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Archive 2012 · 1Dx.. Weird issue using on camera flash
  
 
vidoprof
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p.1 #1 · 1Dx.. Weird issue using on camera flash


So I am noticing that I have been having an issue with the 1Dx and using my 580 EX II on it using ETTL.

I set the camera to manual 1/160th at say ISO3200 (I shoot low lit business events).. I then put the camera on ETTL and I guess I thought the flash would expose properly for the rest. I notice in LR I have to up the exposure by 1+ sometimes 1.5+ to get a correct exposure.

Am I doing this totally wrong? SHould I be using AV mode instead of manual on 1/160th (I want to stop the people from moving and speaking and any motion and I would love to get above that even (I shoot with the 70-200 sometimes)..

Thanks
Ryan G




Nov 18, 2012 at 06:35 PM
Gochugogi
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p.1 #2 · 1Dx.. Weird issue using on camera flash


I'm guessing 1/160@F2.8 in M mode underexposes ambient and you're using auto flash to fill shadows and not as main light? Basically the camera assumes you're properly exposing the background and uses auto flash as fill light. Via the 580 flash menu, you could either disable E-TTL and use averaging mode , estimate FEC based on experience or use manual power settings. If you switch to P mode, the camera will automatically use flash as main light in dim conditions.

Av mode will expose the background correctly and use the flash to fill in shadows. In dim conditions you will need a tripod as shutter speeds will be really low even at F2.8. It's my fav mode save for super dim condition where I'd want to use the flash as main light and let the background go dark.



Nov 18, 2012 at 07:11 PM
BrianO
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p.1 #3 · 1Dx.. Weird issue using on camera flash


vidoprof wrote:
I set the camera to manual 1/160th at say ISO3200 (I shoot low lit business events). I then put the camera on ETTL and I guess I thought the flash would expose properly for the rest. I notice in LR I have to up the exposure by 1+ sometimes 1.5+ to get a correct exposure.


When the camera is in M, the 580EX II ETTL mode will use the flash as the main light, and should set the flash output for correct subject exposure. If your flash exposure isn't correct, make sure you have Auto Lighting Optimizer disabled, and make sure your Flash Exposure Compensation (FEC) is zeroed.

(You didn't say what aperture you used, but at 3200ISO the 580EX II should be powerful enough to handle any normal aperture at typical flash-to-subject distances.)



Nov 19, 2012 at 01:34 AM
BrianO
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p.1 #4 · 1Dx.. Weird issue using on camera flash


vidoprof wrote:
...SHould I be using AV mode instead of manual on 1/160th (I want to stop the people from moving...


Use Av (or Manual) when you want to control depth of field.
Use Tv (or Manual) when you want to control motion.
Manual, as you can see, gives you control of both DoF and motion.

In the situation you name, you should use M or Tv.



Nov 19, 2012 at 01:52 AM
vidoprof
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p.1 #5 · 1Dx.. Weird issue using on camera flash


Thanks guy for the tips.. I guess I could take a shot in AV.. get the proper exposure at say F5 then add in the flash for the fill.. or perhaps just do everything in M including the flash and then just keep the same distances when taking pics all around the rooms.

I thought ETTL would figure out (in M mode) how much flash I needed and compensate, but it didn't seem to do that the couple of times I tried it..

I will be experimenting some more. I will have to check on the Auto Lighting Optimizer (I need to read more on that too)..

Thanks and any other suggestions are appreciated.


Ryan G

Edit: Forgot to mention I shoot in RAW (in case that matters) to be able to get the most detail and save the photos when I mess them up.
Edit2: Auto Lighting Optimzer was always off (I just checked).



Nov 19, 2012 at 03:19 AM
BrianO
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p.1 #6 · 1Dx.. Weird issue using on camera flash


vidoprof wrote:
...Edit2: Auto Lighting Optimzer was always off (I just checked).


Hmmm. Not sure what the issue is then; you may just need to dial in +1 FEC on that camera to get the best exposure from ETTL. That's no big deal; set it and forget it, and you can then keep shooting in M or Tv, whichever you wish. (I prefer M.)



Nov 19, 2012 at 03:42 AM
diverhank
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p.1 #7 · 1Dx.. Weird issue using on camera flash


I have a 5DMk3 and 580EXII with auto lighting optimizer on and the exposure is spot on with camera on M and flash ETTL. Wonder what kind of diffuser the OP is using? Sometimes that tends to confuse the flash ETTL and underexpose. I use a Gary Fong clear dome and I found it's perfect if I have the white card up to bounce more light forward.


Nov 19, 2012 at 05:27 AM
 

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CW100
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p.1 #8 · 1Dx.. Weird issue using on camera flash


vidoprof wrote:
I thought ETTL would figure out (in M mode) how much flash I needed and compensate, but it didn't seem to do that the couple of times I tried it..

.


normally M mode does that but it also depends on ambient light




Nov 19, 2012 at 12:32 PM
vidoprof
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p.1 #9 · 1Dx.. Weird issue using on camera flash


I will keep testing.. Thanks guys and gals.. I appreciate the feedback..

Ryan G

p.s. I am using the Mini softbox velcro'd to the flash (wescott perhaps).. It's really tiny just to diffuse the light a little bit..



Nov 19, 2012 at 09:21 PM
BrianO
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p.1 #10 · 1Dx.. Weird issue using on camera flash


vidoprof wrote:
p.s. I am using the Mini softbox velcro'd to the flash (wescott perhaps).. It's really tiny just to diffuse the light a little bit..


Ah! That explains it! I didn't know you weren't using a bare flash.

The softbox reduces the output of the flash, but there's no "table of modifiers" in the software to tell the exposure computer how much loss there will be. The software thinks there a plain Speedlite zoomed to match the focal length of the lens.

Since ETTL flash exposure is based on measuring a preflash and extrapolating the required output from that, putting a modifier on the flash can affect the accuracy of the flash metering.

So, whenever you're using that modifier on that flash on that camera, just dial in +1 to +1.5 FEC (based on your previous experiences) and you'll be good to go.



Nov 19, 2012 at 09:37 PM
dwweiche
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p.1 #11 · 1Dx.. Weird issue using on camera flash


BrianO wrote:
...
Since ETTL flash exposure is based on measuring a preflash and extrapolating the required output from that, putting a modifier on the flash can affect the accuracy of the flash metering.
...


Is this a contradictory statement? If the camera, in E-TTL, determines exposure based on a pre-flash, shouldn't the modifier automatically be factored in? If the modifier reduces the pre-flash by let's say one stop, the camera will see one stop less from the pre-flash and thus increase output by one stop, no? I thought this is exactly how E-TTL works.

Where's Chuck Gardner when you need him

OP, if you want some light reading, this article has a ton of info. I think there's a section in Part II that covers how the camera works in the various metering modes.
http://photonotes.org/articles/eos-flash/



Nov 20, 2012 at 02:36 AM
BrianO
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p.1 #12 · 1Dx.. Weird issue using on camera flash


BrianO wrote:
...Since ETTL flash exposure is based on measuring a preflash and extrapolating the required output from that, putting a modifier on the flash can affect the accuracy of the flash metering....


dwweiche wrote:
Is this a contradictory statement? If the camera, in E-TTL, determines exposure based on a pre-flash, shouldn't the modifier automatically be factored in? If the modifier reduces the pre-flash by let's say one stop, the camera will see one stop less from the pre-flash and thus increase output by one stop, no? I thought this is exactly how E-TTL works.


One would think that it would work that way, but experience has shown that it doesn't. For some reason, modifiers mess up ETTL on many Canon bodies.

With my Vivitar 285HV I don't have that problem, because it's reading the actual reflected light from the subject during exposure. Modifiers aren't a problem, because I have an extension cord for the auto sensor so I can move it to the camera's hot shoe. The 580EX II has such a sensor, but it's fixed in place, so many modifiers will block it.



Nov 20, 2012 at 03:36 AM
diverhank
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p.1 #13 · 1Dx.. Weird issue using on camera flash


If we think about it, it makes sense that diffusers tend to underexpose. The ETTL measures the reflected light coming back from the flash through the lens. A diffuser tends to spread the light all over the place, lighting up the background. All of that gets reflected back to the flash ETTL sensor but the actual light lighting up the subject is only a part of the total and therefore a little bit darker.


Dec 03, 2012 at 07:55 AM





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