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Thread started 08 Jul 2017 (Saturday) 03:31
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Flash at ISO400 issue

 
mcoren
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Jul 08, 2017 21:08 |  #16

John Sheehy wrote in post #18397421 (external link)
In limited ambient light, all I am interested in is a wide-open lens and a certain shutter speed. ISO is meaningless to me. If I add flash, I want it to add a little light and not dominate. I'm not sure what it is that you don't understand.

My apologies, I didn't mean for my question to sound so aggressive. Like I said, I agree that the camera's exposure system should produce the same results with or without fill flash. What I don't understand is why, if you're on auto ISO, and the value it chooses is meaningless to you, what's the problem if that value is 400?

I'm not challenging your statements, just trying to understand. I rarely shoot on M or use fill flash, so I'm not familiar with what you're trying to accomplish.

Mike


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mcoren
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Jul 08, 2017 21:13 |  #17

Wilt wrote in post #18397422 (external link)
A. I would! I can see the selected ISO value in the viewfinder (and top LCD), as well as my predetermined aperture and shutter speed. I know what shutter for motion control (the subjects and/or my camera) and aperture for DOF control...and I can see what ISO the camera has chosen for me. This is simply a different parameter (out of the triad of exposure controls: shutter, aperture, and ISO) compared to Tv or Av. Unlike automatic selection of Av and Tv, however, letting the ISO float does invite (too readily) getting high ISO noise. But having a menu setting for max ISO in auto ISO mode can overcome that issue somewhat.

That makes sense to me. Thank you. But I don't think that's what John was saying unless I'm just particularly thick tonight. I also still don't see what the problem is if the camera-selected ISO value comes out at 400.

Mike


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John ­ Sheehy
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Jul 08, 2017 21:28 |  #18

mcoren wrote in post #18397498 (external link)
My apologies, I didn't mean for my question to sound so aggressive. Like I said, I agree that the camera's exposure system should produce the same results with or without fill flash. What I don't understand is why, if you're on auto ISO, and the value it chooses is meaningless to you, what's the problem if that value is 400?

I'm not challenging your statements, just trying to understand. I rarely shoot on M or use fill flash, so I'm not familiar with what you're trying to accomplish.

Mike

I already told you what I am trying to accomplish: a small ratio of flash to my ambient exposure. My ambient exposure is dictated by the Av and Tv values, which I, as the operator of the camera demand. ISO 400 is not appropriate for those values, most of the time I would be using flash. The ambient would have too much noise from under-exposure, and the FEC would work off of target exposure of ISO 400; not my actual exposure which may be ISO 3200 or 25600, even though the camera chooses 400. That would result in almost all flash, and almost no ambient exposure.

I am not shooting statues in the shade; I am shooting living things that are very active and jump between dim, dark, dark and darker spaces with almost no red light, which can be upped quite a bit, even with FEC lower than -1. I don't like "mostly flash", in fact, I abhor it, unless it is indirect and diffused.




  
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Wilt
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Post edited over 3 years ago by Wilt. (4 edits in all)
     
Jul 08, 2017 23:34 as a reply to  @ mcoren's post |  #19

I understand what John Sheehy is complaining about 'nanny state'. So I set up my camera on tripod and dimmed the lights to reproduce his desired flash firing at the auto ISO value. I used a Metz 54MZ, which is about as powerful as a Canon 580EX.


  1. Ambient-only with Auto ISO was ISO 12800, 1/60 f/5.6
  2. I put my flash on photosensor mode, it could not reduce power sufficient to prevent overexposure with a subject at 6'.
  3. I increased distance to 15' and still ISO 12800 was too sensitive for the lowest power setting of the photosensor (non-eTTL) flash.
  4. I increased distance to 35' and still ISO 12800 was too sensitive for the lowest power setting of the photosensor (non-eTTL) flash even with f/5.6.

I had to drop ISO manually to ISO 3200 in order to not get a seriously overexposed shot at f/5.6

So what good is auto ISO selection of ISO 12800 to render proper ambient exposure at 1/60 and f/5.6, if the flash cannot drop its output sufficiently for those same settings?! It may be 'nanny'-ish but if you are unsuccessful in your attempt to shoot with flash, why should the camera let you try in auto ISO to attempt to use flash, if I have to have a subject past 70' or 100' in order to not overexpose?! I might as well have manually set ISO in trial and error chimping to discover what ISO would work with my flash.

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John ­ Sheehy
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Jul 09, 2017 09:18 |  #20

Wilt wrote in post #18397562 (external link)
I understand what John Sheehy is complaining about 'nanny state'. So I set up my camera on tripod and dimmed the lights to reproduce his desired flash firing at the auto ISO value. I used a Metz 54MZ, which is about as powerful as a Canon 580EX.


  1. Ambient-only with Auto ISO was ISO 12800, 1/60 f/5.6
  2. I put my flash on photosensor mode, it could not reduce power sufficient to prevent overexposure with a subject at 6'.
  3. I increased distance to 15' and still ISO 12800 was too sensitive for the lowest power setting of the photosensor (non-eTTL) flash.
  4. I increased distance to 35' and still ISO 12800 was too sensitive for the lowest power setting of the photosensor (non-eTTL) flash even with f/5.6.

I had to drop ISO manually to ISO 3200 in order to not get a seriously overexposed shot at f/5.6

So what good is auto ISO selection of ISO 12800 to render proper ambient exposure at 1/60 and f/5.6, if the flash cannot drop its output sufficiently for those same settings?! It may be 'nanny'-ish but if you are unsuccessful in your attempt to shoot with flash, why should the camera let you try in auto ISO to attempt to use flash, if I have to have a subject past 70' or 100' in order to not overexpose?! I might as well have manually set ISO in trial and error chimping to discover what ISO would work with my flash.

What difference does it make? You would have lost the shots either way, if you didn't chimp and make appropriate adjustments. Manual ISO would have allowed more room for error, though, on the side of ambient under-exposure with the full FEC for flash, if you forgot to raise the ISO when appropriate. The purpose of auto-ISO is not to say to the camera, "I give up; you take over". It is to say to the camera, "set the ISO to what I would have done myself based on metering, if I had the time". That is what automation is really supposed to be; not surrender to seeming camera whims. The more you direct the camera to think like YOU (but faster), the more automated it is.

I can tell you that when someone reminded me of the function of ISO Safety Shift and I used it on my 6D with a 550EX and a Better Beamer, which concentrates the light, with a slow telephoto lens with TC, I never had an epidemic of flash-blown shots with the ISO set to 25600+HTP, -2/3 EC and -2FEC, shooting birds in the deep shade at 1/400 - 1/800. Many of the shots were in fact taken at ISO 25600.

You seem more intent on picking at my criticism of Canon's implementation, than coming up with solutions:


  1. Use a higher shutter speed with HSS. Much lower guide number, as much flash hits the shutter curtains.
  2. Use HTP, so if the flash part of the exposure gets too high, there is room for it. HTP works wonders for leaving headroom without darkening the default conversion or review images. There should be more than one stop available at higher ISOs. If the camera used lower analog gains for higher ISOs, too much flash could shift the balance more towards flash without actual RAW clipping. Cameras are far too JPEG-oriented.
  3. Use negative EC for the ambient exposure, which I consider normal procedure when flash is going to add more light, unless I am going for carefully calculated ETTR at base ISO! High ambient exposure leaves less room for flash before clipping. Negative EC drives the auto-ISO a little bit lower.
  4. Use a TC instead of cropping. A TC lessens the chance of flash over-exposure.



  
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Gel
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Post edited over 3 years ago by Gel. (3 edits in all)
     
Jul 09, 2017 10:05 |  #21

Bassat wrote in post #18397405 (external link)
You are aware that you can set ISO to anything you want, right?

Yes buddy, 350 weddings in I know I can do that. Just that there are times where if I did pump the iso the shutter speed would end up being faster than the x sync, the camera would them limit the shutter speed and the exposure runs the risk of blowing. The camera thinks much quicker than me so I can focus less on the settings and more on what I'm shooting. Just that the arbitrary ISO400 in auto iso mode without any fluidity of that setting is a problem.

It's great to set a minimum shutter speed and only have to worry about aperture in Auto ISO / AV mode. Then ISO400 screws it up when I turn on the flash. Considering I've set the minimum shutter speed a 1/125 a sec I don't feel it should drop down to 1/30 because of that ISO limitation when flash is used.

Custom functions are one way I guess but settings need to change at critical moments and things can go wrong when in a hurry.


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Wilt
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Post edited over 3 years ago by Wilt. (7 edits in all)
     
Jul 09, 2017 13:03 |  #22

John Sheehy wrote in post #18397767 (external link)
You seem more intent on picking at my criticism of Canon's implementation, than coming up with solutions:


  1. Use a higher shutter speed with HSS. Much lower guide number, as much flash hits the shutter curtains.
  2. Use HTP, so if the flash part of the exposure gets too high, there is room for it. HTP works wonders for leaving headroom without darkening the default conversion or review images. There should be more than one stop available at higher ISOs. If the camera used lower analog gains for higher ISOs, too much flash could shift the balance more towards flash without actual RAW clipping. Cameras are far too JPEG-oriented.
  3. Use negative EC for the ambient exposure, which I consider normal procedure when flash is going to add more light, unless I am going for carefully calculated ETTR at base ISO! High ambient exposure leaves less room for flash before clipping. Negative EC drives the auto-ISO a little bit lower.
  4. Use a TC instead of cropping. A TC lessens the chance of flash over-exposure.

Your interpretation of my actions, no clue as to my motivations in conducting the test but unfounded speculation.

My motivation:
I had previously posted about the rationale of chooing ISO 400 based upon inability to regulate flash power. My test was MANUAL selection of ISO (after Auto ISO had suggested 12800 for 1/50 f/5.6) to follow up on Bassat's earlier comment, "You are aware that you can set ISO to anything you want, right?" I wanted to see what doing exactly what he proposed would accomplish, practically speaking. Ergo my test, the results of which found that even at 35'-40' distance and f/5.6 the flash seriously overexposed the shot unless dropping ISO manually from 12800 to 3200. IOW, even the 'set ISO manually' was not a workaround to the auto ISO original suggestion of 12800!

Gel wrote:
Just that the arbitary ISO400 in auto iso mode without any fluidity of that setting is a problem.

My conclusion from my test:
The nanny state was not the restriction, the inability of the equipment to cope is the restriction. If the equipment could support the use as described by Bassat, but the artificial limitations imposed by Canon design prevented them from happening (without manual intervention) I can subscribe to 'nanny state arbitrary ISO400' limitations line of thinking, but the equipment simply cannot do it well enough (yet)


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Flash at ISO400 issue
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