Saturday, 10 January 2009

Wedding Photography Kent - Manual Mode

For further photography-related information check out my compendium of tips.

If you struggle to understand what follows, I'd recommend you read the post on metering and exposure.

Exposure is determined by incident light. Cameras, however, measure reflected light. Therefore, to estimate the incident light from the reflected light measurement, cameras assume that a scene has an overall reflectance of 18% (equivalent to a tonality termed middle grey). In most cases this works very well, but when the overall tonality of a scene is not middle grey, a situation which occurs frequently at weddings, exposure inaccuracies result. Exposure compensation is one way of correcting for this and is a technique that photographers need to be familiar with. Under the correct circumstances though, an alternative approach is possible - using the manual mode of your camera.

Let's say you're shooting outside at a wedding reception. All the guests are standing in open ground, not shaded by trees or buildings. It's a lovely sunny day and there are no clouds in the sky. In this case all of the guests are being lit by the same amount of incident light and the exposure settings will therefore be identical for any shot you take under these conditions. Once you've found an exposure that you're happy with, using the camera's reflected-light meter and by checking the histogram, you can put these settings into your camera's manual mode and shoot away without worrying whether a scene's reflectance deviates from middle grey. If you keep an eye on your camera's light meter, you'll notice that when taking shots of the bride in her white dress the camera will think you're overexposing (which would have resulted in underexposure if left in an automatic mode such as aperture priority, requiring positive exposure compensation) and that with the groom in his dark suit the camera will think you're underexposing. You know, however, that your exposure is spot on and that it's the camera's reflected-light meter being fooled. If you do this, don't forget to regularly review your exposures, just in case a cloud has crept in front of the sun and reduced the amount of incident light!

Manual mode is also extremely useful when shooting indoors in low light. Let's say, for example, that the maximum ISO setting you're prepared to use on your camera is 1600, that the minimum shutter speed you're prepared to use when shooting people is 1/60 sec, and that the maximum aperture of your lens is f/2.8. These personal criteria determine the maximum amount of ambient light that you can capture.

Let's say you're in a dark wedding reception venue. To correctly expose for ambient light requires an exposure of 1/15 sec at f/2.8 and ISO 1600 - 2-stops lower than your exposure criteria. What you can do in this situation is to dial 1/60 sec, f/2.8, ISO 1600 into manual mode, underexposing for the ambient light, and then use flash to illuminate your subjects. You'll be capturing the maximum amount of ambient light allowed by your exposure criteria and not allowing your camera to give an unusably slow shutter speed, which would occur if it tried to correctly expose for ambient light.

manual, 1/50, f/2.8, ISO 1600, 0 EV, -1 FEC, 35mm

If you've not done this before you'll probably be surprised to see how much detail you capture in the background with this amount of underexposure. The image above was taken using this approach and the background is over two stops underexposed (and I've added a vignette).

1/25, f/2.8, ISO 6400, +1 EV, 16mm

If you have a DSLR which performs well at high ISO, and you're happy to use these settings, then you can expose correctly for just ambient light in very low light settings. Check out the shot above taken with a Canon EOS 5D Mark II.

Check out more of my photography here: wedding photographer Kent


Richard said...

That's a good explanation. What's the limitation of just using manual mode all the time then?

Thank you

David said...

Hi Richard,

The key point about the above two situations is that your exposure settings remain constant. If they're changing for each shot you take it's much faster to put your camera into an automatic mode and then exposure compensate - there's nothing to be gained by using manual mode.



Pat said...

Good article David introducing the idea of reflected Vs. incidence metering.

To add to your article if readers are to competently use their meter to accurately recreate the tones they will also need to test the accuracy of their camera's meter. This can be done by comparing your incidence and reflected readings against something known to be 18% grey.

Most digital camera meters underexpose between 0.5 and a full 1 stop.

Another caveat to bear in mind when using the histogram is that it gives you an RGB presentation. If you're shooting RAW there will be extra head room that can be retrieved in applications like Lightroom.

Totally agree with you on using the camera in manual mode. I used that in weddings all last year with spot metering and the quality of my pictures has improved greatly. I have found spot metering can be more fiddly so will try centre weighted for pictures taking in more of the scene opposed to close ups.

Understand your camera's exposure metering and take control with manual control where practical.

A Newbie (Christian) said...

Hi David,

If I want to shoot people dancing in low light. I would guess that with a fast lens, say 35L, that at F1.4 the point of focus is so narrow that any movement of subject would result in an out of focus image. It's not going to work without flash and so a high shutter right? Can any lens freeze action in low light while exposing ambient light?

I'm not clear also on the effects of wide apperture used at a distance, say in group shot. For example an 85L used for a facial close-up at F1.2, has such a small area in focus - does it apply if the same stop is used for a group shot?

Sorry if this is a silly question!

David said...

Hi Christian,

It's only by asking questions that we learn!

Your two questions are both related to the concept of depth of field (DOF). As you rightly point out, DOF depends upon lens aperture and distance to subject. The wider the aperture and the smaller the distance, the lower the DOF is. I would urge you to experiment with your camera to build up an ability to judge DOF.

It is possible to freeze action, such as dancing, in low light without flash. Typically I'd use f/2.8 and ISO 3200 (or ISO 6400 with my new 5D Mark II). You can use wider apertures but will need to be further from your subjects to keep them fully in focus.

I've never shot a group at f/1.2. It is possible in principle but would very much depend upon how 'deep' the group is, plus you'd need to stay quite far away!

When shooting groups I prefer to stay above f/4 but I have had to use f/2.8 when illuminating big groups with flash in dark rooms.

Hope this helps.



Duncan Astbury said...

How do manage noise at the higher ISOs? I have recently had a 5D mk II, great camera but when I did a series of test shots at different ISOs I could clearly see noise (noticeable in blocks of even colour) from ISO 400 up. I am used to shooting for stock at ISO 100 so am I being overly picky? I shoot RAW and process through Lightroom v2.2. I understand the on camera noise reduction only applies to JPEGs. What should I be doing to get good photos at ISO 800 and up?

David said...

Hi Duncan,

If you're used to shooting at ISO 100 then you'll find the noise quite offputting at high ISO. The 5D Mark II is about as good as it gets for low noise due to its large sensor - you should try using a compact at high ISO!

For cleaning up images I highly recommend NeatImage - an amazing piece of software!



Brian Silver said...

On my 5D Mk2 I notice that the metering is not equal between AV and Manual modes - do you see this too?
So if aperture shutter speed, metering mode ISO etc is all identical, and I meter a scene in Manual mode to get the EV at 0 - this creates a fine exposed image. If I then dial in the exact same settings into AV mode the EV requires +1 to match the same exposure of manual mode. Why is this?

This suggests to me that AV mode always underexposes.

Thank you

David said...

Hi Brian,

I assume you mean the other way round - you meter in Av mode and then plug these settings into manual mode?

I've just compared exposures between Av and manual modes and they are identical, as they ought to be.

I can think of only two reasons that they might be different:

1. You've got exposure compensation set in Av mode.
2. There's a problem with your camera.

Please let me know how you get on.



Brian Silva said...

Hi David,

I have indentical metering when not using the Speedlite. If the Speedlite is on with ETTL, then the same settings for shutter, aperture, etc give a different exposure. I need to dial in EV+1 under AV mode to see the same histogam under M mode.

Maybe I'm doing something wrong, but this is the 580EXII making the difference.

Is my understanding of EV wrong, in manual mode a set my iso, shutter, aperture etc, press half-way to see the reading and turn the dial to get the EV metering at 0 - this results in a balanced exposure BEFORE I take the shot. In AV mode I'm not able to see if my exposure is near the mark until AFTER I take the pic.

Confused now :)

David said...

Hi Brian,

You didn't mention you were using a Speedlite in your original post - that makes all the difference.

E-TTL is an algorithm for balancing ambient and flash light. Canon have published some limited information on how it works - search my blog for E-TTL. It often underexposes for ambient light and uses the flash light to fill in and, as a result, the ambient light exposure will be different to that which you see in manual mode.

In manual mode the camera is looking at ambient light only - no E-TTL algorithm is being applied to metering.

Does that help?

You've lost me with your second paragraph though!



Brian Silva said...

Aha - I did not realise Manual Mode did not factor in ETTL. Sorry I forget to mention the flash in original post.

My second paragraph. All I'm trying to explain is that in AV mode the EV meter does not move around so I need more guess work to judge if the shot will be over or under exposed. In Manual mode the EV meter is helping me along.

Many thanks - Great blog, I like the educational aspect.

David said...

Hi Brian,

The exposure level indicator (which you can see in the LCD panel and in the viewfinder) is helping you in both Av and manual modes.

In Av mode the camera will determine an exposure based upon a reading from its internal reflected light meter and, by default, is set to no exposure compensation (the indicator will read 0 and, as you point out, does not move around if you change the aperture - it adjusts to give you what it thinks is the correct exposure). To adjust this, which you'll need to do for many of your shots since the camera's meter is so easily fooled (search for exposure compensation on the blog), you use the Quick Control Dial on the back of the camera, and you'll see the indicator can be moved within a range of +/- 2 stops.

With manual mode you're free to stray outside of this +/- 2 stop range, but the camera is still using its internal reflected light meter to determine whether you are under- or overexposed with your current settings.

In both cases you still need to have a scan of your shot and its histogram to determine if your exposure was accurate.