Through the Looking Glass
Lenses are for life. An old cliché but it still holds true, especially in this era of digital technology. The relentless cycles of digital upgrades sees new cameras constantly released and quickly outdated. And you probably will upgrade your camera bodies in quick succession, but for lenses the choices are more complicated and it pays to think longer term. So, what lenses should you choose for night photography?
The first link in the imaging chain, and the most important part of the camera system, is the lens. Lenses are the critical component affecting the image quality of your pictures.
Lenses are a long term investment. A camera body can't fulfill its potential if the optics in front of the sensor or film are below standard.
Make it a priority to invest in good glass. Once you purchase a high quality lens it should last you a lifetime if looked after properly. You don't necessarily need the most expensive optics money can buy, either, but getting the best lens you can afford is the most economical way: lenses can generally be used on successive generations of camera bodies (even from other manufactures, via adapters) as you upgrade.
Top of the line premium grade glass can be exhorbitantly priced, but if you do some research and invest wisely you can minimise your expense. The first step is to evaluate your needs. What it is that you wish to photograph? Make your purchase decisions based on the characteristics you need, not the fancy faux-gold markings on the barrel.
Also consider the format you are shooting with. If you choose a full frame system you will need to invest in full frame lenses to cover the image area. If you then change to a system like APS-C or Micro Four-Thirds you can probably still use these same full frame lenses.
The reverse, however, may not be true - an APS-C format lens wont cover the image area of a full frame sensor and this will result in severe vignetting. However, many full frame cameras have a "crop mode" allowing the use of these lenses on full frame cameras, but only in a-lower resolution mode.
In Praise of Manual Focus Lenses
My own preference is to use large-aperture, manual focus prime lenses. This style of lens has a number of advantages over auto-focus lenses for the type of work that I like to do. This is a personal choice, based on the image characteristics and creative possibilities I'm looking for in a lens.
Manual focus lenses are suitable for use in both still photography and digital cinematography, and they also work well for filming time lapse sequences. The smooth focus action of these type of lenses, particularly the Nikkor AIS lenses I own, is very enjoyable to use. I have a set of these lenses covering various focal lengths.
Large-aperture, or "fast," prime lenses allow in a lot more light than a standard zoom lens. Most primes, especially older ones, are designed for full frame sensors or 35mm film cameras. I can also use my older lenses with few limitations on both my Nikon APS-C camera bodies and, with a Nikon to Micro Four-Thirds lens adapter, on the Panasonic GH series cameras which I use for video work.
The inclusion of an aperture ring is another reason why I like these lenses. The ring is very useful for certain applications, like digital cinematography. I have found having an aperture ring also helps to minimise luminance flicker in time lapse sequences.
Maximum Depth of Field
Many of the manual focus lenses I own have hyperfocal markings on them, which is another reason why I prefer these lenses. This feature helps you to maximize the depth of field or "zone of focus" in your photos.
This is an important consideration, particularly in low light situations
such as shooting landscapes under moonlight or starlight. When there is
very little light around to illuminate your subject you often can't see
what you are trying to focus on.
It isn't always practical to use this technique, as it generally only works at apertures of f8 and above, but it can be very useful at times to have this hyperfocal ability to help achieve critical focus.
To maximise depth of field using this method you need to align the infinity symbol to the corresponding aperture number that you have selected. Once this is set you have maximised your depth of field for that particular aperture setting.
To Infinity, and Beyond!
The majority of manual focus lenses also have a hard infinity stop. This feature makes focusing at infinity in the dark much easier than with auto-focus lenses—which generally lack this capability.
Not all manual focus lenses are created equal though. Some of the Samyang brand lenses I own don't have an accurately calibrated infinity mark. You will need to do some research about this feature for any lenses you wish to purchase, especially budget lenses.
Most auto-focus lenses can actually focus past infinity due to inherent design limitations. This isn't a good thing. They also have a hard time focusing in low light with subjects that lack distinct high contrast edges, like those found in astrophotography. Having a hard infinity stop can come in very handy in these situations.
Most modern digital cameras also have some form of "live view," a manual focus assist mode, or a range finder of some description. A live view image on the camera's LCD can help you achieve critical focus with any lens and gives you the ability to zoom into a specific area of the image to set focus. Very handy.
Live view or other forms of focus assist are also good for using auto-focus lenses in manual focus mode. However, these lenses usually lack the feel and smooth focus action present in manual focus lenses.
In Defence of Auto Focus Lenses
Auto-focus lenses do have some distinct advantages - one of them being they are much more suited to fast moving subjects. A modern auto-focus system is far quicker and more accurate at focusing on fast moving subjects than a human could ever hope to be.
Newer auto-focus lenses also usually have technically superior optical designs and use modern lens coatings and specialised glass, like fluorite and aspherical elements, with low dispersion properties. These features help to increase sharpness and contrast and reduce image artifacts such as chromatic and spherical aberrations like coma or lens flares which can degrade image quality considerably.
Many auto-focus lenses also have an optical image stabilising system built into their design. This feature can help when you are hand holding the camera. They incorporate a gyroscopic system that can give you up to 3 or 4 stops of "extra light," meaning you can reduce your shutter speed and still get sharp pictures.
For night photography this isn't such an issue though as in most situations you are better off using a stable camera platform like a tripod to prevent camera shake. This should also allow you to keep the ISO setting at a minimum increasing image quality.
Your Night Photography Lens Collection
Investing in lenses is an important consideration for all photographers. Lenses are the most essential part of your kit. If you know what style of photography you wish to pursue it will allow you to narrow down the choices considerably. I recommend manual lenses for most night photography applications.
Do some research and stay away from gear you don't really need. Keep an eye out for second hand bargains at flea markets and internet sources like Ebay. You never know, that hidden gem you're after might be just around the corner for cheaper than you think.
And stay tuned for next time, where I'll dig in a little deeper into lenses for night photography and take a look at the advantages of zooms versus prime lenses. I will also discuss the role of focal length and aperture in controlling perspective and depth of field in your images.