Why are my exposures all over the place?

My brand new speedlight let me down last May when taking two quick photos of graduating students at our university. I have to fire two shots – boom, boom - of each graduate receiving their diploma from the President. The speedlight heated up and slowed way down – before 40 shots! Not good in an auditorium full of people and a line of smiling students. The backup flash helped save the day.

This year, after doing much research, I rented a Qflash TRIO for my camera and the Turbo 3 battery pack. This was my first time using this system and I only had a short time to try to "get it right" before the big day. I must have missed something as my light output was all over the place. Thankfully in Lightroom, and Photoshop CS4, I was able to get a usable photo.

In reading the instruction booklet I saw how not to use the P (Program) mode because it will cause inconsistent outputs). So I used the Shutter Priority and the Aperture Priority modes. No matter which I switched to, nor the changing of shutter speed, or aperture, and ISO, the results were about the same. First photo was the better lighting exposure but the second one – taking right on the heels of the first – would be overexposed. This happened almost every time.

Once out of the dimly lit room, and into the sunlight, I changed shutter speed and ISO and the photos – still using the QTTL mode for fill light – were better in the bright light. I was using the evaluative metering setting for all photos.

So, what did I do wrong? Why such a wide range of exposures? It seems like what I pictured from what was described as would happen using P (Program) mode – inconsistent outputs.

Other than that exposure all-over-the-board problem this system never missed a beat. No slowdown, no overheating. It was there for me each and every time I pressed the shutter. I loved that part.
1 person has
this question
+1
Reply
  • First, you were indoors and shooting TTL metering. You were using evaluative metering. This means that what ever you were pointed at could cause shifts in exposures. The colors of the gown, the people and the background all combine to determine the exposure. We usually recommend to use spot metering to take the background out of the equation. This will get you better exposures because you are not taking in the background, which if dark can make your images overexposed because the camera is trying to make it brighter, thereby over-exposing the subjects that are closer.

    Second, when shooting indoors, it will be better to use the Qflash in Auto-Fill Mode. The sensor on the Qflash will control the flash exposure instead of the camera body. The Qflash sensor sees the scene as an out-of-focus gray haze, rather then sharp tonal values. You can also set a given distance on the sensor. It will generate enough light to reach the distance you set at the ISO and f/stop you have set on the camera. It helps to keep the background from affecting the exposure.This leads to more accurate and more consistent exposures.

    Third, You were using the camera in Aperture Priority and Shutter Priority. These still use the TTL Evaluative or Matrix metering from the camera body. Indoors, it is advisable to use the camera in Manual Mode, with 1/60th @ f/5.6 with ISO 400 one of the most commonly used exposures. You should get very repeatable results, shot after shot.

    Fourth, you were getting a consistent over-exposure on the second shot time after time. There is a possibility that there may have beef a flash or camera exposure bracketing set on the camera. I think this may be the cause due to you getting a normal exposure then an over-exposure repeatedly, time after time.

    Fifth, something not mentioned but to be considered. Do not use Auto ISO setting on camera, since the meter is still active in Manual Mode and it may be changing the ISO on you.

    Sixth, TTL Full Matrix or Evaluative Metering does work better outdoors, where the light levels are brighter and the background is not as dark.
  • (some HTML allowed)
    How does this make you feel?
    Add Image
    I'm

    e.g. kidding, amused, unsure, silly indifferent, undecided, unconcerned sad, anxious, confused, frustrated happy, confident, thankful, excited