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02-08-2017, 02:17 PM   #1
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Help with K-1 and Sigma EM-140 DG Ring Flash

Hi guys,

I am using a K-1 in combination with the Sigma EM-140 ring flash. It seems to have a synchronization problem, where maybe 1 out of 5 pictures is properly exposed. The flash always fires, but the image is dark. Just listening, it sounds like the shutter goes before the flash fires. I'm using it for dental photography and this is frustrating as time is valuable and patients hate waiting. Any advice on how to get them to synchronize is appreciated.

BTW, I've mainly been using the X-sync setting, 1/200 sec, F20, iso 200 if that helps with anything.

Thanks

02-08-2017, 02:26 PM   #2
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Sigma's page shows compaitbility only up through K-5, but that oculd simply be a product of not updating it:
https://www.sigmaphoto.com/flashes/flashes-resources/compatibility-table-em-140-dg-macro-flash

Have you tried it at slower sync speeds (1/180 or below)? Also, do you get the lag when both the camera body and the flash are set to manual?
02-08-2017, 02:49 PM   #3
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QuoteOriginally posted by Vote4Pedro Quote
Hi guys,

I am using a K-1 in combination with the Sigma EM-140 ring flash. It seems to have a synchronization problem, where maybe 1 out of 5 pictures is properly exposed. The flash always fires, but the image is dark. Just listening, it sounds like the shutter goes before the flash fires. I'm using it for dental photography and this is frustrating as time is valuable and patients hate waiting. Any advice on how to get them to synchronize is appreciated.

BTW, I've mainly been using the X-sync setting, 1/200 sec, F20, iso 200 if that helps with anything.

Thanks
Even in a bright dental office, I bet you could shoot at 1/120 F20 ISO 200 and the flash would be the only source of light the sensor would be seeing in the room. DCShooter's advice on lowering the shutter speed to test is a great one to try out. Set it to M, F20, ISO 200 and vary the shutter speed.
02-08-2017, 03:33 PM   #4
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QuoteOriginally posted by dcshooter Quote
Sigma's page shows compaitbility only up through K-5, but that oculd simply be a product of not updating it:
https://www.sigmaphoto.com/flashes/flashes-resources/compatibility-table-em-140-dg-macro-flash

Have you tried it at slower sync speeds (1/180 or below)? Also, do you get the lag when both the camera body and the flash are set to manual?

---------- Post added 02-08-2017 at 06:47 PM ----------

[/COLOR]
QuoteOriginally posted by bobbotron Quote
Even in a bright dental office, I bet you could shoot at 1/120 F20 ISO 200 and the flash would be the only source of light the sensor would be seeing in the room. DCShooter's advice on lowering the shutter speed to test is a great one to try out. Set it to M, F20, ISO 200 and vary the shutter speed.
Ok, I switched the flash to Manual, and it is working now! Thank you for the advice! It appears that the flash will work with any mode on the camera, but the flash must be in manual mode instead of TTL.
I don't understand the difference between TTL mode on the flash and manual mode. Is the TTL mode normally easier to use? What advantages does each mode offer? Do you think I could still get TTL to work, or is manual my only option?

Also, what is the purpose of X-sync mode?

Thanks


Last edited by Vote4Pedro; 02-08-2017 at 03:50 PM.
02-08-2017, 05:38 PM   #5
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The PTTL mode does a very quick preflash before the main flash in order to measure the actual flash exposure through the lens and adjust the flash output accordingly to maintain proper exposure. With manual, it's going to be a constant output value (which for dental applications might actually be preferred, since it will give more consistency across multiple exposures).

The flash will work in X-sync mode at any speed lower than the maximum speed at which the shutter can be fully open and completely expose the sensor to the flash output in a single burst. This is as opposed to high speed sync, in which the flash releases several timed bursts in order to expose different parts of the sensor, but which is lower in maximum output as a result.

Prior to the K-1, the max X-sync speed was 1/180 for Pentax DSLRs. The K-1 bumped the value up to 1/200. I wonder if since the flash is older, and Sigma is notorious for reverse-engineering signalling protocols rather than licensing them, that the higher sync speed has exposed a flaw in the implementation that is causing the main flash to fire slightly late when used in PTTL. Hence the suggestion to try a slower shutter speed. In M, there is no preflash; the shutter simply opens and the main flash fires, which I guessed (apparently correctly!) would remove any PTTL-related timing issues.
02-09-2017, 06:53 AM   #6
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For your application it is definitely better to go with all-manual settings, camera & flash. Determine what settings (f-stop, shutter speed, output power setting on the strobe) give the desired exposure and use those all the time. As noted by dcshooter, all-manual should provide near identical exposures for every shot*. PTTL even if working perfectly, may give slightly different exposures patient-to-patient as a consequence a little more of the lips, tongue or front teeth getting into an image when you want to show the molars.

*You should get absolutely identical exposures if you also: 1) always wait between shots long enough for the strobe capacitor to recharge fully (may take longer that just until the ready light illuminates); and 2) set your lens at one particular focal length = one particular distance lens-to-subject, and always use exactly that setting. With manual flash, if you move closer or father back the exposure might change.
02-09-2017, 10:22 AM   #7
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QuoteOriginally posted by dcshooter Quote
Prior to the K-1, the max X-sync speed was 1/180 for Pentax DSLRs. The K-1 bumped the value up to 1/200. I wonder if since the flash is older, and Sigma is notorious for reverse-engineering signalling protocols rather than licensing them, that the higher sync speed has exposed a flaw in the implementation that is causing the main flash to fire slightly late when used in PTTL. Hence the suggestion to try a slower shutter speed. In M, there is no preflash; the shutter simply opens and the main flash fires, which I guessed (apparently correctly!) would remove any PTTL-related timing issues.
This seems likely. I have a Metz flash, and noticed that there was a firmware update for it specifically to address compatibility with the K-1. It may not even be a flaw in the implementation so much as the fact that the new features of the K-1 didn't exist when the Sigma flash was designed.
02-09-2017, 11:31 AM - 1 Like   #8
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QuoteOriginally posted by bar_foo Quote
This seems likely. I have a Metz flash, and noticed that there was a firmware update for it specifically to address compatibility with the K-1. It may not even be a flaw in the implementation so much as the fact that the new features of the K-1 didn't exist when the Sigma flash was designed.
The Metz flash updates for K1 are because older units are programmed for APS-C format and do not communicate the correct focal length for FF, so the K1 "thinks" the flash output doesn't match the FL data coming from the lens. Hence, the F1 will not trigger the Metz. Some smaller Metz flash models cannot be reprogrammed with a USB link. Those models are generally being reissued in a "II" version that has correct FL data for FF = K1. Example: the tiny two AAA powered model 26 was reissued as a model 26-II that is K1 compatible.

07-22-2017, 06:00 PM   #9
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For what it is worth, I have some extra information to chip in to this thread, concerning the EM-140.

Having searched the 'net high and low for information on compatibility of the Sigma EM-140 (and Pentax 160FC) ring flashes with my Pentax K-01 and Pentax K3ii, I recently had the chance to put things to the test (for the Sigma anyway, no chance to even get sight of a S/H 160FC on Ebay...). On Sigma's website - as of 23 July 2017 - the newest model stated to be compatible with the EM-140 is the K5... hardly 'new' nowadays.

Compatibility Table EM-140 DG Macro Flash | Sigma Corporation of America

After multiple tests in indoor and outdoor lighting conditions, using my DA35 Limited Macro, I can confirm that (i) the EM-140 is working well on my K3ii (generally slightly over-exposing by 0.5 or 1.0 stop using P-TTL, which can be easily compensated for on the flash), and (ii) the EM-140 has serious problems on my K-01. Specifically, even if the flash is turned off, when mounting it onto the K-01 hotshoe the camera thinks that the flash is charged (non-flashing 'flash symbol' appears on display). That's crazy, yes? When the camera is set to P and the flash to P-TTL, almost without exception I get fully discharged flash white-out. Then I also noticed that the shutter speed seems to intermittently go from something close to the flash sync speed (1/80 - 1/100s) to something pretty long (1/2s to 1s). It does this at a frequency of about once a second. All this suggests to me that the flash connections / programming on the K-01 is non-standard compared with other Pentax digitals. Who knows why.... but this might also give some insights for others who are trying to get their 160FC to work with the K-01. I am thinking that something went wrong with the K-01 somewhere in its making...
09-22-2017, 07:49 AM   #10
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Something here is not right....

...I ordered and got an Sigma EM-140.
Have now used it some days on my K1 firm. 1.41. Lens DFA 100/2.8 WR. Also with PTTL -and if wanted autofocus with two piggybacked (hard to get) Kenko Pz-AF Uniplus Tube 25.
That is a total 50mm of extra extension and are able to autofocus as well - if wanted . Wow - what pics - just point and shoot.

By reading this thread I had worries before getting the unit and had thoughts of cancelling the order - but decided to at least test it.
However - all in all it worked as just out of the box as described.

Simply set the camera to AV-mode and use either manual focus or auto focus as I do with my other flashes.

Setup works with PTTL all the time.

As with other flashes in PTTL (as PTTL is often a bit tricky giving some over or under exposures) I often have to pre calibrate exposure by compensate a bit by changing the EV-value.

In a German forum "Pentaxians.de" - they have the same experience as I do.

Frage zum Makroblitz Sigma EM-140 DG ? Pentaxians

It seems that the OP there had heard rumours of this very thread and had worries as well.

However - that German thread shows that it should work all the time like as for me on the K1.

I think it's a great flash for a rather low price. Now I can recommend it.
The error mentioned here in this very thread must have another explanation. May it be settings, dirty contacts or something else?

(For those not knowing the German-language I hope Google translate might help.)
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