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04-24-2016, 11:53 PM   #16
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It's a great demonstration of a changing lighting balance between flash exposure and ambient exposure, complete with the colour balance shift that entails when there is tungsten lighting. For whatever reason your ambient exposure (controlled by aperture, ISO and shutter speed) has varied recording more ambient light on the yellow first one. In the second that ambient exposure is less and so no yellow tone.

The P-TTL flash exposure remained constant and gives that cool metallic colour tone. A mixture of the the two is probably a nice balance, and the flash white balance could be warmer to look more natural. It's a great demonstration of why it's necessary to take control of flash situations with manual camera exposure mode, a fixed ISO, and automatic flash exposure.


Last edited by mcgregni; 04-25-2016 at 12:10 AM.
04-25-2016, 12:14 AM   #17
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The difference is....

Flash duration. With the high iso the flash fired for a shorter duration to give proper exposure , more available light registered. Lower iso the exposure was influenced more by the whiter longer duration light from the flash. Proper behaviour
04-25-2016, 12:23 AM - 1 Like   #18
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That doesn't sound correct to me. The flash exposures look consistent . The background ambient exposure is influenced by ISO and/or exposure time changes. It looks like the first one has recorded a higher ambient exposure for one of those reasons.

Looking back at those EXIF figures provided earlier, it is the ISO that has varied (as others have said) ... from 125 to 3200 apparently. At 125 the ambient background has not really recorded with any natural light, so we just see the spill over from the flash. But at 3200 the ambient exposure is quite high, giving the full effect of the tungsten colouring and brighter appearance. There is some ambient spill over into the flash-lit subject area, but mainly the subject exposures are the same.

In fact the P-TTL system has done very well to control the flash output so well at such a high ISO and close distance!

Last edited by mcgregni; 04-25-2016 at 02:28 AM.
04-25-2016, 02:02 AM   #19
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Simple: don't use flash with TAV. Fix your ISO speed by using Av.

04-25-2016, 02:37 AM - 1 Like   #20
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Good advice. I keep giving it but there are still plenty of photographers who seem to want and expect the camera automations to take all of those decisions out of their hands with flash photography, which is unrealistic I think ... well, at least if you want to get pictures looking consistent how you want them to (talking generally here, not directly to the OP ...)

Just because an automatic function is available in certain configurations does not mean that it should be relied upon and replace photographer knowledge and control. Flash and ambient light balancing is one technical area where camera electronics cannot make the right decisions in every situation. My own approach is to use Manual camera exposure mode, fixed ISO and P-TTL flash exposures (with flash compensations) to easily control this balancing.

I appreciate that the OP here was not asking for lessons, so I apologise if this seems like that .... you were asking why the automatics have varied things so much .... but its inevitable that the discussion turns to the alternative approaches. Truth is, I don't think we know why the automatics vary so much ..... that's down to the designers and the complex algorithms they program in .... algorithms however that are doomed to fail frequently.
04-25-2016, 04:43 AM   #21
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QuoteOriginally posted by mcgregni Quote
Good advice. I keep giving it but there are still plenty of photographers who seem to want and expect the camera automations to take all of those decisions out of their hands with flash photography, which is unrealistic I think ... well, at least if you want to get pictures looking consistent how you want them to (talking generally here, not directly to the OP ...)

Just because an automatic function is available in certain configurations does not mean that it should be relied upon and replace photographer knowledge and control. Flash and ambient light balancing is one technical area where camera electronics cannot make the right decisions in every situation. My own approach is to use Manual camera exposure mode, fixed ISO and P-TTL flash exposures (with flash compensations) to easily control this balancing.

I appreciate that the OP here was not asking for lessons, so I apologise if this seems like that .... you were asking why the automatics have varied things so much .... but its inevitable that the discussion turns to the alternative approaches. Truth is, I don't think we know why the automatics vary so much ..... that's down to the designers and the complex algorithms they program in .... algorithms however that are doomed to fail frequently.
Ah but a lesson is indeed what I needed apparently. No where in my camera manual does it explain why this was happening. I also noted that there are not as many options for flash control in TAV mode as there are in the AV mode. Could this reason be somehow connected with how the camera is exposing differently between the two modes?

---------- Post added 04-25-16 at 05:48 AM ----------

QuoteOriginally posted by beachboy2 Quote
Simple: don't use flash with TAV. Fix your ISO speed by using Av.
This seems to be the obvious route but there are many times when I need to control my shutter speed as well as my aperture but would happy to let the camera control the ISO on the fly. In most cases this is the best/easiest option for me especially when conditions are changing quickly as I am not good enough to handle the ISO manually during these fast paced situations.
I will practice using ev compensation to adjust the ISO while I'm using flash in TAV mode.
All the reset of the explanations are much appreciated.
04-25-2016, 05:13 AM   #22
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No, the camera manuals don't offer much 'explanation' at all! They seem to assume a good deal of background photographic and DSLR specific knowledge.

The only different flash option I'm aware of between Av and Tav mode would be 'Slow Speed Sync' plus the associated red-eye reduction flash modes ... This is because Slow Speed Sync is not required in Tav mode as you have direct control over time value (shutter speed).

The only other obvious variable is auto-ISO in Tav mode, which I guess I've made clear enough already I don't think is a good idea.

To be honest you'll be fighting a losing battle with flash photography to keep using auto ISO and compensations to try and gain control over ISO. It's much better to gain control over your flash exposure with a fixed ISO that is suited to the conditions (no, the camera cannot decide this for you) , use flash compensation to control flash exposure, and in Manual camera mode change the shutter speed to adjust the amount of ambient light recorded.

Last edited by mcgregni; 04-25-2016 at 05:34 AM.
04-25-2016, 05:13 AM   #23
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You can always limit your ISO range through the menu, ie: 100-400 or what have you and still use Tav mode.

Eric.

04-25-2016, 05:48 AM - 1 Like   #24
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That might reduce the variables and inconsistencies, but it doesn't address the central problem which is that automatically changing ISOs don't work for flash photography. What if the conditions actually demand an ISO of 800 or 1600? The point is to have a suitable fixed ISO for good consistent flash work.

What ISO is suited depends on two things .... The ambient brightness (assuming you want to record some of that light) and the flash to subject distances. For the ambient light the ISO needs to be high enough to allow a fast enough shutter speed for steady shots while still recording enough natural light ....so, for example, in a domestic room in low tungsten light it might need ISO 1600 at 1/60th sec , but in a bright daylit room it might be ISO 200 at 1/125.

For the distances, if you are going to bounce off a high ceiling, or at an extreme angle and the subject is standing away from the wall, then ISO 3200 might give you easy flash exposures without the flash working too hard and recycling being too slow, but for smaller bounce angles and distances or directly facing flashes where the subject is close, them ISO 400 may be more appropriate.

Considering these factors and taking a positive decision for each situation is going to lead to far better and consistent flash photography than any camera automatic operations.
04-25-2016, 08:31 AM   #25
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QuoteOriginally posted by mcgregni Quote
That doesn't sound correct to me. The flash exposures look consistent .
If the flash duration was the same, the high ISO picture's foreground would have been massively over-exposed by the flash.
04-25-2016, 08:44 AM   #26
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OK, yes, in technical terms the flash exposure is controlled automatically by the flash duration, I understand your point. Sorry, I thought you were saying that it was the flash duration that was causing the difference in ambient background brightness.

I'm not seeing the flash exposure here as the issue .... rather the background exposures varying caused by the ISO differences.
04-25-2016, 09:28 AM   #27
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QuoteOriginally posted by jayman_1975 Quote
Yes this is exactly what I have found. I wonder why they would have it act this way. I prefer to shoot in TAV mode but when I use the flash I find it over over exposes badly because it doesn't account for it. Seems like a bad design flaw
I wouldn't call it a design flaw. I like shooting in TaV for birds. On the main menu for the K-3 and I think you can do it on the K-5, you can preset your ISO so it will not go above or below certain numbers. I like to set my K-3 at an upper limit of 800 ISO.

Press the INFO button then use the set of four crescent shaped keys to go to "ISO AUTO Setting Adjustment Range"

Last edited by traderdrew; 04-25-2016 at 09:43 AM.
04-25-2016, 10:32 AM   #28
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QuoteOriginally posted by jayman_1975 Quote
I have taken two identical pics one in TAV mode and one in AV mode. Identical settings both on Auto ISO. I cant figure out why the camera chooses to use such different ISO values between the two pics. This is with my K5iis but also does the same thing with my K-01.





The first was taken in TAV mode, second in AV mode. I have noticed that this happens all the time but i dont know why.
The camera follows rules on shutter speed aperture and ISO all while attempting to provide the minimum requirements for exposure .

this has long been a topic with respect to the way the camera is programmed. It will shoot to get hand held exposure based on ISO, aperture and shutter speed. In TAV mode it has control of only ISO where in AV mode it has more control to move things around because it has shutter and ISO. Depending on what the camera selects for the exposure background is more or less pronounced because flash falls off at the square of the distance.

The real story here is for flash, you, not the camera need to make decisions. I always use manual in flash. Note manual exposure does not mean lack of auto flash, just that you control 100% of the base settings,M aperture shutter and ISO,

Depending. On the desired look, I will expose for background neutral, (fill flash only) or for slight background separation about -1 stop so flash dominates the subject and the background is about 1 stop down, to the background completely black by separating with distance and manually setting exposure for background at about -4 stops.

Letting the camera make all the decisions you may as well use an I phone

Last edited by Lowell Goudge; 04-25-2016 at 10:38 AM.
04-25-2016, 10:42 AM   #29
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From what I can tell.. This is due to the ISO setting. In case of higher ISO the sensor is more sensitive (d'oh) and ready to capture a lot of light and hence a programmed exposure fires the flash at much lower power (shorter duration). In case of a lower ISO setting the flash power has to be increased as much as the stops lost by the reduced sensitivity. So the exposure of the subject is consistent but the background light capture isn't and is due to the fact that more flash power is put up and the sensitivity is lower (which captures less ambient light).
The second exposure is considered bad in my opinion. It is unbalanced use of flash power/ISO in case of a programmed exposure (Av, Tv, Sv, TAv and P are all programmed exposures).
04-25-2016, 11:38 AM   #30
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Just a little imput,..... aperture, shutter then ISO are things I learned about in that order. I find myself adjusting my exposure compensation out in the field and I believe it's just as important.
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