A sharp image – really really sharp – seems to be a constant cause for concern amongst serious photographers. And with good reason: judges frequently decline images that are ‘too soft’ or not ‘critically sharp’. Nothing beats a natural history image that is pin sharp in all the right places.
Of course, not all images have to be sharp. A romantic portrait can be soft, especially if blemishes are to be hidden. But assuming you want to get a sharp image, and you’re not getting them sharp enough yet, what can you do?
Sharpness is 80% about equipment, 80% camera technique, 80% image processing, 80% lighting and 80% things about the subject.
That isn’t bad maths!Get any of these things wrong, and you probably have an image that is not sharp enough. With luck alone, the chances of getting it right is 20% x 20% x 20% x 20% x 20% = .03% which is about one in ten thousand shots. So maybe the statistics are a bit questionable, but the point is that you have to get everything right to make the shot sharp. So let’s look at each of these areas.
Just before we do, there is one thing you already know without perhaps realizing: sharpness is mostly a perception. We can trick the viewer into thinking the image is sharp without having it pin sharp. Or we can make a sharp image appear soft.
It can be incredibly frustrating to see a photo taken with a compact camera that is sharper than the one you took with your expensive DSLR. This happens for several reasons, but the key one is that a compact camera is designed to be very forgiving, with its small sensor and wide angle lens providing a huge depth of field. However your DSLR will give a better result when it is used properly, and significantly better results in difficult conditions.
The camera itself doesn’t contribute much to sharpness.Resolution has some impact on sharpness, but not much, unless you are cropping heavily or producing huge prints. Some cameras have better low light sensitivity and produce less noise at higher ISO ratings.
Tip 1: An interesting recent theory is that ISO settings that are multiples of 16, such as 160, give clearer images than say 100.
The lens has a huge impact on sharpness. ‘Good glass’ will give you noticeably sharper images, particularly in tricky light, and nicer blurring of the out-of-focus areas. Prime lenses typically give superior results, and the bigger range zooms (eg 18-270mm) give poorer results. But any reasonable lens should be able to give you sharp images, as long as you keep away from the extreme settings for focal length and aperture.
Tip 2: Filters can reduce sharpness, but I think that usually the impact is minimal. Some photographers never use a UV filter, but I prefer to protect my lens glass most of the time.
Tip 3: A polarizing filter eliminates spots of extreme brightness (‘specular highlights’) so that filter can improve sharpness.
Tip 4: Of course, the lens and filters have to be clean! In some environments condensation can be a problem.
Tip 5: A lens hood will prevent stray light hitting the lens. I almost always use a lens hood.
Tip 6: A really good tripod and a remote control are excellent investments.
An image becomes blurry when the camera moves too much, the subject moves too much, the focus is out, or the sensor can’t pick up the light rays accurately.
Reducing camera movement starts with holding the camera steady, which ideally means a heavy, stable tripod.
Tip 7: If you don’t have a tripod, you can brace yourself against a wall, or set the camera on a table, a chair or on the floor. You can improvise a tripod with a cushion, bean bag or books.
Tip 8: Pressing the shutter often creates camera movement. Use a remote shutter release, or use timer delay.
Tip 9: For slow shutter speeds and long exposures, watch out for vibration or movement of your platform – don’t move around yourself while the shutter is open, or take a shot while people are walking past. Protect your camera and tripod from the wind.
Tip 10: For perfect results, enable mirror lockup, particularly for shutter speeds of more than 1/20th of a second and less than 2 seconds. A half-press of the shutter will flick the mirror up, so you can no longer see through the viewfinder. Wait a couple of seconds for any vibration to stop, then take the shot.
Tip 11: Select an appropriate shutter speed. For handheld images, a rule of thumb is to use a shutter speed no less than your focal length. For example, if I shoot at 200mm, I would aim for a shutter speed of 1/250th or faster.
Tip 12: You can get away with slower shutter speeds if your camera or lens supports Image Stabilisation (Canon), Vibration Reduction (Nikon) or similar.
Tip 13: When using a tripod or a stable platform, turn Image Stabilisation/Vibration Reduction off. Otherwise the stabilization mechanism can actually induce vibration.
Subject movement is less of a concern than camera movement. A tiny movement in the camera position translates to a big movement in the subject. You can shoot at very slow speeds if your subject is prepared to stay still.
Tip 14: How you reduce subject movement will be specific to the situation. You can ask a human subject to ‘hold still’ or wait for a moment when they stop moving. You could wait for the wind to ease, or move to a sheltered location. You could physically hold or tie up a subject such as a flower. If your subject is moving, you can pan the camera.
Tip 15: Subject and camera movement will be more obvious with a longer focal length, so if you can’t get a steady shot you might be better to compose a wide-angle shot instead.
Tip 16: You can freeze the subject using a flash unit. The speed of a flash is something like 1/8000th of a second, so a flash will stop a speeding bullet, regardless of shutter speed.
This one is obvious. If you haven’t focused accurately, your shot won’t be sharp. But how can you improve the accuracy of your focus?
The first answer is practice, getting to know your camera and lens, how the auto-focus settings work, and when the camera will struggle to get accurate focus. Testing has established that auto-focus is more precise than manual focus in most situations.
Tip 17: I have set my camera up for back-button focusing, which lets me auto-focus by pressing a button rather than half-pressing the shutter. This has helped my focusing considerably (unless I forget to press the button!)
Tip 18: You might find that your lens needs to be calibrated by the manufacturer. Some cameras support Micro-Focus Adjustment, which lets you adjust the point of focus forward or back by millimeters.
Tip 19: Adjust the diopter on your viewfinder. This adjusts the focus of the viewfinder – and only the viewfinder – to suit your eyesight, so that when the image is in focus it looks in focus to you.
Tip 20: For manual focusing, use LiveViewand zoom in on your subject, to get really precise focus.
Tip 21: For macro shots, rather than change the focus of the camera, lock the focus and move the camera slightly.
Tip 22: For objects at infinity, adjust focus manually using LiveView zoom. The infinity focus point depends on temperature and atmospherics.
Tip 23: For city lights at night, focus manually. The camera will have a hard time working out a clean focus point.
Tip 24: Enable the camera to beep when it has got focus. That will give you a feel for how long it takes. You might want to turn off that beep as it gets annoying. You will not get this beep if you are in Servo mode, as the focus point changes continuously.
Tip 25: Use AF Beam Assist from your flash. This function emits a light or an infrared beam from your flash to help the lens to focus. You need to be in Single Shot mode for this to work.
Tip 26: Choose the right point of focus. For portraits and wildlife, the norm is for the eyes to be the sharpest point. Often you will need to figure out what your subject actually is before you can determine where to focus. For example, in a landscape scene, is your subject the trees on the river or the mountains in the distance?
That leads on to Depth of Field, but that is a topic in itself. Suffice to say that you will need to get an appropriate point of focus and gradation of focus blur to achieve your objectives. The right Depth of Field will make your image appear much sharper than it actually is.
If you are still having problems with focus, some possible answers from forums are:
Tip 27: Check that you are using the right focus mode, and which points are selected in each image. Some software (eg DPP) lets you see where the focus point was, although that depends on the camera manufacturer. The focus distance or subject distance is available in EXIF data (but not visible in all software).
Tip 28: As the resolution on your old camera is lower, ironically sharpness issues are more obvious on your new camera.
Tip 29: If the problem is specific to a lens, you can get it calibrated.
Tip 30: Sometimes the lens and the camera just don’t like each other, especially if the lens is old or non-manufacturers. Some manufacturers lenses don’t work well with specific camera models.
Tip 31: A ‘hard reset’ of the camera can fix some focusing issues, or an ungrade of the firmware.
Tip 32: Sometimes the auto-focus points are misaligned – this needs to be fixed by the manufacturer.
Tip 33: Temperature can change the focal qualities of a lens.
The final area of difficulty is getting the light rays from your scene captured precisely by the tiny elements on your sensor. If a light ray strays from its perfect path, it will trigger the wrong element and that will show up as a loss of sharpness.
The problems happen within the lens and with the direction of the light from the lens to the right pixels on the sensor. Some are natural and cannot be avoided (defraction). Others are due to limitations of the lens, which can only be avoided by better quality and more cost (aberrations and distortions).
If you use aperture settings or focal lengths at the extremes of your lenses capabilities, you often get problems, particularly around the edges of the image. That is simply because the engineers have pushed to the limits of acceptable performance. Optimal performance will be at moderate settings, perhaps f5.6-f11 for aperture.
With the aperture wide open, or then aperture closed tight, the image can be blurred due to lens design issues. You would work about two stops away from the minimum and maximum aperture (f4àf8and f32àf16)
Bright spots of light are hard for the camera to deal with. Often the light will be diffracted by the lens and end up on the wrong element, causing a blur, flares or star effects.
The key to getting this right is to get the right exposure, and to avoid situations where the camera will struggle.
Tip 34: Recompose so that the background does not include bright highlights, wait for the light to improve, or use a diffuser.
Tip 35: Change your shutter speed and ISO to get a moderate aperture setting.
Tip 36: Sometimes under-exposing by half or one stop can avoid the worst effects of harsh lighting. But it is much better to get the right light and expose correctly.
Tip 37: Remember that with digital we have an opportunity: we can hedge our bets by taking several frames, knowing that the chances are that one will have all the stars aligned. And we can use Auto Exposure Bracketing (AEB) to take several shots at different exposure levels. Try taking the same shot from different positions and with different settings. This lets us push the boundaries and still have a reasonable likelihood of a successful capture.
Tip 38: Keep the parts of the image you want really sharp towards the centre of the image, not on the edge. You can crop later to get it on the edge if that’s where it should be.
So now we have a reasonable capture, and it’s time to move onto the computer. On first sighting you might be slightly disappointed, but keep the faith.
I am assuming that you have a RAW file to work on, not a JPEG. If you have a JPEG, the camera will have already done a lot of processing, so it will look ‘better’ than the raw file, but you can’t do much with it. The raw file will appear flat and soft. It appears soft because there is way more image data available than the computer display can handle. Zoom to 100% view and the sharpness will be more obvious.
Tip 39: Note that the display on your camera is effectively a processed JPEG, even if you shoot raw. You can change the contrast and sharpness settings on your camera, but that won’t change the actual data recorded in the raw file, only what shows on your camera’s display.
Some image processing ‘sliders’ have a direct impact on the sharpness of an image, others have an indirect impact that can be positive or detrimental.
The most obvious is the sharpness slider and the related options (such as radius and threshold). I won’t dwell on these here, as they are clearly described in software manuals and handbooks. Do note that there are two places to sharpen an image: input sharpening, and output sharpening. As a general rule, raw files will need some input sharpening but don’t overdo it.
Output sharpening is done as a final step and should be specific to the intended output device and resolution – a 1024×768 projected image, or a 10×8 inch inkjet print.
When you resize an image for output, you usually have the chance to set the level and method of sharpening. For example the resize function in Photoshop lets you choose ****. In Lightroom, you can choose the output resolution and sharpening amount.
Tip 40: A print typically doesn’t need as much sharpening, but printers vary in the amount of sharpening they apply. Paper type also has an impact. A cotton rag fine art paper is going to look softer than a gloss print.
Tip 41: The following sliders have a significant and fairly direct impact on perceived image sharpness:
Tip 42: The following sliders can have a significant impact on perceived image sharpness:
- Recovery (darken highlights)
- White Balance
Tip 43: The following sliders usually have a detrimental impact on perceived image sharpness:
- Chroma noise reduction (partly offset by detail slider)
- Luminance noise reduction (partly offset by detail and masking sliders)
- (lighten shadows)
Tip 44: Sliders such as Recovery will initially improve sharpness, but then often soften it badly.
Over-applying any of these adjustments will make the image appear over-sharp and create artefacts, particularly if the original image is not sharp.
These adjustments are all global, affecting the whole image. Most of them can be applied selectively, to parts of the image. Remembering that sharpness is perception, one way to make the image appear sharp is to make the subject relatively sharp. You can do that by sharpening or highlighting the parts of the image you want to look sharp, or by blurring or darkening other parts of the image. For example you can:
Tip 45: Crop, clone out or blur parts of the image that are sharper than the point of critical sharpness. For example if a photo of a bird in a tree locked focus on a leaf in front of the bird, deal to it.
Tip 46: Selectively sharpen the eyes and other critical areas on a portrait or wildlife shot using the Clarity and Sharpen sliders
Tip 47: Selectively blur background elements using the Blur tools or negative settings on the Clarity/Sharpen sliders
Tip 48: Dodge (lighten) or increase contrast on specific areas you want to de-emphasise or highlight
Tip 49: Burn (darken), partly desaturate or reduce contrast on specific areas you want to have reduced emphasis
Tip 50: Apply a vignette to the whole image, which will make the subject stand out more
There are some tricks that could get you a sharper image:
Tip 51: Crop the image. You will appear to have more depth of field on the section that is left than you would have if you had moved or zoomed in that close.
Tip 52: Processing an image in black and white can make it appear sharper. However, that is not a good reason to use black and white.
Tip 53: HDR software can improve ‘micro-contrast’ to make an image appear much sharper.
Tip 54: If you take several frames at different focus points (perhaps by moving slightly forward and back after locking focus), you can layer and mask these together in Photoshop to create a Focus Blend image.
Good light is everything. Good light is strong enough to bring out the colours and contrasts in the scene, and directional enough to create shadows that emphasise structure, and therefore imply sharpness.
Too much light pushes the capabilities of the sensor and lens. If you emerge from a dark room into bright sunshine, it is pretty hard to make out detail. The camera has the same problem, and the bright areas in your image will look hazy. You can rescue some sharpness in post, using the Recovery slider, but the damage has mostly been done.
Insufficient light can lead to blur due to camera or subject movement, or noise due to high ISO settings or long exposures. ‘Flat’ light does not provide enough contrast or saturation to separate the elements in your image.
Your exposure needs to be right for the light as well. There are various theories about exposing to the left or right, but I usually expose ‘correctly’ provided there are no relevant highlight alerts, and bracket if unsure.
Tip 55: Bright sunshine in the middle of the day is the worst time to get a photograph. Early morning and evening light is usually best, or diffuse light under shade or cloud.
Tip 56: Also watch for atmospheric conditions. Obviously a mist or dusty air will not help with a sharp image. The atmosphere is often clear after rain or early in the morning. ‘Red skies’ indicate wind-borne dust (evenings) or high humidity (mornings) so neither is a photographer’s delight!
Tip 57: Another option is to make your own light, using studio or camera flash, or some other lighting source.
Tip 58: You can mix ambient light and flash light by using a longer exposure for more ambient light, and a smaller aperture for less flash light, and vice versa. You can adjust the flash power, position, direction and zoom and soften it with a softboxor bounce-flash.
Tip 59: Use a Polarising Filter to avoid specular highlights and increase saturation.
Some subjects will look sharper than others, and you might not have full control over that. But you can control how you frame the subject, in relation to light direction and the background.
The background should usually be darker than the subject and free from distractions and highlights. You might also want a blurred background, so your subject appears relatively sharp.
Tip 60: If you want your background more blurry, you need to use a longer focal length on your lens, and a wide open aperture.
Tip 61: Some colour combinations appear sharper to our eyes than others.
|black on yellow|
appears sharper than
|red on blue|
even where they are both focused the same.
|Green on blue|