Metering Modes

If you’re new to photography, the graphic below helps to explain your camera’s metering modes.

Segment (or Evaluative): the meter calculates exposure based on readings from different areas. The current exposure information is compared with evaluative metering data stored in the camera. The most appropriate exposure is calculated in an instant.

Partial: the meter takes a reading from about 10% of the overall image. This can be very helpful when the subject is mostly light or dark.

Spot: similar to partial, but reading taken from only a central 2 or 3% of the image area. Accurate if used properly.

Centre-weighted average: the meter takes a reading from the whole scene, but gives much more importance to the central area.


Photos from Phones

I’d driven some distance from my home to my favourite secluded spot along the coast, and was walking a deserted county road when I came on this view. It was bitterly cold but totally calm. The feeble, late winter sun was just about to dip behind the Irish drumlins.

All I had with me was my mobile phone. So I stopped and took just one shot.

If you’ve good experience editing digital images you’ll possibly recognise how fragile this auto-everything JPEG is. The original’s weak tones and excessive compression were lovingly edited.

My plan is to have a modest quality print made directly from the phone’s full megapixel image (above) and then make a detailed flatbed scan of it for a careful TIFF edit. This should get me a much larger print I can have framed-up for the wall.

On another occasion I’d gone for a walk cameraless once again – you’d think after 30 years I would learn. The special warm light of an early Summer dawn was irresistible. Fortunately I had the same phone in my pocket so I snapped the scene as best I could.  I can now use the same print-to-scan-to-TIFF process to get the best possible results.

These won’t win me any prizes but among friends and family they are two of my most popular images. So much for expensive gear! If photography seems to be in your DNA you’ll not want to miss an opportunity when it arises. We use what we can to get the image back home. Then we can try to make something of it.


RAW and JPEG: What’s Your Preference?


Every now and then someone on a photography forum will ask, “What’s the real difference between RAW and JPEG?” What will we actually see in our images and prints? Is there always a clear visual advantage to shooting RAW all the time? Answering these questions isn’t that easy, unless you own a company that sells RAW conversion software.

Forums are a consistent source of misinformation and unhelpful personal bias. Here’s a particularly good RAW-related example from a few years back: “Who needs JPG except websites? The only format is RAW…”

Discussing RAW and JPEG shouldn’t become an inconclusive debate about what’s best. It should be about an informed choice — but you wouldn’t think so when you listen to some photographers. The above comment was a response to one of my forum posts. I’ve come across many comments like this. I wish I’d kept them all. They typify the wonky mindset of those who religiously shoot and process RAW for “serious” work and can’t understand why everybody else doesn’t do the same. Do they really know their subject? I have to wonder.

Here’s another example of forum sermonising: “If you only view on a PC screen JPEGs are fine — don’t fret over it, those who DO understand the difference will continue to shoot RAW.” And finally, from a couple of days ago: “Shooting in JPEG when there is no specific need to is just sloppy photography… There is positively no debate here.” In response I pointed out that there are plenty of amateurs and professionals who don’t use RAW unless there is a specific reason to do so.

These intransigent opinions smack of elitism and hardly bring balance to the discussion. In fact, it’s all a bit misleading, particularly for conscientious amateurs who are trying to make key decisions about digital photography based on their own preferences, resources and circumstances.

We all have our own way of working. As an enthusiastic amateur, (that context can be important), I typically prefer to work with JPEGs. Before editing I usually convert them to a layered format, or TIFFs. This avoids visual damage caused by working on the original JPEG and repeatedly saving it. I then apply the non-destructive enhancements that are needed.

My cameras are usually set to record RAW and JPEG. For the last 12 years my tweaked JPEGs have been more than good enough for quality prints, and I’m not easily pleased. But having RAW versions available means I can make use of the extra data on those occasions when I actually need it. (Sometimes I experiment with in-camera RAW conversions.) A lot depends on the image itself, exposure choices, shooting conditions and what manipulation is envisioned. It helps me a lot to be very familiar with powerful image-editing software, in particular its fundamental set of tools.

JPGs have useful potential. Here the shadow detail was selectively edited to improve the dynamic range of the print.

There is a tangled mass of nonessential technical information related to this subject. A little of it is even interesting — but only a little. Essentially, one of the amateur’s biggest challenges is learning how to creatively use image-editing tools. If we shoot RAW we’ll start off by editing in conversion software. If we shoot JPEG, for more typical editing we can load our shots into conventonal software that supports layers. Then we can save them as an appropriate format and see what needs to be done to selectively make the best use of the image’s content, tones and colour. With a little foresight we can shoot according to our editorial preferences.

Should we shoot RAW only and edit the image in conversion software that may encourage us to apply tonal edits to every pixel? It’s likely that many converted images will benefit from additional selective work in conventional image-editing software. More powerful RAW converters don’t have layers but do have tools that can make very useful targeted adjustments.

Whatever the case, every effort should be made to expose the image intelligently in the first place. Whether we’re working on RAW files or JPEGs, major tonal adjustments are best avoided. The key elements of the scene should hold reasonable shadow detail and show no signs of damage to the highlights where it really matters most. Sometimes it’s best to sacrifice deeper shadow detail to make the best use of lighter tones.

Prudent digital exposure may produce images that won’t look quite right until they are edited in software. An image’s more significant highlights are usually key. If they’re blown the image will usually suffer. Cameras can be set up to produce saturated, sharp JPEGs with good contrast that will need little or no work in software. But this can set unrealistic limits on the benefits of image-editing. It’s a fact that there are amateurs and successful pros who are happy to shoot JPEGs most of the time for their best work. Their images are impressive and editing is probably minimal.

Assuming a digital image is sensibly exposed, what’s the actual difference between RAW and JPEG? A lot depends on how much manipulation is needed, and where it’s applied. High quality JPEGs are a visual compromise. Data is stripped away because generally our eyes don’t need it. High resolution well-exposed JPEGs can be tonally impressive. But the problems can arise during prolonged and targeted editing when the compressed data will start to show the strain. For example, creating B&W images from channel-separated JPEGs reveals data limitations. Individual colour channels may show random blotches associated with in-camera colour interpolation and JPEG compression.

Generally, for top results from JPEGs it’s best to not get carried away with in-camera sharpening and contrast settings. Some prefer vivid colour but it can lead to unrealistic skin tones and be problematic when the image has colour casts, for example. It’s good practice to shoot at the lowest ISO setting possible.

With good prints in mind, JPEGs are more resilient than many RAW-only amateur photographers realise. It is in fact possible to use software’s sharpening tools to subtly enhance selected areas of a camera’s JPEG image. This is especially true if we have been cautious with the sharpening setting before we shoot.

Our cameras apply sharpening to JPEGs before they are compressed. So sharpening the JPEG again in software may draw attention to the compromises of compression. This may show up in a larger print. We especially need to look out for obvious halos. It pays to remember, too, that some areas of an image will probably benefit more from sharpening than others. We will learn a lot through trial and error as we selectively sharpen sections of a JPEG image, if needed.

Prolonged editing (within reason) shouldn’t be a problem with most RAW files because, unlike a JPEG, the data has not been processed and compressed (effectively reduced) in-camera. RAW files are more robust in editing because there’s more information to work with. That’s why exposure is generally more important when shooting JPEGs. The more off the mark tonal capture is the more work will probably be needed in software. So it’s possible the JPEG image will start to visually break down.

A camera’s JPEGs edited in a layered format (preferable) or as a TIFF are flexible in the shadow areas, especially images captured by full-frame SLRs. However, smooth areas of blending tones will show signs of damage when processed too much — and it might not take a lot of manipulation before it happens. (It should be noted that not everything will be noticed at typical viewing distances. We shouldn’t get hung up on 100% on-screen detail.)

In the images below extreme editing has magnified the limitations of JPEG files. The RAW file has clearly suffered less damage where the tone is smooth.

It’s these more sensitive areas lacking in detail that can easily show the inherent weaknesses of JPEG compression. If JPEGs are well-exposed we probably won’t need to significantly adjust their tonal values with Curves or Levels. Slight damage can sometimes be subtly smoothed away, (depending on the context), but it’s best if a JPEG’s smoother tones are left well alone.

RAW is useful for getting extra detail from the highlights. But the comparision below, processed in Canon’s RAW-editing software, suggests how little benefit there can be. In some contexts it’s useful, but sometimes it’s no big deal.

Having a very good grasp of well-equipped image-editing software means JPEG images can be usefully manipulated, particularly if they’re shot at lower ISO settings. As mentioned, converting from RAW may well involve extra steps in software processes, whereas a properly exposed JPEG can be brought directly into image-editing software and edited in another format for quality prints and viewing on various devices. And of course, even large megapixel hi-res JPEGs take up a lot less space everywhere, although for most this isn’t the problem it once was.

However, in actual practice it’s a good idea to intelligently make the best of both file types. Some situations clearly cry out for RAW because RAW files will withstand the more intense editing that’s required. For example, an image with a really heavy colour cast can be balanced fairly well if shot in RAW but will probably have to be binned if it’s a JPEG. Contrary to what you may read on forums, more typical colour correction, global and localised, is sometimes possible when working on a JPEG.

Long exposures may produce the best results when shot in RAW. Depending on our goals, RAW will give us more options when processing from colour to B&W. Very misty landscape shots packed with subtle shades, graduated tones and indistinct details will benefit from RAW capture, especially if several editing processes are essential.

It also makes sense to include RAW when shooting indoors without flash, although the larger files take longer to save to the card and in some contexts this will be a drawback. Indoor flash shots in a confined space may be adversely affected by the colour of walls, ceilings, electric light and furnishings. This may need correction.

And of course, having all the data to work with can occasionally pull us out of a hole when we’ve made a mistake. Hopefully mistakes are rare!

In conclusion, many amateurs are shooting RAW because they’ve been led to believe it’s the one true path to quality, regardless of the context, subject or general shooting requirements. But this isn’t a balanced point of view. JPEGs produce excellent results when they are properly exposed for the subject, and appropriately edited and viewed.

On shooting JPEGs:

“Both formats are capable of the highest quality images… Unfortunately tech folks push Raw without consideration as to how photographers like to work…” (Rob Sheppard).

“In the end, it doesn’t really matter which format you choose to shoot in, as long as it is right for the kind of photography you do – you might find you switch from RAW to JPEG depending on the subject matter. The only way to satisfy yourself about the debate is to try both modes and see what works for you” (Steve Young, Outdoor Photography).

“Why should you consider shooting RAW instead of JPEG? The answer… is mainly one of flexibility, with a few quality issues thrown in as well… a JPEG is a compressed file whereas a RAW file… contains pure uncompressed data… Whether this loss of data causes the JPEG to be to be visually inferior to the RAW file is subject to debate and I have made a number of tests that demonstrate that, although on paper there should be a difference, in reality there is very little visible difference…. a RAW file has more dynamic range than a JPEG, which cannot be directly seen. But when you start to make colour corrections to your images, you will soon see that a RAW file has more tones to play with and therefore you can correct them with a higher degree of accuracy and control” (Andy Rouse, Understanding RAW Photography).