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Photo Forum / Digital Photography / DSLR Cameras / July 2005Need help with some basics ...
Hi all, Being new to DSLR photography I'd like to think that I'm slowly coming to terms with the basics, but playing with my 350D tonight I've come across something I don't understand. Can someone help me out here? ... If I set the camera to FULL AUTO and take a picture across the room the flash pops up and the camera selects 1/60 Sec - F4.0 - ISO400 - no probs there. On PROGRAM Mode - same parameters. On SHUTTER PRIORITY however, with 1/60 - ISO 400 set the Aperature indicator is flashing to say "out of range" (it's only an F4.0 lens), and I have to come down to 1/30 of a sec to keep it happy (flash is primed for all of these tests by the way). On APERATURE PRIORITY it again wants a shutter speed of 1/30 Sec for correct exposure. So ... With ISO set to 400 for all tests and flash primed, WHY is the camera happy with an 1/60 + F4.0 combo on AUTO or PROGRAM modes, but insisting on 1/30 + F4.0 in Tv or Av modes? I don't get it. Any help apreciated. Many thanks, CC > On SHUTTER PRIORITY however, with 1/60 - ISO 400 set the Aperature > indicator > is flashing to say "out of range" (it's only an F4.0 lens), and I have to > come down to 1/30 of a sec to keep it happy (flash is primed for all of > these tests by the way). It's warning you that you need more aperture, it obviously needs f2.8 which isn't available on your lens. basically it's metering without compensating for the flash and telling you it's too dark. > On APERATURE PRIORITY it again wants a shutter speed of 1/30 Sec for > correct exposure. As above > So ... > > With ISO set to 400 for all tests and flash primed, WHY is the camera > happy with an 1/60 + F4.0 combo on AUTO or PROGRAM modes, but insisting on > 1/30 + F4.0 in Tv or Av modes? Presumably in AUTO it knows it's going to use flash. Sounds like the camera needs a bit more logic to tell it you are going to use flash. My 10D is identical. > It's warning you that you need more aperture, it obviously needs f2.8 > which isn't available on your lens. > basically it's metering without compensating for the flash and telling you > it's too dark. I doubt that it's not considering the flash because in addition to the flash being primed, it's also showing the flash symbol in the view finder. > Presumably in AUTO it knows it's going to use flash. Not quite I don't think - in AUTO it'll raise and fire the flash as/when required - in other modes it has to be manually deployed - but should still be considered when it IS manually deployed. With some further testing, I think the issue is to do with with AUTO exposure - I did a series of tests - on AUTO it seems under-exposed, whereas at 1/15 everything looks a lot brighter (and more correctly exposed). Does anyone know of an issue where AUTO or PROGRAM modes under-expose? >> It's warning you that you need more aperture, it obviously needs f2.8 >> which isn't available on your lens. [quoted text clipped - 3 lines] > I doubt that it's not considering the flash because in addition to the > flash being primed, it's also showing the flash symbol in the view finder. On my 10D deploying or not deploying the flash makes no difference to the meter reading, apart form the flash symbol, so where's it considering it ? > On my 10D deploying or not deploying the flash makes no difference to the > meter reading, apart form the flash symbol, so where's it considering it ? Good point. I'm left with the feeling that this is either a major bug, or I'm just not understanding how it's supposed to work. > > On my 10D deploying or not deploying the flash makes no difference to the > > meter reading, apart form the flash symbol, so where's it considering it ? > > Good point. I'm left with the feeling that this is either a major bug, or > I'm just not understanding how it's supposed to work. No bug. Read the book. Colin > No bug. Read the book. I did - it didn't help. I think that you need a certain basic level of knowledge before a lot of things in the book make sense - I'm not at that point just yet, although I'm learning quickly. >>It's warning you that you need more aperture, it obviously needs f2.8 >>which isn't available on your lens. [quoted text clipped - 15 lines] > > Does anyone know of an issue where AUTO or PROGRAM modes under-expose? Common problem with these cameras. Even some dedicated Speedlights will underexpose. Take to camera back to Canon and ask them to adjust the flash exposure. It's a warranty repair and fairly quick to do.  SignatureMessage authored by Douglas Who has Zero Care Factor about negative responses from anonymous posters. I do not consider mine (350D) underexposed. Mike Bernstein >>>It's warning you that you need more aperture, it obviously needs f2.8 >>>which isn't available on your lens. [quoted text clipped - 21 lines] > underexpose. Take to camera back to Canon and ask them to adjust the flash > exposure. It's a warranty repair and fairly quick to do. >> It's warning you that you need more aperture, it obviously needs f2.8 >> which isn't available on your lens. [quoted text clipped - 3 lines] >I doubt that it's not considering the flash because in addition to the flash >being primed, it's also showing the flash symbol in the view finder. That proves nothing. Both my 10D and 20D ignore the fact that the flash is going to fire in Av and Tv modes, when choosing the floating parameter. Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< > > It's warning you that you need more aperture, it obviously needs f2.8 > > which isn't available on your lens. [quoted text clipped - 15 lines] > > Does anyone know of an issue where AUTO or PROGRAM modes under-expose? In Av or Tv mode, the camera will attempt to expose for the ambient light, whereas in auto or P mode it only exposes for the flash. The typical use for Av or Tv is outdoor exposures in dull light or at night where you want to capture some of the background. The manual should go into this for you. Colin Herewith the section from the 350D manual. I do not personally think the manual deals with this quite as described in this group, although the last paragraph may have something to do with it. "P: For fully automatic flash photography. The shutter speed (1/60 sec. - 1/200 sec.) and aperture value are set automatically, just as in <1> (Full Auto) mode. Tv: Enables you to set the desired shutter speed (30 sec. - 1/200 sec.). The camera then automatically sets the flash aperture value to obtain the proper exposure at the shutter speed you have set. Av: Enables you to set the desired aperture value. The camera then automatically sets the shutter speed (30 sec. - 1/200 sec.) to obtain the proper exposure at the aperture you have set. Against dark backgrounds such as the night scenes, slow-sync shooting will be set so that both the subject and background are exposed correctly. The main subject is exposed with the flash, and the background is exposured with a slow shutter speed. Because automatic slow-sync shooting uses a slow shutter speed, always use a tripod. If you do not want a slow shutter speed to be set, set C.Fn-3 [Flash sync. speed in Av mode] to [1: 1/200sec. (fixed)]." Mike Bernstein >> > It's warning you that you need more aperture, it obviously needs f2.8 >> > which isn't available on your lens. [quoted text clipped - 26 lines] > into this for you. > Colin My point exactly - to me it only implies what it does - the reader has to draw a conclusion (which was beyond me at that point in time). > Herewith the section from the 350D manual. I do not personally think the > manual deals with this quite as described in this group, although the last [quoted text clipped - 54 lines] > > into this for you. > > Colin This is indeed odd. I have tried this on my 350D at ISO 200 and with flash raised (and registered in the viewfinder) in all cases: In P mode: 1/60, f4 In Tv mode: 1/60 set, f4 flashing but taken anyway. Exposure on the result identical to P mode. In Av mode: f4 set, camera set and took at 1/6! Over exposure on the result. I do not have an answer but at least we are all have the same issue. Mike Bernstein >> On SHUTTER PRIORITY however, with 1/60 - ISO 400 set the Aperature >> indicator [quoted text clipped - 22 lines] > use flash. > My 10D is identical. >basically it's metering without compensating for the flash and telling you >it's too dark. So what's to be done about it? I can't imagine that putting a Canon flash on a Canon camera takes us back to the days of manual exposure. With the flash engaged, which it will do automatically in full auto or if you manually engage it in P mode, the camera thinks that the flash will be the main source of light and takes over setting the exposure. However, in Tv, Av, or M mode the camera thinks the flash will be used only for fill and takes its exposure settings from available light then adjusts the flash duration for the amount of dialed-in fill. > Hi all, > [quoted text clipped - 31 lines] > > CC Thanks David, I think you've hit the nail on the head. Is there any resource that you can point me to that would give me more info on this? (I couldn't immediately see the answers in the user manual) Thanks, CC > With the flash engaged, which it will do automatically in full auto or if > you manually engage it in P mode, the camera thinks that the flash will be > the main source of light and takes over setting the exposure. However, in > Tv, Av, or M mode the camera thinks the flash will be used only for fill and > takes its exposure settings from available light then adjusts the flash > duration for the amount of dialed-in fill. Don't know if it's still active but try -- http://teladesign.com/photo/eos-flash/ > Thanks David, > [quoted text clipped - 17 lines] >> takes its exposure settings from available light then adjusts the flash >> duration for the amount of dialed-in fill. It's working a treat - thanks for that - I think it's going to cover EVERYTHING I need to know for now (and some time to come!) Cheers, CC > Don't know if it's still active but try -- > [quoted text clipped - 21 lines] > >> takes its exposure settings from available light then adjusts the flash > >> duration for the amount of dialed-in fill. David wrote: >in Tv, Av, or M mode the camera thinks the flash will be used only for fill and he and Justin are the only correct respondents!! I don't own a Canon, but this is a pretty basic concept and I would be very surprised if other DSLR's didn't act similarly. My prosumer does it too, and *so it should*.. I stand a suitably humbled man - on the upside, that's about 3 things I've learned from the group already :) ... at least I've heard of the term "fill in flash"! > David wrote: > [quoted text clipped - 4 lines] > if other DSLR's didn't act similarly. My prosumer does it too, and *so > it should*.. >I stand a suitably humbled man - on the upside, >that's about 3 things I've learned from the group already :) I wasn't intending to humble you, but I was a little surprised at some of the replies! So to summarise - as soon as you step into A and S modes, the camera should (and obviously did) go into 'you're the boss' mode, along with 'meter the scene only' mode. In P and Auto modes, it pretty much assumes you're a dummy, and you just want the camera to give you a well-lit exposure. So if it thinks the scene is too dim for a hand-held shot, it decides to do the whole lighting thing itself with the flash as the light source. In A and S (or Av and Tv) modes, it just meters the scene and assumes you know what you are doing - and if the flash is up/on, the camera logic will dial it down to just *fill* the exposure. Which is all probably *exactly* what you want..! <snip> > In P and Auto modes, it pretty much assumes you're a dummy, and you > just want the camera to give you a well-lit exposure. So if it thinks > the scene is too dim for a hand-held shot, it decides to do the whole > lighting thing itself with the flash as the light source. Not quite right, there. In 'P' mode, the camera will attempt to calculate the correct exposure, and if the light is too dull, the camera will set the aperture or shutter readout in the VF flashing to indicate that there is insufficient light. In 'P' mode - or indeed any of the 'creative' modes - the flash will not automatically pop up as it does in the auto modes. If you want it, you have to press the button to elevate the flash to activate it. > In A and S (or Av and Tv) modes, it just meters the scene and assumes > you know what you are doing - and if the flash is up/on, the camera > logic will dial it down to just *fill* the exposure. > >Yep. Catches some people by surprise when they try to choose a smaller aperture with Av, whereupon the camera gives a loooong exposure. Colin |
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