Sunday, 4 February 2018

Keep it Simple: Fill in Flash in harsh daylight

It's not hard to reduce shadows in harsh daylight, for general circumstances. Here's how.

Equipment used:
  • Olympus OM-D E-M1 Mark 1
  • Nissin i40 (for MFT cameras, able to support TTL and HSS)
Many people who eschew using flash, are used to P A or S (Program vs Aperture Priority vs Shutter Speed priority) for ambient light shooting. P A or S can be so convenient, you feel like using it all the time. When you fit the flash on, you want the flash to somehow work in with the situation. It seems natural to think like that. 

P A or S were designed for when the camera just measures the light in the scene, computes what ISO / Aperture / Shutter Speed is right to use. When you introduce the factor of Flash, the camera now has a conundrum - the flash will only show its hand when it fires, not during liveview before you press the shutter release. So the liveview estimates for ISO / Aperture / Shutter Speed may or may not be able to be fulfilled when you click.  In this case, the camera makers so far, have made assumptions on how to make this mechanism work for P A S. These assumptions may set limits on what you want to do and you may spend more time fighting these assumptions than making forward progress.

Do the Gordian Knot thing - take a deep breath and leave P A S alone. For this situation, use Manual Exposure on the camera body and take control of your destiny.
  1. Switch to Manual Exposure on the Camera
  2. Ensure Liveview Boost (on Olympus cameras, the jargon is different for other mirrorless cameras) is set to OFF so that Liveview will emulate the exposure if using ambient light alone - this is typically OFF under normal use.
  3. Ensure that you are not using Silent Shutter.
  4. Set the ISO to fixed ISO 200
  5. Set the shutter speed to 1/250th sec
  6. Set the f/no to f/5.6
  7. Have look at Liveview, take a shot. Make it look reasonable - darken / brighten by changing the f/no but keep the shutter speed at or below 1/250th sec.  This is what I got:
In this photo, without flash, I've adjusted the settings so that the brighter leaves are pleasant but the leaves in shadow are a little dark
  1. Now fit the flash, switch it on, ensure the flash is set to TTL Auto (on the Nissin i40, there are two choices on the flash dial - "A" for standard TTL Auto and "TTL" if you want to use an enhanced mode and adjust flash brightness compensation using the dials on the Nissin i40 - choose A)
  2.  and ensure that the camera has the flash icon in Super Control Panel enabled. Simply point the camera at anything (not your eyes) and click just to check that the flash will fire when you click.
  3. Take a photo with the flash thus ready.
Photo with flash on TTL auto but otherwise same settings as the previous image above.
Notice in this photo, the shadows have been lightened considerably. You can now change the f/no by a little bit if you want to tweak to taste.

If the ambient light changes considerably, you might want to adjust the f/no again but I'm assuming you're using this technique because it is constantly bright and harsh and the lighting is not volatile.

If you are happy with this look, that's it, no need to read anymore. 

For those who are looking for more blur in the background and they have a lens that opens to f/2 (or brighter) which allows a shallower depth of field, this is what you do next.
  1. Fit the brighter lens, take off the flash or disable the flash from triggering.
  2. Ensure the lens is set to f/2 or the bright aperture that you so desire. Take a shot without the flash.  ISO 200, 1/250th sec, camera on Manual Exposure. This is what you get:
Over bright exposure, with a bright f/2 lens, same ambient lighting as the previous photos
So you see, by ambient light itself without flash, the exposure is too bright. Using Liveview, you will want to adjust the shutter speed so that the photo does not bleach out. This makes a high shutter speed necessary. 
  1. Take another shot, adjust the shutter speed faster so that the photo without flash looks nice enough. Let us say, I got a photo that was nice at 1/800th sec.
  2. Fit the flash, enable the flash in the camera. You will see the shutter speed drop to 1/250th and no amount of camera dial twirling will make it rise. This is the stage when you want to enable High Speed Sync (HSS).
  3. On the Nissin i40 (see pdf manual), you enable HSS by pressing the lighted green button on the flash for a few seconds until a white LED blinks near the right-hand dial on the flash. Once you see that blink, you can use the camera dial to raise the camera's shutter speed past 1/250th sec. So raise the camera's shutter speed to the shutter speed that you arrived at in step 13.
  4. Take the shot with the flash firing. You'll get this:
So, a similarly pleasant shot as the one you got at f/5.6 with flash. 
This new shot is similar in exposure brightness to the one you got at f/5.6 with flash. However, this is at f/2 or brighter and you now have a blurred background.

That's it. You've survived Manual Exposure on the camera body with TTL Auto and HSS on the flash and used a bright aperture like f/2 for shallow depth of field bokeliciousness.

Like what you read? Learnt something from it?

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I have other flash notes too.

MFTMicro Four Thirds mirrorless cameras. These cameras have LiveView so that you can see what image will look like in ambient light before you click
TTL FlashThrough The Lens metering so that the camera can measure the light that the flash
produces when the flash triggers and regulate it to the image brightness you have nominated HSS
HSSHigh Speed Sync - Focal Plane Shutters have a limited maximum speed when used with flash (flash sync speed), typically 1/250th sec and in bright sun outdoors, you need a higher speed than that. So HSS (also called FP mode) was invented to pulse the flash light many many times during the exposure so that the camera body allows you to use a higher shutter speed than the flash sync speed
Focal Plane ShutterThere are several types of shutter used in the variety of cameras. DSLRs and interchangeable lens mirrorless cameras tend to use a Focal Plane Shutter. A Focal Plane Shutter at a shutter speed higher than Flash Sync Speed, produces a travelling slit to expose the sensor that is less than the full area of the sensor.

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