*Ist DL and TTL flash - Page 2

GregNS · 01-09-2007, 10:49 AM

Hi there,
This has been discussed at great length "elsewhere", but the DS and DS2 both have the TTL sensor.

With my DS2, if I set my Sigma EF 500 DG Super flash to "Program Mode" and have the aperture ring on "A" on my lens, then you get the default P-TTL behaviour (you can actually see the preflash through the viewfinder before the mirror goes up when you shoot).

However, if you move the aperture ring to a manual F-stop value (make sure your menu settings in the camera have been set to allow this and also make sure that your lens HAS an aperture ring - the DA lenses do not), then the camera reverts back to TTL.

I get PERFECTLY exposed flash shots at any distance (within reason of course

) both ways but the TTL mode does not include the Preflash and my daughter does not get caught blinking.

Hope this helps . . .

**Adam** · 01-09-2007, 01:05 PM

Ok, that clears a few things up.

In your example, you're using an A (or F, FA, FA J, DA, or DFA) lens. It's probable that the TTL will activate when the lens is set away form A, but the camera still knows what the max. aperture is.

What about M and K lenses, though? Why doesn't TTL work with them? Since both cameras have the sensor, why isn't it used to its full potential (i.e. including the built-in flash)? It's clearly all firmware-related, right?

GregNS · 01-09-2007, 03:35 PM

Hi there,
I have done this experiment with my SMC-A 35-70 as well as my FA 50 (f1.4) lenses. They both work. Unfortunately I cannot comment on the older M and K lenses as I don't have any.

This is just *slightly* off topic, but the thought just occured to me that P-TTL (or regular metering that is done with the meter in the viewfinder box while the mirror is down) actually meters "theoretically" since the aperture is still wide open at this point (not stopped down until the mirror is up I think).

TTL metering occurs while the camera is in the actual shot configuration (i.e. stopped down) hmmmmm hadn't thought of that before.

GregNS · 01-09-2007, 03:38 PM

Further to my experiment with moving the aperture ring away from "A", I am VERY grateful that I have some lenses that allow this.

With the Kit lens, I cannot get TTL behaviour out of my DS2. With P-TTL, my two sons are just fine, but my daughter ALWAYS blinks.

**Adam** · 01-09-2007, 04:44 PM

Well, it looks like we finally got everything straightened out.

For everyone that googles this thread, here's a quick summary of what we've finally concluded:

Pentax *ist D: Full TTL support for the internal flash and any external TTL flash used with any lens
Pentax *ist DS/DS2: TTL support for external TTL flashes only (Must be in M mode for manual lenses or when away from "A." Extremely fast apertures cannot be used)
Pentax *ist DL/DL2: No TTL support
Pentax K100D/K110D/K10D: No TTL support

Sadly, since the DS/DS2's both have the TTL sensor, the remaining flash functions must be disabled via firmware. Too bad for us

Also, if P-TTL is available on the external flash, it will be used over TTL.

BarneyCG · 01-10-2007, 06:13 AM

Originally Posted by Mo

Well, it looks like we finally got everything stranghtened out.

For everyone that googles this thread, here's a quick summary of what we've finally concluded:
Pentax *ist D: Full TTL support for the internal flash and any external TTL flash used with any lens

Pentax *ist DS/DS2: TTL support for external TTL flashes only when used with auto-aperture lenses set to "A" on the aperture ring

Pentax *ist DL/DL2: No TTL support

Pentax K100D/K110D/K10D: No TTL support

Sadly, since the DS/DS2's both have the TTL sensor, the remaining flash functions must be disabled via firmware. Too bad for us

I still don't think you are correct about the DS2 not supporting TTL with lenses in A mode ... do you include the DA series of leneses which have no aperture ring and thus are in A mode by default.

The reason I question this is because my GX-1S (DS2) and Metz 40MZ2 with the 3701 adaptor work perfectly well in TTL mode.

**Adam** · 01-10-2007, 08:53 AM

The list above is correct.

When you set the lens to A mode, P-TTL is used, if available. (This applies to A, F, FA, FAJ, DFA, and DA lenses)

GregNS · 01-10-2007, 11:29 AM

As for TTL in A mode:
I think the question is whether A mode would work with TTL if that is all the flash supports.

Many have claimed in the past that it does work. I'm not so sure. I have a great Pentax AF280T flash that has reliably given me beautiful TTL pictures with my old SuperProgram (Super-A elsewhere I think) body. It does NOT work with my DS2. It goes off at full strength for everything. I erroneously believed that this meant that my DS2 did not do TTL at all until I tried the "move the aperture ring to a manual f-stop" trick with my new Sigma EF500 DG Super flash.

Now I'm convinced that TTL does work with my DS2, (I can also see the sensor on the side of the image box behind the mirror).

Mo's assertion that the DS/DS2 will not do TTL in A mode DOES support my findings with the AF280T. I would tend to agree with him.

**Adam** · 01-10-2007, 02:29 PM

I did tests with the AF200T (see the previous page) and yes, it fires at full strength. The results are even worse for the built-in flash.

I'm glad we've finally gotten things straightened out

Matjazz · 01-10-2007, 04:19 PM

I just tested DS with AF220T, Sigma 18-50/2.8 DC EX lens (no aperture ring) and SMC-A 50/1.7 (aperture ring set to A). The exposure was right regardles of aperture shooting mode (P, Tv, Av, M) and aperture value.

**Adam** · 01-10-2007, 06:04 PM

Since the flash (assuming it's set to TTL) shoots at full power, all the shots expect those taken at the extreme apertures will be more or less correctly lit. The DL doesn't support TTL, sadly, so it's all luck, as we descussed on page 1.

If you set the flash to Auto, however, and set the aperture to the one indicated on the back, you'll always get correct exposure

mlaird · 01-12-2007, 08:14 PM

Originally Posted by Mo

[*]Pentax *ist DS/DS2: TTL support for external TTL flashes only when used with auto-aperture lenses not set to "A" on the aperture ring

I'm afraid this is incorrect for the *ist DS. I have been using my DS and my old Metz 32MZ-3 in TTL mode for a year and a half now, and it works fine. I never move the lens off the "A" setting except for playing around once in a while. I almost always shoot in aperture priority and set the aperture using the thumb wheel.

I usually bounce my flash off the ceiling to get better lighting, and the camera always compensates for that. Just to make sure, I just now ran a quick test. I shot a picture with direct flash at 1/45th, f/4.5 (wide open for my 20-35 zoom), and it was properly exposed. I then stopped down to f/5.6, f/8, f/11, f/16, f/22, and f/32 in turn, and each is identically exposed. Clearly the camera is controlling the flash power to adjust for the various lens openings.

I know that my Metz flash doesn't support P-TTL, although I wish it would. Please feel free to lobby Metz to come out with an SCA adapter that supports P-TTL! :-)

The *ist DS's TTL support seems slightly less consistent than when I was shooting film with my SF-1, but I think that's at least partly due to the exposure latitude of film and corrections during printing. The rest of the variation could be the reflectivity of the sensor that is supposed to be one of the reasons for switching to P-TTL.

-- Michael

**Adam** · 01-12-2007, 10:17 PM

It looks like I was indeed wrong. Here's the revised rule:

Pentax *ist DS/DS2: TTL support for external TTL flashes only (Must be in M mode for manual lenses, extremely fast apertures cannot be used)

I ran a few tests to confirm- the pics were only lit correctly when the ring was set to A. Thanks for pointing this out- the TTL's actually useful now!

**Adam** · 01-15-2007, 08:09 PM

Yet another small change

Since there's no need to keep this convoluted discussion going, please visit this thread to see what we've concluded: http://www.pentaxforums.com/forums/p...ttl-flash.html