[erablesycomore]

Hello,
I just bought a Sigma EM140 ringflash for my K100D.

I chose it because it is fully P-TTL, I thought it would work perfectly.

Instead of this, I get strange exposure problems:

* I have done 10 times the same shot, with same ISO, aperture, shutter speed, same everything, and I have let enough time for the flash to recycle. between each shot.... BUT I get 5 times VERY OVEREXPOSED shots, and 5 times normally exposed shots

* I've done a macro shot (some animal figurines for babies) with camera in mode M : f/5,6 1/180s , flash auto TTL : good exposure
Same shot with camera in mode M : f/6,3 1/180s , flash auto TTL : VERY VERY OVERexposed
Same overexposure for f/8 or f/11 !
It's just random. The PTTL metering should adjust the light so that each shot (f/5,6 , f/6,3 or f/11) is well exposed.


The P-TTL metering system is just random with this flash + camera.

Lots of money wasted ?

Thanks in advance for any help!

[demp10]

Are you using a manual lens? If you are, any P-TTL flash will fire at full power regardless of camera and lens setting. If you are at the right distance/f-stop then you can get a correct exposure, otherwise it will be overexposed at shorter distances or under fro longer for a given f-stop.

[erablesycomore]

No, I use the standard 18-55, I don't use it in manual mode.
(I know a macro lense is better, but just for the exposure, it should work with this one).

If you are at the right distance/f-stop then you can get a correct exposure, otherwise it will be overexposed at shorter distances or under fro longer for a given f-stop.

Yes you're right, but this doesn't explain why at f/5,6 it's okay, and if I change it to f/6,3 the result is very very overexposed (not by 1/3 stop, much more).
Anyway, the result should be the same for f/5,6 or f/8 : the P-TTL system should take the aperture in consideration in order to have a good exposure.

[Bob from Aus]

To reset the flash - pull the batteries out and the flash will forget any settings and start fresh. I nearly always use mine in manual. I see no point in using it in any auto setting. I pick my aperture and then manually adjust the two flashes on the ring. I find for macro work that the flash need to be adjusted down and I am working at a known distance so it is dead easy. For minor adjustment I fiddle the aperture.

[erablesycomore]

To reset the flash - pull the batteries out and the flash will forget any settings and start fresh. I nearly always use mine in manual. I see no point in using it in any auto setting. I pick my aperture and then manually adjust the two flashes on the ring. I find for macro work that the flash need to be adjusted down and I am working at a known distance so it is dead easy. For minor adjustment I fiddle the aperture.

I want to use this ringflash for other things than just fixed objects (some photographers use ringflashes to shoot people, with some original results, etc.), that's why I don't want to use Manual mode + trial and errors shots.
I payed (an expensive price) for a P-TTL flash, so I don't understand why it is totally unreliable in PTTL ! Such a shame !

Is it the same for you (totally unreliable in PTTL) ?

Thanks a lot in advance

[Bob from Aus]

Sorry mate, I exclusively use it for macro.

Sigma back engineers its flashes. maybe it does not work with K100D. I found the distributor in Australia very helpful when I have had Sigma flash issues.

One other thought is to clean the contacts on your lens and camera around the bayonet mount.

If you still have problems Iet me know and I will set up my ring flash with several different bodies in PTTL. (Have K10 through to K5)

[lamented bovine]

Is it the same for you (totally unreliable in PTTL) ?

Thanks a lot in advance

Got the same unit. I have not noticed this with mine. How close are you to the subject? Try and run flash in high sync mode and ramp up your shutter speed.
To set flash, turn on in ttl and press + key until you see FP on screen. I generally shoot flash high speed sync F8 on. Take test shot and adjust accordingly.
Hope this helps it is a good flash.
Cheers
Macca

[erablesycomore]

I'm about 50cm from the subject.

No I don't want to use "high sync mode" : this mode was added on modern flash for situations where shutter speed needs to be > the camera sync speed, ie 1/180s for Pentax.
I don't need such high speed (I'm indoor), so I don't need FP mode (to make a comparison, using high speed sync mode here would be like using a scientific calculator in order to calculate "2 times 2" )

[lamented bovine]

I'm about 50cm from the subject.

No I don't want to use "high sync mode" : this mode was added on modern flash for situations where shutter speed needs to be > the camera sync speed, ie 1/180s for Pentax.
I don't need such high speed (I'm indoor), so I don't need FP mode (to make a comparison, using high speed sync mode here would be like using a scientific calculator in order to calculate "2 times 2" )

Ok, no probs. What camera mode were you in. I'll run mine and see if I get the same results.

[erablesycomore]

Hello, Thanks a lot lamented bovine !

It's a shot indoor of an animal figurine sitting on a white table, at 50 cm.

Camera : Mode M, ISO:200, shutter speed : 1/160 or 1/180s, f/5.6 no flash exposure compensation set on camera
Flash : PTTL, no flash exposure compensation set on flash

When I use the same settings at f/6,3 or f/8, or anything higher, sometimes it works, but sometimes it gives overexposure.

Do you obtain the same ?

[lamented bovine]

Hello, Thanks a lot lamented bovine !

It's a shot indoor of an animal figurine sitting on a white table, at 50 cm.

Camera : Mode M, ISO:200, shutter speed : 1/160 or 1/180s, f/5.6 no flash exposure compensation set on camera
Flash : PTTL, no flash exposure compensation set on flash

When I use the same settings at f/6,3 or f/8, or anything higher, sometimes it works, but sometimes it gives overexposure.

Do you obtain the same ?

Ok just run same settings as you. I am not getting your result. 1/160 f5.6 correct exp, @ f6.3 correct exp, @ f8 correct exp.
I dont have the 18-55, the closest I have is Sigma 50 1.4. Used K7. On the fence though if prob is with your flash.
Can you swap flash and try in store?
Cheers
Macca

[erablesycomore]

Thanks for having tried!

I just did 20 extra shots of test.

@f5.6 : correct exp, @f8 : bad exp @f5.6 : bad exp again @re-f5.6 with NO CHANGES : now correct exp

So the results are really unpredictable. 100% unreliable.

There should be a problem with either the K100D, or the Sigma 140.

I will try again...