High ISO Noise Comparison

I have already talked a little about the effects of high ISO noise in a previous post. And one of the reasons I wanted to upgrade from my Canon EOS 300D to my new 30D was it's alleged better performance at high ISO settings, plus the ability to choose ISO 3200 in really dark situations, whereas the old camera would only go up to ISO 1600.

So I thought it might be useful to take a closer look at some photos taken with each camera, and see if things really are any better in dim conditions.

EOS 300D - Sigma 135-400mm EF f/4.5-f/5.6 - ISO 1600

Back in December 2005, I went to see Saracens play Wasps away in High Wycombe. It was a fairly late kickoff, and being December, it wasn't long before the floodlights were on and things were getting pretty dingy on the pitch. Here's a picture of ref Ashley Rowden supervising the scrum:

[The ref's head is highlighted above]

The picture doesn't look too bad resized for viewing on the web. But looking at it at full resolution, you'll see what happens:

[The highlighted section shown at Actual Pixels (100%) size]

You can see that the skin tones show noticeable coloured noise, and the black areas are also very mottled. The whole image is fairly soft and not very saturated.

EOS 30D - Canon 100-400mm EF L f/4.5-f/5.6 - ISO 1600 / ISO 3200 (HI)

Yesterday, I was back to see Saracens play Glasgow at home in Watford. Admittedly with a different lens, but it's the camera body itself which is the biggest factor in image quality in low light. By the second half, the floodlights were on again, and this is the first shot we'll look at taken at ISO 1600:

[The Scrum Half's head is the piece to be enlarged]

Again, the photo above is good quality at web resolution, but I think there's a definite improvement at full size:

[The second highlighted section shown at Actual Pixels (100%) size]

This time, the blacks are cleaner and there is less obtrusive coloured noise in the skin tones. It looks noticeably sharper, and the colours are more vivid.

Here's another one, as it was getting even darker. In order to keep the shutter speed up, the only option was to increase the ISO setting, since I was working at the lens' maximum aperture, f/5.6. So I used the ISO setting on HI - which basically means 3200:

[The Prop's head is the bit we're interested in]

I'm impressed with the web resolution image - certainly crisp, clean and good colours. And closeup?

[The third highlighted section shown at Actual Pixels (100%) size]

Pretty impressive! I'd say 3200 with the 30D looks better than 1600 with the 300D. So I reckon it's been a worthwhile upgrade for that alone. Plus the fact the 30D is much quicker a writing images to the Compact Flash card - vital when taking a sequence of high-speed action photos. With the old camera, I would often be left frustrated after following the action up the pitch - I'd miss a try because the camera was still unloading it's buffer to the card!

Needless to say, rugby in the dark days of winter push the capabilities of a camera quite hard. The speed of action and low light are both factors which probably won't bother you too much if you just take a few holiday snaps or family pictures with your SLR.

How To Take... Concert Photography

Novice photographers are often disappointed with the shots they get from their cameras at concerts and other low-light situations. This is usually due to the fact that, if left to it's own devices, the camera will decide what ISO speed to use, and can also insist on using on-camera flash.

If you're at a concert, using flash can be enough to get you thrown out of the venue (to say nothing of it being pretty rude going off in the artists' faces). It also results in very harsh, flat lighting, which completely drowns out any of the colourful stage lighting, ruining the atmosphere.

In order to capture the colours to full advantage, turn your camera to manual - or at least, alter the ISO-setting to the highest it will go - 800 or 1600 if possible, and turn off the flash. This should force the camera to choose a wide aperture and fastest shutter speed possible, which will help capture the colours and action on stage.

[The Rumble Strips - stage lighting effects are good to capture with the wide angle lens]

Venue:

Alexandra Palace, for a private gig by The Rumble Strips. Because it was a private show, photography was allowed, but this isn't always the case at concerts. I was right in the front row, so no-one's head was in my way!

Equipment:

• Canon EOS 30D set on ISO 1600 and Programme AE
• Canon 17-85mm f4-5.6 EF IS lens for wide shots
• Canon 75-300mm f4-5.6 EF IS lens for closeups/portraits

Portraits:

Try to get the musicians "doing something" or at least, appear to be in the middle of singing!

[Tom Garbutt on bass, with a green spotlight picking out some highlights]

[Henry Clark on trumpet, with a magenta spotlight backlighting]

If you can, try and fill the frame for some interesting shots of the instruments:

[Closeup of the poor old battered guitar Charlie was strumming]

It's always good to be right at the front of the crowd, to get the best pictures. And if you can turn off you flash and wind up the ISO sensitivity of your camera, you're likely to get more interesting pictures than the bloke next to you holding up a camera phone!

Putting It All Together - Exposure

Background
I've already explained the basics of ISO speed, apertures and shutter speeds. Now it's time to put them all together and see how they relate to the overall exposure of an image. The EV or Exposure Value for any given scene and lighting is always a constant.

Theory
The correct exposure for an image is governed by a complicated formula. However, all you really need to know is what effect altering any of the three options has on your pictures. So, for a particular scene and lighting conditions, your camera might suggest this exposure:

ISO 200, 1/250th @ f/5.6

If we were to change the ISO setting to 400, the film or sensor is now twice as "quick" at gathering the same amount of light, so the exposure time can be halved:

ISO 400, 1/500th @ f/5.6

Or, the same amount of light will be let in using 1/250th of a second as before, but decreasing the size of the aperture (increasing the f-number):

ISO 400, 1/250th @ f/8

Assuming we leave the ISO setting as it was originally, the following are also equivalent exposures to the first:

ISO 200, 1/125th @ f/8

ISO 200, 1/500th @ f/4

To see more equivalent values, you might like to look at this interactive EV calculator.

What does this mean for your pictures? Well basically, the combination of shutter speed, ISO and aperture is always a trade-off, depending on your priorities - or what you can change. Sometimes you may have low light and hit the widest aperture of your lens, which will give you slower shutter speeds. If you still want pictures which don't suffer from camera shake, you will need to increase the ISO setting.

Other times, you might have plenty of light (on a sunny day), so use a slow ISO setting, and choose the aperture/shutter speed to either freeze movement (fast shutter speed) or maximise depth of field (small aperture).

Examples
Here are some shots I took of the moon, in October 2004. With this sort of subject, you often don't know what will be the "correct" exposure, so by keeping two of the three parameters the same, and just changing the third, you can bracket the exposure to see which is best.

In this case, I used ISO 200 (to preserve fine detail) and the lens was set at it's widest aperture, f/5.6. The only option left was changing the shutter speed accordingly. Apart from the blue hue, see what effect this has on exposure:

1/250th

This version looks a little bit too bright, it's overexposed.

[1/250th @ f/5.6 with ISO200 - overexposed. Loss of detail in the highlight areas, bottom right]

1/400th

This version looks about right, it's correctly exposed.

[1/400th @ f/5.6 with ISO200 - nicely exposed. Enough detail in the highlights and shadows]

1/640th

This version looks a little bit too dark, it's underexposed.

[1/640th @ f/5.6 with ISO200 - underexposed. Loss of detail in the shadow areas, centre]

As good practice, why not take a few pictures of the same subject, but using a combination of different shutter speeds, apertures and ISO settings. Change one at a time and take a series of shots, then see what effect this has on your subject, and the way the camera records it.

All About ISO

Background
In the early days of film photography, the International Organization for Standardization (ISO) defined a standard to determine how sensitive the film was to light. This was known as the ISO speed. It is still relevent in digital photography today - the ISO equivalent speed is still a measure of how sensitive the CCD inside the camera is - and thus how quickly it will capture the image it "sees" through the lens.

Theory
ISO speeds normally follow the pattern: 50, 100, 200, 400, 800, 1600. A "slow" ISO speed is at the lower end, ISO 25, 50 etc. A "fast" ISO speed would be 800 or 1600. Most digital compact cameras work in the 100-400 range, although some go higher. Most digital SLRs will work in 100-1600, and some can even cope with 50-3200.

Examples
What does this mean for your pictures? Here are some advantages and disadvantages of two extremes of the ISO range:

ISO 100

• Best in sunny conditions outdoors
• Gives good colour saturation
• Best at recording high-contast scenes
• Images have good definition (sharpness)
• Shadows and highlights reproduced in good quality
• File size (for JPGs) will be lower - more images on a memory card
• Leads to slower shutter speeds - can cause camera shake (blur)

[ISO100 - there is good colour saturation and sharpness in the picture]

ISO 1600

• Best in dim conditions - overcast days or indoors without flash
• Gives reduced colour saturation
• Best at recording low-contrast scenes
• Images have reduced definition (sharpness)
• Shadow areas likely to suffer from ISO "noise"
• File size (for JPGs) will be higher - fewer images on a memory card
• Leads to higher shutter speeds - often avoiding blurry pictures

[ISO1600 - there is less colour saturation and sharpness in the picture]

In the above images, I have not done anything to alter the quality apart from cropping and resizing for the web. But this doesn't show the full story - here's a full-size comparision between the photos - showing the centre portion round the doorway:

[Left, ISO100 - good quality, colours and sharpness. Right, ISO1600 showing poor shadow detail and lots of "ISO noise"]

Of course, these effects go gradually from one end to the other as you go through 200, 400 and 800. It's always a trade-off between being able to take (any) picture (in dim conditions) and the technical quality that will result from using a high ISO speed. And the beauty of digital is that you can change the setting from one shot to the next if you need to - in the days of film, you were stuck with it for the whole roll!

So, if your camera will let you set the ISO speed manually, why not have a go at experimenting with different speeds next time you are out shooting? You will then learn what gives you the best results in various lighting conditions.