Image Clarity

I was contacted by “Dan” via the photography-on-the.net forum who had been looking through my site and had a question about my images….

I like the clarity, composition of your photo’s as viewed on your web site. How do you get such quality of your photo’s. Are they specifically sized for web ?

I thought responding to Dan’s query would make a useful blog post – so here it is! Hopefully I’ve written this in a way which is accessible by those who already know a thing or two about photography, but also those which may be relatively new to it.

First off, image clarity, as with most photography and art in general is subjective. What looks crisp and sharp to one person, may look overdone and distracting to another and as always the most important thing is composition and your subject – a blurred shot of a great subject will normally be more pleasing to look at than an ultra-crisp shot of something dull and uninteresting.

Bearing all of that in mind, the way I would explain obtaining clear, sharp images is in the following key areas (not necessarily in order of importance) – capture stability & exposure, equipment, post-processing, presentation.

  • Capture Stability & Exposure

It can be easy to come away with the impression that since the arrival of digital photography the most important part of producing a sharp image is what you do with it on a computer after you have taken it. However, the most critical part of taking a picture, in my view, is what happens the moment you press the shutter button. If you don’t capture a strong image no amount of post-processing will save you (although the likes of Photoshop can do some amazing things).

Stability is key. If you have horizontal or vertical movement captured whilst the shutter is open then this immediately limits the sharpness of the shot. There are things you can do to ensure this is limited as much as possible. First off, your own technique, how do you press the shutter button? There’s a similarity with rifleman technique – if you prod quickly at the button you will introduce undesired movement in the camera; squeeze it gently instead. Also, be comfortable, don’t hold the camera in unnatural way just because someone else holds it that way – hold it the way that works for you. When I first started taking shots with an SLR I used to push the eyecup into my face quite hard thinking it would help keep the camera steady, instead it just introduced movement in my forearms. Next, stabilise yourself. If you can lean against something, do it. If you can kneel or sit instead of standing then why not. Anything you can do to stop YOU wiggling and bouncing around will also stop the same movement creeping into your shots.

Exposure. The exposure is the combination of parameters which translate into how much light is captured by the film and/or image sensor. In simple terms, this is a balance between ISO, shutter speed and aperture size.

Choons

The high iso adds some grain to this shot but it adds to the picture. A large aperture was used giving a blurred background, but the contrast on the mesh draws the eye into the reflection and gives a sense of clarity

ISO in the days of film was effectively a measure of a film’s sensitivity to light, high ISO films would be highly sensitive and require relatively short exposures to light before producing an image. Low ISO being the opposite. With digital sensors ISO is still a parameter, albeit it is more to do with digital amplification, but it operates in a similar fashion – the higher the ISO, the shorter an exposure length or the less light needed to produce an image. The impact on clarity/sharpness here is that generally higher ISO levels produce more noise – the grain-like look you would often see with old film black & white shots. You will see a similar outcome with high ISOs on digital cameras but I find not only do you see more grain, but you also see a drop in detail. Try and keep the ISO low if you can.

Aperture. This is the size of the “hole” which opens in a lens to let light through. The bigger the hole the more light reaches the sensor within a given period of time (governed by the shutter). Generally, the bigger the aperture the softer the overall image. This will vary from lens to lens but most have a “sweet-spot” where they are at their sharpest. I find this tends to be a few “stops” smaller than its maximum. So for a lens that opens to F1.8, it is probably at its sharpest at around F4 and higher (but to a point). Large apertures also produce a shallow depth of field (think blurred backgrounds) which can be quite tricky to get right – if you don’t get the subject you want in sharp focus it will create an impression of lack of clarity. Its worth mentioning that accurate focus is obviously a huge factor when taking a shot. The autofocus on modern cameras is pretty amazing, but make sure you get the right part of the image in focus. This is especially true when taking images of people. If you don’t get the eyes in focus and perhaps had the tip of the nose in focus instead then the image will look blurred. Focus technique is a whole area itself to chat about at some point.

Shutter speed. Along with the aperture and ISO, the shutter speed governs the amount of light reaching the sensor. It is also very important to tailor it to what you are shooting. If you are taking shots of sports do you want to freeze the motion (fast shutter) or give a sense of movement (slow shutter). If you are taking a portrait you don’t really want the subject to look as though it is moving, otherwise this will look blurred. The shutter speed also needs to be considered based upon your focal length. (I’ll save discussions on sensor sizes and effective focal lengths for another time). The longer your focal length, i.e. the more zoom you use, the more your physical movements will be visible in the image – think of this like the difference between balancing a pencil upright on your hand and balancing a broom in the same way – move your hand a small amount and the pencil will move a small amount, move your hand a small amount and the end of the broom will probably wave around quite a lot. There is an old 35mm rule of thumb that you should never drop your shutter speed slower than your effective focal length to minimise shake. So roughly that means if you are shooting at 200mm, you should have a shutter speed no slower than 1/200 of  a sec. Sensor size is a factor here as that modifies effective focal length, but I won’t go into the depths of that now.

  • Equipment
Toronto HSA Crew

A bright day allowed for a small aperture and fast shutter speed. Bumping the contrast and adding sharpness and saturation makes for a very clear image

I’m not going to tell you that you have to spend thousands on cameras and lenses to get sharp/clear images. The best camera is the one you have with you when you see a great picture, a less than perfect picture is better than no picture. However, my experience is you get what you pay for. I use Canon DSLRs and lenses and as I have upgraded to better lenses, I have seen the clarity increase and my advice to someone just getting into SLR photography – invest in lenses. The clarity of my images is most influenced from an equipment point of view by the lens sharpness, contrast and saturation. However, I also have a Panasonic LX3 which is a “point-and-shoot” camera with a fixed lens and much smaller sensor than my Canons – does that produce images with high clarity? Yes it does. All of the same rules apply around exposure and stability when shooting with any camera. There are also equipment aids which will help you achieve a clear shot – tripods, monopods, Gorillapods etc. Anything which fixes the camera to something other than your shaky hand will help you shoot with lower shutter speeds. Many cameras and lenses now have image stabilisation – IS. This can act as a virtual tripod to a small extent but will not help you if you need to freeze action with a fast shutter (and in fact aren’t really neccessary at those speeds anyway) – many of the shots I have taken in low light have been helped by the IS in my Canon 17-55mm F2.8 IS.

Calibration is also important. By that I mean calibrating the screen (and printer if you print) using something like a Spyder 3 Pro. The long and the short of it is that making sure your screen is calibrated ensures that the hours you put into editing your images will translate to the final outcome. I’ve had first hand experience of editing on an uncalibrated screen and then receiving a print that seemed relatively dark and unsharp because what I saw on screen was not what the printing device would produce.

I could write a ton about the impact of different types of equipment, but good technique applies to using all gear. One key tip I do have though is make sure your front element is clean before you take shots. I’ve lost count of the amount of times a stray finger, perhaps covered in a smudge of chocolate or drop of Guinness has created a lovely film over the front of a lens – your pictures take on a wonderful foggy look – definitely not sharp or clear. I see this mostly on point and shoot cameras where the front element is easily touched when pulling the camera out of a pocket. – the iPhone is awful for this.

  • Post-Processing

You’ve taken a clear shot and uploaded it to your PC/Mac. Then using your favourite image manipulation program (The Gimp, Photoshop, Lightroom, iPhoto etc.) you want to improve the clarity/sharpness of the image. Again, post processing is an area I could write war and peace on (and I’ll probably write a separate post about it) – it’s not so much about playing with baths of chemicals in trays these days but more about careful use of various sliders, buttons and filters. When it specifically comes to sharpness/clarity I would say a few things –

Perfect Rain

The most prominent rain drops in this image were selectively sharpened with the rest of the image being left relatively soft

  1. Sharpen for your intended medium. If you aim to only show your images online/on-screen, then the level of sharpening required is normally less than that required for printing.
  2. Zoom to 100% when applying sharpening so you can see the full impact. Over-sharpening produces ugly halos and artifacts on your images you may miss when viewing at a fit-to-screen size.
  3. Bump up local contrast to give an impression of greater clarity – deep blacks and strong highlights give the impression of a bold, strong image. (Too much looks ugly though)
  4. Sharpen last – if you are editing many aspects of an image, sharpen at the very end of the process.
  5. If you are resizing (and chances are you will for the web), then apply some sharpening at the output size. Many programs will offer this as a specific option.
  6. When resizing you often have resizing techniques to choose from – bicubic will produce sharper images than bilinear
  7. Be careful with noise reduction. Many people get annoyed with noise/grain but often I find it can add to the feel of an image. However, if you do use noise removal make sure you don’t go overboard and reduce the detail in your image and thus produce a smoothed or smudged looking picture – I would also recommend removing noise as the first step of image editing. Noise first, everything else, sharpen last.

A small note on capture format. I make most of my images in RAW format instead of JPEG. Think of RAW like a film negative and JPEG like a processed picture. If you shoot in JPEG the camera will tend to apply a certain amount of image tweaking by default such as sharpening and colour adjustments. JPEG also disposes of a certain amount of data/detail from the image, whereas RAW retains everything the sensor saw based upon the exposure. JPEG is fine if you want to take a picture and not worry about sitting in front of a computer when you could be doing far more interesting things. However, in my personal opinion, when it comes to absolute clarity, RAW gives me the flexibility to apply more targeted adjustments and will also allow more post-processing before showing processing artifacts.

Final tip, sharpen only what you need to. Taking pictures of a person? Sharpen the eyes. If there is a distinct subject within your pictures, which there almost always will be, is there something in particular you can sharpen more than the rest of the image? The same goes for contrast, if you make the subject appear more bold it will improve the clarity.

  • Presentation

So you have taken the image, you’ve processed it, then what are you going to do with it? How you display an image impacts the perceived clarity and sharpness. I’ve already mentioned that different formats require different levels of sharpening but to summarise I’ll split it into print and screen.

Print. Think about the size you are printing at, what you are printing on and how far it will be viewed from. You can go with a really large print and it will still appear sharp/clear, if you are viewing it from a reasonable distance. If you are looking at the same print a few inches from your nose it won’t appear as clear. If you print on glossy paper you won’t require as much post-processed or output sharpening as you would on, say, canvas. If you add a frame to your image, the colour and depth of the frame will add or detract from the perceived clarity.

Screen. I’ve already mentioned sharpening tips when resizing for the web but in addition to that think about the content around your images. If you post them to a blog, the design around them can add or remove from the image clarity, especially the colour of the background. I find my images look best on a plain black background. They look ok on Flickr’s white background, but not quite the same as they do on my site. Also, a smaller version of your images will tend to look clearer than a full-size version. If you don’t need to crop them to 100% then don’t bother.

Hopefully all of this helps one or two people improve the clarity of their images, and thanks to Dan for the original question – my final tip is to experiment. Take plenty of pictures and play with different ways of processing them – digital photography makes it cheap to do this kind of thing. Comments and additions to this post will be gratefully received – feel free to contact me via the contact links above.

2 Responses to “Image Clarity”

  1. Gavin says:

    Hi Dan..thanks for the great feedback.

    I’ll be posting more over the next week so I’ll try to answer your extra questions. If you like you could send me a link to a Flickr image you think has lost sharpness and (if you don’t mind) you could send me the original before you uploaded it so I could take a look and see if I can spot what the issue may be.

    Thanks,
    Gavin

  2. Dan says:

    Gavin … thank you so much for the in-depth discussion on picture clarity. Although I feel I was pretty knowledgeable, your blog covered things that I didn’t know or took for granted. Amazing job.

    When you get a chance, could you provide more in-depth discussion on presentation, specifically what to do exactly for presenting pictures on the web and printing pictures. For example, in printing, I understand that the dpi is important. I use the Canon DPP default of 350dpi – is that okay – to much or too little.

    As mentioned previously, I upload my pictures to Flickr – when they are posted, they seemed to have lost sharpness. I decided on Flickr because of the need for a storage of my photos and to share them. I am disappointed in the way they look – and it has to be something that I am doing.

    BTW — great blog.

    Dan

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