the exposure but will have no impact on the amount of flash light in the exposure. Flash duration is far shorter than shutter speed.

If the flash always fires at full power, the only way to control the flash exposure that I know of is with aperture and iso. But it seems odd the flash would only fire at full power. If you don't have a manual for it, you might want to search for one online. Also, here's a link to a review of the promaster ftd7000m that might give you some insight.

Promaster FTD 7000M mini review: Pentax SLR Talk Forum: Digital Photography Review
06-11-2010, 06:26 AM   #7
Junior Member




Join Date: Aug 2007
Location: Portugal
Posts: 37
Original Poster
The only thing I don't understand is, considering that the flash isn't communicating with the camera due to the absence of pTTL, then why is the autozoom function and flash range working, when I change camera settings?
06-15-2010, 06:41 AM   #8
Pentaxian
noblepa's Avatar

Join Date: Sep 2007
Location: Bay Village, Ohio USA
Posts: 1,122
You can download the instruction manual from Promaster's website:

http://www.promaster.com/InstructionBooks/FTD7000M_Electronic_Flash.pdf

Are you sure that the unit you bought is dedicated for Pentax cameras? It is/was available for Nikon and Canon, as well.

If it is a Pentax-specific unit, I"m not surprised that the autozoom function works. AFAIK, that part of the communications protocol between the camera and flash is the same, whether its TTL or pTTL. Its just that your camera can't use the TTL subset of the protocol and your flash doesn't understand the pTTL subset.

Its kind of like someone who only knows fifty words of French. He/she can communicate some things with a French-only speaker, but not other things.

05-01-2011, 01:36 PM   #9
Pentaxian




Join Date: Feb 2009
Location: Alameda, CA
Posts: 3,206
QuoteOriginally posted by noblepa Quote
Its kind of like someone who only knows fifty words of French. He/she can communicate some things with a French-only speaker, but not other things.
I don't think we've met. How do you know me? BTW, I'm a "he."
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
av, change, flash, images, iso, lighting, mode, photo studio, pttl, strobist, sv, ttl
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Best Non-PTTL flash for K10D les9596 Flashes, Lighting, and Studio 11 02-02-2009 06:36 PM
PTTL flash question netuser Photographic Technique 4 01-15-2009 10:55 PM
For Sale - Sold: FA 77 1.8, 24mm 1.8, Tam 28-75mm, DA50-200, K10D, K100D, PTTL Flash alinla Sold Items 23 11-16-2008 12:57 PM
K10D Auto ISO now works with Exposure Compensation? RiceHigh Pentax DSLR Discussion 15 12-02-2006 06:27 PM
K10D auto Pop-up flash??? zizo Pentax DSLR Discussion 1 10-06-2006 05:57 PM



All times are GMT -7. The time now is 09:55 AM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top