"There are few things you have to consider that will enhance the clarity and quality of your images, especially if you're shooting handheld. The term "tack sharp" is used in photography to represent the absolute best clarity of detail in an image. Sharpness is affected by two elements: focus and contrast. When you have an image with crisp focus and well attained contrast, and no visible blur when looking at it at pixel level, it is considered to be "tack sharp". If you are thinking you can correct the clarity of your images by using the Photoshop ‘sharpening and contrast’ tools to enhance your images, you may want to rethink that approach. If you don't have a “tack sharp” image while photographing in the field, no amount of post production work is going to produce quality contrast, make a blurry image sharp or create fine detail where there is none. Therefore, it is important to know how to capture "tack sharp" images straight from the source—your camera.
Why images can get blurry? Typically this is due to one of the following: camera shake while hand holding the camera, shooting with a slow shutter speed, and/or not using a fast enough shutter speed when the subject is moving. Understanding how to correct these issues is vital to creating “tack sharp” images.
What it can do to help? What shutter speed should you use? That will depend on what you are shooting--if your subject is moving or still and what type of affect you are trying to achieve (show the motion or stop the motion).
Examples of shutter speeds:
Stop race cars or pro-athletes 1/2000 - 1/4000 sec.
Stop a bird in flight 1/1000 - 1/2000 sec.
Stop action at gymnastic meet 1/800 - 1/1500 sec.
Still life or portraits 1/125 - 1/250 sec.
Landscapes 1/20 - 1/100 sec.
Waterfall on a cloudy day - velvet smooth water 1/2 - 1/30 sec.
City lights at night 8 - 30 sec.
Low light indoors with no flash & no movement 5 - 30 sec.
THE RECIPROCAL RULE
It is perhaps the most used “rule of thumb” in photography. It is used to determine the slowest shutter speed you can safely use while hand holding your camera and still prevent camera shake. It states that when hand holding your camera, the shutter speed should not be slower than the reciprocal of the effective focal length of the lens you are using. So, if you have a 55 mm lens, then the reciprocal of that would be 1/55, which means that the slowest shutter speed you should use would be 1/55 seconds.
200mm lens: Shutter Speed (SS) >= 1/200 sec.
100mm lens: SS >= 1/100 sec.
70mm lens: SS >= 1/70 sec.
Much has been written regarding the reciprocal rule, some positive, and some negative, but if you use it as a guideline only, a starting point from which to base your shutter speed decisions, then this rule should serve you well.
Be sure to factor in the following questions when making your choices:
1. How steady are your hands?
2. What method do you use to hold the camera steady?
3. Do you have vibration reduction or image stabilization on your camera or lens?
4. Are you using a full frame sensor or a cropped sensor?
5. Is your subject moving or holding still?
Based on these questions, you can make few adjustments. If there is not enough light and the aperture is close to being wide open, then you might have to choose between opening the aperture wider or slowing the shutter speed. Start from the maximum(widest) aperture, before going down, especially for moving subjects.
Effective Focal Length
The focal length of a lens is based on the size of 35mm film. If the digital sensor in your camera is full frame (the same size as 35mm frame) then the "effective focal length" is the same as the markings on the lens. However, if you have an entry-level DLSR you will have a smaller sensor. If this is the case, you will have to do some math in order to calculate the “effective focal length". Consumer grade Nikon cameras usually have a 1.5 crop factor, while Canon's have a 1.6 crop factor. Check your camera's manual to see if your camera has a crop factor. If you have a crop factor, you need to multiply the reciprocal of your focal length by the crop factor in order to get your minimum shutter speed.
Nikon 200mm lens: (200 x 1.5) SS >= 1/300 sec.
Canon 200mm lens: (200 x 1.6) SS >= 1/320 sec.
Nikon 100mm lens: (100 x 1.5) SS >= 1/150 sec.
Canon 100mm lens: (100 x 1.6) SS >= 1/160 sec.
Another way to increase your chances of getting “tack sharp” images while hand-holding your camera is to use the continuous shooting mode on your camera to take several shots in rapid succession. This will increase your chances of having a least one shot that is “tack sharp”.
IMAGE STABILIZER (IS)
Using Image Stabilization allows you to use a slower shutter speed. Some lens manufactures, and or lens review sites, say you can shoot at speeds 2-4 stops down from the hand held rule of thumb, depending on the lens. That means that if you shoot down 4 stops (16 times longer), you would get similar levels of sharpness with IS on at 1/8 sec. as you would at 1/125 sec. with IS off.
Examples: With IS/VR
Full frame & 200mm lens: SS >= 1/200 sec. 1/100 - 1/60 sec.
Nikon 200mm lens: SS >= 1/300 sec. 1/150 - 1/75 sec.
Canon 200mm lens: SS >= 1/320 sec. 1/160 - 1/80 sec.
But if you believed you have an extremely steady hands, of course you can go below 1/60sec with IS on. Few times, I did shoot at 1/40 in weddings mainly because;
1. It was in a very bad lowlight condition.
2. Because I wanted to keep sharpness and clarity of everything in the composition.
3. And I don't want to compromise getting image noise if I chose to jack up my ISO.
You may say, I forgot about the Aperture. It's always associated with the lens.
What is the primary function of a camera lens? It collects light. If there is no light, you have no image being captured by the image sensor.
In simple terms, Aperture is a unit of measurement that defines the size of the lens opening which allows a certain amount of light to enter, based on the size of the opening—the larger the aperture opening, the more light that is allowed to get through.
It is defined by the focal length* of the lens divided by the diameter of the lens, and is recorded in "f-numbers" (f-number = focal length ÷ lens diameter).
*Note-Focal Length: It is the distance from the middle of the lens to its focal point (convergent point when parallel rays of light strike a lens focused at infinity).
Normal lens is considered: 50-55mm
Less than 50mm: a wide-angle lens (small focal length with a wide angle of view)
More than 55mm: a telephoto lens (long focal length with a narrow angle of view)
It is not measured in "units" of measurement like inches or millimeters, but rather it is a relative number. For example: f/8 represents a number that is 8 times the "effective" aperture diameter, which is called the "entrance pupil".
Put another way, if you have a 100 mm lens (100 mm focal length), with an aperture of f/8, the "entrance pupil" will be 12.5 mm. (100mm ÷ 12.5mm = f/8)
Compare that with a 150 mm lens (150 mm focal length), with an aperture of f/8, the "entrance pupil" will be about 18.8 mm, but both lenses will give you the same exposure at f/8 when photographing the same subject (150mm ÷ 18.8mm = f/8).
“Sweet Spot” / Optimal f-number
All lenses have an aperture setting, or range, that is called a "sweet spot" for sharpness. Each lens is different, but as a general rule of thumb, the sharpest images are taken with the aperture 2 f/stops down from the widest opening. So if your camera has a lens which is wide open at f/2.8, then the "sweet spot" will be two stops down to f/5.6.
But what many photographers don't realize is that you will also get "softer" images with the aperture at its smallest opening, due to diffraction (light rays get slightly "bent' as they squeeze through very small apertures, resulting in you getting progressively less sharp images beyond a certain aperture). When you use smaller apertures (larger f-numbers) to achieve a greater depth of field, at some point the aperture size will cause some softening due to the effects of diffraction.
Top quality lenses are vital to creating “tack sharp” images. This usually means buying the Pro-grade lenses by the manufacturer of your camera. There are a lot of good third party lenses out there and some will give you some good results. But if you are looking for better than good, then your best bet is to go with the camera's brand name. There may be a few exceptions, but very few.
Top quality lenses are much more expensive and there is a very good reason for that--they are that much better. They will generally give you better image quality, faster auto focus speed, better detail, sharper focus at all apertures and focal lengths (if it is a telephoto lens), minimal image distortion, better quality of color, flare resistance, vibration correction, and build quality.
Although, there are more other ways of getting that tack sharp images, it's up to you what really works for you.
Brad Sharp has been a working artist almost his entire life--beginning in the 5th grade. His parents signed him up for special art classes at a downtown Portland art museum and that was all the catalyst he needed to move forward.
He has worked as a freelance Graphic Designer and Illustrator, an Art Director for a nationwide advertising company, a computer programmer, a photojournalist for a local newspaper, and now as a stock photographer and a photography instructor. He shares his knowledge of photography by teaching photography classes for Utah Valley University - Continuing Education. His love and passion for photography shines through to his photographs.
CLICK HERE to visit him.