PPlease can anybody offer some advice.I use a EOS1N with 540 flash,My main problem has been under exposed photos.I have to use the flash on +2 flash compensation which gives me good results,the problem is I loose distance.The same problem occurs when I use 28-70 or any other lens.Fill flash works OK but its when I use it as the main light source and I set the camera too M and the shutter speed too 200.The distance scale can be read off the flash,most of my pictures are taken within 7m,well within the flash distance scale on the gun. Thankyou for your response Robin Bush.

-- Robin Bush (karen.mccarthy@xtra.co.nz), March 06, 2000

Answers

Are they ALL underexposed? Do you use print film? Could it be the printer?

-- Jim Strutz (jimstrutz@juno.com), March 07, 2000.

Robin emailed and said it's all slide film, so I don't have any idea here. Anybody else got one?

-- Jim Strutz (jimstrutz@juno.com), March 07, 2000.

It is possible to set flash compensation on both the flash AND the camera. When both are set to compensate, the flash has priority and overrides the camera settings. Is this a cause?

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-- (John.MacPherson@btinternet.com), March 08, 2000.

I have had underexposure problems also, using an EOS-3 and 550EX. It is an intermittent problem, which I haven't solved yet. It is frequent enough to be quite bothersome. I shoot print film, and use the flash as the primary light source. I shoot at ranges well within the range indicated on the unit (3-5m usually) with a 28-135 lens. I use the camera in M mode, which, theoretically should cause the flash to use pre-flash information to regulate the amount of light for a correct exposure. I usually use F 5.6 - F 8 with a shutter speed of 90 - 180.

I am going to start a process of elimination to determine what the problem is. My first guess is that I am inadvertantly asking the camera to gather exposure information from a white subject - thereby creating a grey-scale related underexposure. This may be either: a). operator error, by poor focusing point selection b). operator error in conjunction with CF-13 selection, c). operator error in conjunction with metering mode selection, d). camera evaluative metering software bug, or e). some combination of the above.

Does anybody have any suggestions as to how to solve this problem, or at least work around it. It would be greatly appreciated.

Geoff

-- Geoff Mann (geoffman@direct.ca), March 11, 2000.

Geoff: Have you tried A/B comparisons in which you alternate between M and one of the auto modes such as P, Av, or Tv? If, in one of these auto-modes, the pictures are consistently well exposed, then I would be suspicious that, in M mode, you might be choosing too small an aperture and/or too fast a shutter speed. I'm too lazy to go find my owner's manual, but off-hand I would think that you should carefully review how the flash interacts with the camera in manual mode, especially any instructions or comments relating to the flash's handy "coupling range" indicator scale while in the camera's M mode. FWIW, with my 540EZ and 1n (my new 550EX is sitting in my closet, waiting for an ordered 1V to arrive...), I occasionally encountered problems similar to yours until I soon figured out that I was sometimes inadvertently not shoving the flash foot all the way into the camera's hot shoe. When this was the case, the clues that tipped me off were 1) the locking pin dial felt snug after too few turns; 2) the flash would often fire with shutter release, BUT a check of the flash's LCD might show that the flash was not registering the focal length of the lens currently on the camera (or zoom position if a zoom was in use), but instead the flash might display the focal length of the last lens it encountered when it was correctly coupled to the hotshoe. In this case, the coupling range scale may be inaccurate, and because there is not a full connection, TTL may not be in effect, or flash firing may not be truly synchronized with the shutter, and the flash pop may be nothing more than a sort of misguided test pop. So...I would suggest testing for the soundness of the hotshoe connection by 1) varying aperture or shutter speed to see if the coupling range scale changes accordingly, and also making sure the flash recognizes different lens lengths, as well as checking to see if the exposure confirmation lamp briefly glows green after the shot is taken. At least in my experience with the 540EZ and an A2 or 1n, operator error was the usual culprit.

-- kurt heintzelman (heintzelman.1@osu.edu), March 11, 2000.

Thanks Kurt:

No, I haven't tried A/B comparisons in which I alternate between M and one of the auto modes such as P, Av, or Tv, although I am seriously considering it. As you know, the 550EX is an expensive piece of equipment, and I like the promise of using creative options associated with using it with the camera in M mode. If I use Av, I give up control over the shutter speed, and if I use Tv, I give up control over depth of field. In P mode, I give up both. My first priority is to try to figure out why M mode isn't working to my satisfaction. If it isn't, I'll send it to a repair depot and/or complain to Canon. This is a pretty powerful flash, so I don't think it unreasonable to expect it to give sufficient light at F8 and 180 at 5 m distance with an ISO 200 print film. The "flash range" indicator on the unit says it is okay, so it should have enough power, otherwise I have a real problem (ie. can't trust the indicator)

Yes, I have reviewed the owner's manual repeatedly and I think that I understand how the flash interacts with the camera in manual mode. The pre-flash provides information to the camera, which then tells the flash how much power to use.

Yes, I too have figured out that I was sometimes inadvertently not shoving the flash foot all the way into the camera's hot shoe. Thanks for the tip about checking with the display to see that the hot-shoe was talking to the camera.

Do you know who I should talk to at Canon about this issue? It sounds like Robin may have a similar problem. Thank again.

Geoff

-- Geoff Mann (geoffman@direct.ca), March 11, 2000.

Another thought: When shooting in M mode, I first meter the scene with the ambient light, and then begin varying aperture, shutter speed, or both to arrive at a "correct" or "zeroed" exposure according to the camera's exposure scale (<---"0"+++>). In M mode, one is of course able to pick any allowable aperture and shutter speed, but are you first (using only the ambient light) finding this correct exposure for the ambient light, and are you then watching the exposure scale as you change aperture, shutter speed, or both, to see how many stops underexposed your final choices are (with the ambient light) when compared to this reference point? If one now adds a hotshoe flash with finite energy to the mix, I'm again wondering if the Inverse Square Law of Light isn't coming into play IF one selects too small an aperture, or too fast a shutter speed, or too fast a combination of the two--such that the flash can't deliver the goods. As I recall, the Inverse Square Law basically states that, for a CONSTANT aperture and shutter speed, the brightness of a point source of light drops off really fast (1/the square of the distance of the light source from the camera?). Therefore, could it be that you are mis-judging the light output of the hotshoe flash because seemingly small changes in aperture and/or shutter speed may be exponentially taxing the flash according to this law? --> Let's say that in M mode, before adding flash to the mix, your chosen aperture and shutter values are, say, -3 stops underexposed according to the camera's meter and exposure scale. If you now add the hotshoe flash, the Canon literature suggests that the metering systems for flash and existing light are independently controlled, and that M camera mode can be combined with fully automatic flash exposure, but it seems to me that the Inverse Square Law still prevails, and if you've chosen A and/or T values that are too fast, the flash can't deliver the goods, and therefore I again ask if the flash's exposure confirmation lamp is showing green after these shots. If it isn't, the flash is telling you the shots are under-exposed. If it IS showing green, then perhaps the camera's brain is (incorrectly?) telling the flash to quench itself at -3 stops...To test this, one could for example setup a scene that typifies your problem in M camera mode, set the FLASH to manual mode and at full power, and see what happens. (I'm not sure why the coupling range would show acceptable parameters, but I do wonder if the flash is monitoring only aperture rather than A and T values). This is a very interesting thread (like I said, I've got a 550EX sitting in my closet still in the box), and I look forward to following this discussion and learning from you all.

-- kurt heintzelman (heintzelman.1@osu.edu), March 12, 2000.

Yet another thought (!): With my 1n and 540EZ, when I've experimented with shooting scenes in very low ambient light with flash, and using Av or Tv, if I try to choose an aperture (or allowable shutter speed) that the camera thinks is too small (or too fast), that value will continuously blink to indicate that it is too fast. The manuals state that when this occurs, the background will be under-exposed, but the foreground main subject *MAY* be properly exposed...

-- kurt heintzelman (heintzelman.1@osu.edu), March 12, 2000.

I have been using a 1n/540 combo in manual with no hangups for several years now. Just a thought.....is your flash head tilted down? This will set you for closeup mode. I have never even thought to use it in Tv/Av or P mode. Dumb question, but are your batteries up to snuff? When I do weddings and the like, I go rent a power pack. Also, have you looked at the green confirmation light? If it lights and you are still getting underexposed looking prints, burn a roll of slide film trying every setting and control and keep careful records..

-- Leo (Leoticus@sd.quik.com), March 18, 2000.

Robin: In your e-mail to me you said that the problem occurs even with a borrowed 540 flash. Can you borrow another 1n to see if the problem lies in your 1n?

-- kurt heintzelman (heintzelman.1@osu.edu), March 22, 2000.

To Robin

I am baffled, just like yourself. I have the same equipment as you have. I recently purchased a brand new 1n and also have the same problem. I sent my 1n and 540 flash to Canon for testing. Their answer was "The factory default setting for flash TTL is one stop under exposed when used in M mode, and apart from that everything is working well!" So really I am afraid I have no answer. I still feel that there is a problem. It is a very uneasy feeling every time I head off on an assignment with exposure problems at the back of my mind. I hope we can get to the bottom of this problem. This is all I can tell you for now, but I am still in search of an answer. Thank you. Reinaldo.

-- Ren Guarnera (guarnera@one.net.au), April 20, 2000.

Ren: So why didn't Canon fix your flash? Did they merely diagnose and state the problem but then not fix it?

-- kurt heintzelman (heintzelman.1@osu.edu), April 20, 2000.