Sharpness is overrated. Sure it is. But you wouldn’t think so if you spoke to most serious photographers. I mean, you’ve bought all that expensive kit, why would you produce a blurred photo with it? Well, there might be reasons, but for a while just humour me. Let’s see how we would go about taking the sharpest picture we possibly can.
Components of a sharp photograph
For a photograph to appear sharp to the viewer you have to take care of a number of different and sometime conflicting aspects.
- Sharpness (acutance) and resolution in camera
- Movement blur (or absence)
- Sharpness (acutance) in processing
Sharpness and resolution
Resolution: the ability of the camera system (not just the sensor) to record increasingly fine detail. Measured in lines per millimetre. In landscape pictures, you’ll pick out every detail on every blade of grass.
Sharpness (ok, technically Acutance): the ability of the camera to record local contrast providing a readily identifiable change from one tone to the next. In your landscape, you’ll be able to separate every blade of grass from its neighbour.
A camera with a high pixel count has more potential for recording sharp pictures (pixel resolution), but the final resolution of an image coming out of the camera (spatial resolution) depends also on the capabilities of the lens and the processor in the camera as well.
OK, so what do I do?
So, before we get to focussing, holding the camera still and other compromises, try these to get the sharpest result out of the camera:
- Use a high-quality lens. Most lenses these days produce far more resolution than is strictly needed, but we’re aiming for as sharp as we can get. Prime lenses are typically sharper than zooms. Good sources of information about the relative performance of lenses include Fred Miranda, DXOmark and DP Review
- Avoid “soft-focus” lenses. Some manufacturers make lenses which reduce contrast on purpose for aesthetic effect. Older lenses without the special coatings used these days do the same thing. They have plenty of resolution but the extra light bouncing around inside the lens softens the image by reducing the contrast.
- Use a smaller aperture – f8 or higher. This concentrates the light more through the centre of the lens where its performance tends to be best. Less of a concern on most modern lenses though some wide-angle zooms can be shocking at large apertures.
- Don’t use a really tiny aperture. After a certain point, typically f13 and higher, light waves start interfering with the edges of the aperture and start softening the image. If you’re after maximum sharpness, don’t go smaller than f11 generally.
- Use your camera’s base ISO setting. Even with today’s ISO-invariant cameras, you can still see a difference, however minute, between images taken at 100 ISO and 200 ISO. Most of the time this doesn’t matter, but if you are seeking the absolute best performance, switch to your camera’s base setting (which may not be the lowest setting available). For Canon DSLRs, this is 100 ISO.
- Use a camera with a high-resolution sensor ie more pixels. An APS-C sensor or larger will do perfectly well, but the bigger the better. For the very best image, one of the new medium format cameras would be the thing. Cost, sadly, is a controlling factor here. After a certain point though, for a given sensor format, pixel density will start to impact sharpness, so move onto:
- Use a more modern camera. Current models typically perform better than earlier ones, especially in the digital world. My 12-year-old Canon 5D Mark 2, while still an accomplished camera,easily outperformed by the more recent 5D Mark 4, and not just because the newer camera has 9 more megapixels on the sensor.
- Fill the frame and use the entire file. The larger your subject appears in the photograph, the more pixels you will have available to you to sharpen on your computer. Avoid cropping whether in the camera (by reducing its pixel resolution) or on your computer.
Focussing discussions get very technical very quickly. The aptly termed “Circle of Confusion” rears its head and everyone gulps, remembering how they struggled with equations at school.
The classic advice was always: “f8 and focus one third of the way to the horizon” and as a rule of thumb that’s still pretty good.
Happily you just have to remember one thing about focussing – it all depends! So, given this article is designed to be a practical guide to producing the sharpest possible image, what do we need to take notice of?
You only need “acceptably sharp”
First of all, from an optical point of view, even the best focussed picture is at perfect focus at one distance only from the camera. The rest of the picture is simply acceptably sharp. If you think that “acceptably” sounds like a fudge factor, you’re right. Focussing is always an activity with compromises, which include:
- Distance of viewer from the final picture
- Size of the final picture
- Size of the camera sensor
- How the picture is displayed – print or screen
- Focal length of the lens and the aperture used
From these variables, we can calculate how we need to set our cameras to achieve maximum apparent sharpness of focus (depth of field) through our picture. The calculation helps us determine how much of our picture will be “in focus” if we set the camera to focus at infinity.
Just tell me the answer already!
After all this it turns out that if I set my Canon 5D Mark 2 full frame camera at f8, and focus on infinity (or some distance 1000 metres away or more) the closest that things will be sharp are:
|Focal length||Closest focus distance|
In real life when I photographing landscapes, I just set my camera to f8, focus halfway to the horizon and try not to include anything much closer than 3 metres away. Look again at the picture of Mertoun Beat above, especially at the bottom centre. The leaves at bottom left are still soft but they were just under my feet.
To make sure everything is in focus I usually use Live View and zoom in on near items to check they are sharp.
Different camera? Different lenses? There’s an app for that. Actually, there are many apps for depth of field and hyperfocal distance calculations. Hyperfocal Pro for Android phones gets good reviews.
OK, but what about close-ups?
OK, focus stacking is what you want. But that’s way too specialist for this article, and involves taking lots of pictures of your one subject. Each picture focusses on a different point, then you merge them all together in Photoshop or the like.
Blurring, intentional or otherwise
So you’ve sorted out your best camera and lens. You’ve got yourself in the right place with the right focus. But your pictures are still soft. Next thing to eliminate is unwanted movement blur. If you are handholding your camera this will be a great place to look for improvements.
Keep your camera still
You will not get really sharp pictures with a handheld camera. They’ll come pretty close though. Things to do to make sure you improve your chances of a sharp picture are:
- Hold your camera securely. Use two hands, one under the lens, the other on the grip at the right with finger poised to press the shutter button.
- Use the viewfinder. Don’t take your photograph holding the camera like a mobile phone with your arms outstretched. Just pressing your eye to the viewfinder provides another point of stability between you and your camera.
- Tuck your elbows into your sides, and stand with your feet slightly apart, one ahead of the other to maximise your stability.
- Stay relaxed, don’t overgrip the camera. Breathe out as you press the shutter button.
- Choose a suitably fast shutter speed. The classic advice for a full frame camera is to turn the focal length of the lens into a fraction; that’s your shutter speed. For a 100mm lens, your shutter speed should be at least 1/100th of a second. (With a smaller sensor like an APS-C, you should choose the next fastest shutter speed for this equation to work reliably, in this example 1/250th.)
- Switch on image stabilisation on your camera or lens. It IS switched on, you say? Have you checked? There you go.
So here’s the compromise
Better still use a tripod or some other camera support. This will certainly help make your pictures sharper.
- Make sure you have tightened everything up: the plate under the camera, the leg clamps, the various adjusters round the tripod head, and where the head attaches to the tripod. Looseness in any of these can impact on your ambitions for sharpness.
- Don’t touch the camera with your fingers to take the photograph. Either use the self timer set to 2 seconds or more or, preferably, use a remote release. You can get one with a built-in timer, useful if you have a camera as old as mine.
- Switch off image stabilisation. Generally considered a good thing for sharpness. Some makers of lenses reckon they have built in facilities to identify when the lens is on a tripod to avoid having to switch it off. There are mixed reviews for this so you need to make your own mind up by testing it. You can find special instructions for Canon users here.
- Lock your mirror up. This applies to SLRs, not mirrorless cameras, obviously! The theory is that the shock of the moving mirror coming shuddering to a halt can generate minute movement blur and soft images. If you’ve done everything else, or you’re using an ancient medium format camera with a mirror the size of a small county, this is worth trying.
Keep your subject still
It might not be you that’s moving. It might be your subject, especially if they are squirming children. How do you keep them still short of fastening them down?
- Use a high shutter speed. If they are running around you may need to go as high as 1/250th or 1/500th. You may then need more light, and this is where the compromises I mentioned earlier start to bite. A bigger aperture, of a higher ISO are your options, but each has downsides when it comes to sharpness.
- Hold your subject still. This is more for vegetation, not so much the wriggling infants. Taking photographs of flowers in a breeze is a thankless task so come prepared with clips, string, supports and something to act as a wind shelter. Or wait for a still day. A very still day.
- Improve your panning techniques. Although not really in the scope of this article, getting your panning right when photographing passing vehicles or runners will pay off with sharpness where you want it and a nice blurred background.
If you take pictures as raw files, you’ll find the camera does very little work on contrast to them. As a result they appear at first to be somewhat undersaturated and soft. The clue’s in the name: camera manufacturers assume you know what you’re doing when it comes to raw files, and sharpening is one of the things you’ll be doing to your files.
Sharpening in software relies on increasing the apparent contrast along any edges in your image. Look again at the reeds in the last picture. The reason they look so defined is because sharpening has increased the contrast along the length of the stems. Images with clearly defined edges to start with have an advantage over those with less definition when it comes to making them appear sharper.
Again there’s probably a full article (or two) to write about software sharpening, but here are some guidelines for Lightroom’s Sharpening dialog which will work in many cases:
- Amount to 75
- Radius to 1
- Detail to 75
- Masking to 50
These are only guidelines to start from and you’ll soon develop your own techniques. Remember to check the results at 100%.
Finally consider where the final image is to be viewed. The various calculations in this article assume the final image will be a 10×8 inch print, held 25cm away from your eyes. If you look closer you may see imperfections. If you print it bigger and hold it the same distance away there may be imperfections.
At worst if you print it for a bill board and look at it up-close, you’ll defintely see the grain!
Having said this, these are probably edge cases. For a given size of image there’s a suitable viewing distance, and that’s been taken account of in the depth of field table calculations we looked at earlier.
If your image is for viewing on screen, the far lower resolution available to screens compared with printers means it’s fairly easy to be satisfied with a picture when you view it in Photoshop but less happy about the print.
Viewing it at 100% to check sharpness and noise is recommended for best results.
But do you actually want sharp pictures?
Applying sharpness to an image is an aesthetic choice. It is not necessary to identify each wave or wisp of cloud in every picture you take. Sometimes a software approach will suit the subject matter better.
As an antidote to the landscape photographer’s demand for every blade of grass to stand out in sharp relief, check out this book:
When you do it on purpose, out of focus effects can be intriguing, and probably worth an article of their own.