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03-13-2019, 12:43 AM | #1 |
Pre readings differ from Post Playback EXIF under these conditions... what gives?
** Quite Confused, Need Pro Help ** I am just doing some testing at home and have noticed something peculiar happening with my K-1 + flash that I have never noticed before. Ok so the set up is K-1 with FA43 with a V6ii attached (tripodded). The flash going to be used is a Cactus RF60x (also on lightstand). The purpose of my tests is to analyse various light modifiers on Davo (my mannequin) but that's not really important right now. I am in Av mode and have set a -1.7EV, at this time the V6ii is OFF. I have my ISO Auto Settings set to 'Fast' which means my shutter speed is not dropping below 1/125 at this time. I take a test shot without firing flash (to demonstrate a 'before' modifiers are introduced shot) and I have the following settings before AND after (important point the 'before and after, more on this later). I get before the shot; 1/125 f1.9 ISO AUTO (1600) << it shows the value you're going to get) -1.7EV I take the shot and upon review those are indeed the settings the playback screen says (important!). So now I toggle the V6ii ontop of the K-1 to being on (Tx mode), I am in P-TTL mode (HSS supported but unlikely needed as it's a pretty dimly lit room) and what I noticed from toggling on in this Av Mode is I immediately LOSE half my shutter speed, I drop down to 1/60 despite have ISO set to AUTO (and of course aperture still at f1.9). My take away message from this is that the ISO Auto Settings (Slow, Normal and Fast) are NOT taken into consideration when flash is connected and armed. Confirm anyone? But here's where it gets really weird. So I take a shot anyway, and before the shot it says; 1/60 f1.9 ISO AUTO (but now no preview of what the ISO will be!) -1.7EV The shot ends up with the same values and gives a well balanced shot with ISO 400. Cool. But... there's more! So now I toggle out of AUTO ISO, I don't like the idea of 'running and gunning' at an event with 1/60, I would like more shutter speed, and in Av mode the only way to do that is to bump ISO up, so I take it out of Auto ISO and set it at what the initial test shot gave and fix at ISO 1600. Now before the shot is taken I have these readings showing; 1/160 f1.9 ISO 1600 (fixed, not Auto) -1.7EV I take the shot and upon REVIEWING IN PLAYBACK it is now telling me my shutter speed is actually 1/200?!?! (every other value the same). I figure it's a fluke, just at the moment I take the shot ambient light changes whatever, so I repeat again and again, even at different ISO's. Nope... playback is everytime giving me higher shutter speeds than what the reading says I'm going to get. 1/200 before the shot, 1/250 in playback etc. What is going on? PS: There are many ways in which to use flash in photography. When in a controlled studio environment whether it be portrait work or product photography you do not wish for any automation anywhere, in fact you often want to kill ambient light completely. This is where Manual Mode and getting out of P-TTL and into Manual flash power is a must. But is this the only instance flash is used? No... It can also be used in events, something like a wedding, whereby the tog is shooting at a reception, walking around in differing lighting conditions, or perhaps someone shooting in Australia where it's 1/8000 sec outdoors and as soon as you shoot into shadows under a tree it's 1/2000, step inside or onto a verandah, 1/400 and into a house 1/100. Av mode is very handy mode to control your shutter speed, and if you have delved enough into the menu system you will know that Slow, Normal and Fast Auto ISO settings can assist with always retaining a fairly safe shutter speed and make the automation of the camera prefer to bump the ISO up before lowering shutter speed. But that's not all, many of you are probably unaware that in Av mode you can also easily fix ISO instead of it being Automatic, that means 2/3 exposure triangles are now fixed with only shutter speed being the automatic variable. It's pretty close to shooting Manually with a little helping hand to ensure things go smoothly. And it's during these types of events where you run and gun with flash (not all flash shots, just some) where you want to illuminate the subject a little more but DON'T HAVE TIME to adjust every setting (from both the camera and flash) or get things 100% perfect that P-TTL with Av can come in handy. You can get a very nice effect from a simple -1EV in camera value and a 0.0 flash, or +1.0EV comp flash in P-TTL (depends on distance and lens used and walls to bounce off etc). But typically you can dial in quite quickly some pleasing EV+/- values for camera and flash in a running and gunning scenario that gives great results. EDIT: I just tested with my AF360FGZII, and the same applies, the pre reading in Av+P-TTL is not the same as EXIF Playback, it's giving me higher shutter speeds than it said I was going to get. Last edited by BruceBanner; 03-13-2019 at 12:49 AM. | |
03-13-2019, 01:14 AM | #2 |
The final exposure when using P-TTL is set during the preflash which is emitted right before the frame is exposed by the main flash. I would therefore not expect to see the same before and after settings when in P-TTL mode. | |
03-13-2019, 01:28 AM | #3 |
Interesting, but this doesn't seem to occur in Manual Mode (camera) when in P-TTL (it's too dark now to test that properly but will try tomorrow but am sure the readings stay the same in that mode). So this is a Av+P-TTL thing vs a P-TTL only thing I think | |
03-13-2019, 01:54 AM | #4 |
As others have said , it only decides on what to use after the pre-flash. | |
03-13-2019, 02:02 AM | #5 |
in manual mode the camera will adjust output from the flash only to give the exposure. In Av mode it will change the flash output and ISO if set to AUTO-ISO. It may also change the shutter speed depending on ambient light. As others have said , it only decides on what to use after the pre-flash. Try it. Get a 360II or 540II, be in Av mode, P-TTL on flash. Fix the ISO, fix the aperture (obviously lol), record the shutter speed, take the shot, review the shot on the playback, see that the shutter speed is higher everytime regardless of what ISO you choose than it said it was going to be before the shot was fired. | |
03-13-2019, 02:53 AM | #6 |
As has been explained already, what you see on the screen or viewfinder before firing is not what you will get, because the automated aspects of the exposure settings are not calculated until the pre-flash. Bruce, you're forgetting about the most important setting here ... What is your camera flash mode. ...? Don't forget, most of this is covered in my Supplement PDF guide, a whole section on automatic flash photography. | |
03-13-2019, 03:32 AM | #7 |
As has been explained already, what you see on the screen or viewfinder before firing is not what you will get, because the automated aspects of the exposure settings are not calculated until the pre-flash. Bruce, you're forgetting about the most important setting here ... What is your camera flash mode. ...? Don't forget, most of this is covered in my Supplement PDF guide, a whole section on automatic flash photography. I wonder now if using Sv or Tv mode with P-TTL is also 1/4 stop shifting an automated thing? Flash mode, for the AF360FGZII I just turned it on, that's all, P-TTL and fire. Cactus V6ii same thing, obviously TTL for the V6ii, and the RF60x was just Group A/Mode A etc. Both systems doing the same trick tho, shifting shutter speeds during the shot. | |
03-13-2019, 03:49 AM | #8 |
No, the Camera Flash mode, on your camera .... That is the important setting that influences automated ambient exposures in these circumstances. Still recommending you read up the Supplement section of my guide.
| |
03-13-2019, 04:18 AM | #9 |
I have your supplement thingy, I read it ages ago before I knew any of this... it made zero sense to me back then (a good 1-2yrs ago), and I think you know me better now and can probably say hand on heart it still will make zero sense to me (but no seriously, I will have a look at it again). | |
03-13-2019, 04:23 AM - 3 Likes | #10 |
The camera flash modes are also detailed in a special section early on in the main Guide document (2nd edition). Worth having another stab at understanding it really ...... Honestly, most of your forum threads here are way more complicated than my guides!! Anyway (and you always knew this was coming!), you asked for the pro view on this. Well I'm not a pro, but I am very sure that the pros wouldn't even be bothering to think about any of this ..... They just wouldn't care ..... Ok, deep breath, here it comes again..... When trying to control and mix ambient and flash exposures, use Manual camera mode and fixed ISO. Last edited by mcgregni; 03-13-2019 at 04:29 AM. | |
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03-13-2019, 05:38 AM - 2 Likes | #11 |
The key here is that before the pre-flash, the camera can only see the ambient light levels and has no clue how much or how little light the flash might add. The settings it shows are probably conservative. After the pre-flash, the camera knows how much light the flash is going to contribute and that might cause the camera to change whatever settings it's allowed to manage the balance between ambient and flash. In Av mode, it might speed up the shutter time a bit. In Tv mode, I'd not be surprised if you see the same fraction of a stop closing of the aperture in the post-shot exposure settings. | |
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03-13-2019, 07:09 AM - 1 Like | #12 |
I keep on with the same mantra over and over, in any Flash threads that concern automated exposures and auto -ISO .... If we want full and secure control over the images (and Professional work always demands this, regardless of the scenario), then we cannot rely on auto exposure parameters in addition to our P-TTL flash levels. P-TTL itself, by itself, is a good thing and a useful aid to efficiency, but only when its the one single variable to focus on. Automated flash metering needs a solid, fixed base in terms of the ambient EV, not the least in order to allow the photographer to see clearly the precise effect of their compensation adjustments. Trying to view and assess the impact of multiple automated setting responses, as well as juggle two independent compensation inputs ....well, it's all too much and bound to lead to confusion and inconsistently exposed shots. I do agree that it's good thing to have a basic underlying knowledge of the key aspects of what the automated systems are trying to do, and what they respond to .... That's why I wrote sections in my Guides that cover Camera Flash Modes, the impact of focal length, ambient brightness, program line, auto-ISO parameters etc. But to understand these basic principles is to ultimately appreciate the liimitations of such an automated approach to what is a very complicated thing; the balance of light and darkness in a scene, and the creative desires of the photographer who needs to take control of that scene and produce an image that records a precisely controlled mix of ambient and flash exposures. No tiny camera computer brain can do that | |
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03-13-2019, 12:09 PM - 1 Like | #13 |
Your initial issues are most likely the result of coupling EC with Av mode and flash with auto-ISO. As you may be aware, my position is that auto-ISO is evil and should be avoided unless doing snapshots in much the same way as green mode should be avoided. Even with auto-ISO turned off, EC with flash in Av mode may result in a shift in shutter speed for the actual exposure.* If you want control of the shutter speed and aperture, M-mode is your best bet. Remember too, that the EC settings on the body are for ambient light exposure, not the flash EC. (...yes, all covered in comments above, but I could not resist a few keystrokes on this topic.) Steve * Reasons are complex and have to do with Last edited by stevebrot; 03-13-2019 at 12:45 PM. | |
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03-13-2019, 01:18 PM | #14 |
The camera flash modes are also detailed in a special section early on in the main Guide document (2nd edition). Worth having another stab at understanding it really ...... Honestly, most of your forum threads here are way more complicated than my guides!! Anyway (and you always knew this was coming!), you asked for the pro view on this. Well I'm not a pro, but I am very sure that the pros wouldn't even be bothering to think about any of this ..... They just wouldn't care ..... Ok, deep breath, here it comes again..... When trying to control and mix ambient and flash exposures, use Manual camera mode and fixed ISO. FWIW I have posted this on the Facebook Pentaxian site as well, it's caused quite a stir with some event photographers saying they use Manual and I'm wasting my time in Av mode (surprise surprise ), whilst a few other pros have come to my support advocating running and gunning in Av mode with a degree of constraint (fixed ISO etc) can actually be a fantastic combo with P-TTL So calm down! You are helping! I get it! When introducing P-TTL flash your exposure triangle goes into a square with a 4th variable contributing to the shot, Av Mode is suicide! Leaving only Aperture in control of the user and letting the system try and figure out what to do with the other 3 variables is going to be problematic. However I think a lot of people forget that ISO can be fixed in Av Mode, without a flash that's controlling 2/3 variables, and with flash in P-TTL it's 2/2 (still not ideal but not as wildly bad as you might think). X Mode is my most favourite flash mode anyway :P The key here is that before the pre-flash, the camera can only see the ambient light levels and has no clue how much or how little light the flash might add. The settings it shows are probably conservative. After the pre-flash, the camera knows how much light the flash is going to contribute and that might cause the camera to change whatever settings it's allowed to manage the balance between ambient and flash. In Av mode, it might speed up the shutter time a bit. In Tv mode, I'd not be surprised if you see the same fraction of a stop closing of the aperture in the post-shot exposure settings. Could it be that if the flash in P-TTL mode is firing it's weakest version and the exposure will still be too much it then has to bump something up for the shot so raises the shutter speed? I shall test with Sv and Tv mode and report back. I keep on with the same mantra over and over, in any Flash threads that concern automated exposures and auto -ISO .... If we want full and secure control over the images (and Professional work always demands this, regardless of the scenario), then we cannot rely on auto exposure parameters in addition to our P-TTL flash levels. P-TTL itself, by itself, is a good thing and a useful aid to efficiency, but only when its the one single variable to focus on. Automated flash metering needs a solid, fixed base in terms of the ambient EV, not the least in order to allow the photographer to see clearly the precise effect of their compensation adjustments. Trying to view and assess the impact of multiple automated setting responses, as well as juggle two independent compensation inputs ....well, it's all too much and bound to lead to confusion and inconsistently exposed shots. I do agree that it's good thing to have a basic underlying knowledge of the key aspects of what the automated systems are trying to do, and what they respond to .... That's why I wrote sections in my Guides that cover Camera Flash Modes, the impact of focal length, ambient brightness, program line, auto-ISO parameters etc. But to understand these basic principles is to ultimately appreciate the liimitations of such an automated approach to what is a very complicated thing; the balance of light and darkness in a scene, and the creative desires of the photographer who needs to take control of that scene and produce an image that records a precisely controlled mix of ambient and flash exposures. No tiny camera computer brain can do that But also I thought the fact that flash overrides the Auto ISO setting of Fast, Normal and Slow was kinda interesting, I didn't know it did that (irrelevant anyway as I took it out of Auto ISO for the actual shots producing that differing shutter speeds. What is interesting is everyone talks about inconsistent exposed shots but I've actually seldom had that ever when shooting in Av and P-TTL. Things typically work out great. It could be that even when in the past I have been in AUTO-Iso, the fact that the EV comp is -1.0 and the flash exposure left at 0.0, it just produces a decent result. Where it gets problematic in terms of exposure is getting too close most of the time. Anyway, just thought I might mention that... Your initial issues are most likely the result of coupling EC with Av mode and flash with auto-ISO. As you may be aware, my position is that auto-ISO is evil and should be avoided unless doing snapshots in much the same way as green mode should be avoided. Even with auto-ISO turned off, EC with flash in Av mode may result in a shift in shutter speed for the actual exposure.* If you want control of the shutter speed and aperture, M-mode is your best bet. Remember too, that the EC settings on the body are for ambient light exposure, not the flash EC. (...yes, all covered in comments above, but I could not resist a few keystrokes on this topic.) Steve * Reasons are complex and have to do with pre-flash intensity and minimum/maximum attenuation of the main flash. Remember that flash is applied in addition to ambient. If the combo is too bright, increasing the shutter speed may be the only way to avoid washing out the subject even at minimum flash intensity. In summary thank you all for weighing in, as usual you all tried to come to my rescue by offering shooting advice, so kind <3 I think I am starting to put together a decent catalog of work, and indeed with flash. I have 5 User Modes and I use them all. I have some bound for Av functions, some Manual and I tend to visit X Mode a lot. I choose different modes depending on the situation you find yourself in. I am not bound to Av mode! Every shot taken in this series where flash was used (25/27 shots) was taken in X Mode or Manual! So please don't freak out when you see Av and P-TTL and this combo in the hands of Bruce (typically a recipe for disaster ), I am just exploring and studying what is happening, not advocating. In the past (when I knew much less) I had done events such as wedding receptions (moving from one well lit place and panning to another darker place) or other scenarios where some flash fill is welcome (bright harsh sunny skies), I had actually used flash with Av with little to no problems (no wildly odd exposures). Of course I didn't realise back then that my settings may have being fudged a little pre and post shot (which is what this post is all about). But to continue to insist that regardless of the scenario you find yourself in, to use little to no automation and always be fully manual is not always the best advice or strategy. The further you stray away from Automation the more time it takes your eye and skill away from the scene, your mind now has to deal with all the manual variables and in doing so can cost you the shot, it's as simple as that! If you have never found yourself in those kind of shooting conditions then good on ya! But make no mistake, it exists, we cannot control everything and be one step ahead of the light in the shot, that is why Av and other modes were created in the first place, to allow the user to get the shot assisted where otherwise too much fiddling would result in the moment gone. Please note once again the album I linked above with all those cosplay shots, this was not an example of one one those moments, I had time. I would argue that a few of you perhaps have not shot in hectic conditions or times when flash would assist in the shot but you need your camera up and firing in a matter of milliseconds or you've lost the moment! I'd rather chance something to letting automation do it's thing vs a completely ruined shot because I was in Manual Mode and my shutter speed woefully incorrect and just did not have time to adjust or (forget to) green button. Even if the mix of ambient light and flash is not the ideal balance due to using P-TTL and Av for example, if shooting RAW we have a lot of control to fix a lot of that stuff in post. What we can't fix is a completely blown out shot. Now I know the response to that is 'git gud' lol, but really I think a good photographer is someone who understands the advantages of certain modes and is willing to accept the chances of the disadvantages of that mode backfiring on them. It's a gamble. What we never discuss or hear here is that Manual Mode also backfires on the user, all the time! A recent visit to the zoo sporting a K200/4 meant Manual Mode all the way (no flash), and of course I have a mode set up for that, ISO 800 and I adjust the aperture of the lens to what I want and always green button before taking the shot. Even in casual 'all the time in the world' scenarios like this I forgot to green button (Tv Shift) before the shot and got a bad one. Concentration slip etc, it happens, even to the best of us. Not all shooting conditions give time and we must use all the tools available to us with the equipment we have. I repeat... I am not advocating Av + P-TTL but some indeed are and can produce exceptional fine work with it | |
03-13-2019, 03:08 PM - 1 Like | #15 |
.... Bruce, be fair please, this is what you told us in your first post, so I think we should be forgiven for understanding you are trying to use Av with Auto-ISO. You may have said you had changed it later, but the posts are quite long, so its likely that people are responding to the opening one primarily. No one is denying that its not possible to get some good flash shots using Av with P-TTL modes .... I use that sometimes myself too. But I agree with Steve that it is more suited to "snapshots" .... it is not suited to any situation where we need to take full control over the mix of ambient and flash brightness that is recorded. Whether results in dynamic situations using Av / P-TTL can be more than snapshots really depends on the skill and creativity of the photographer I feel. Don't forget to check out the impact of the Camera Flash Modes, which can have a major influence on the amount of ambient light allowed to be recorded. You asked about why the Auto ISO figure was not displayed prior to taking flash pics .... well, its because the figure is not calculated until the pre-flash. And there will be different decisions made based on a range of factors .... camera flash mode, focal length, amount of ambient light are a few of them. | |
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