Digital SLR Cameras – What’s New For Military Photography

DSLR cameras are highly valued by military photographers because of their resolution, sensitivity, versatility in the field, availability of a wide variety of objective lenses and because they allow an accurate preview of framing close to the moment of exposure. Many photographers also prefer dSLRs for their larger sensors compared to most compact digital cameras, now available with image sensors the same size as traditional film formats. These large sensors allow for similar field-of-view values to film formats, as well as their comparable sensitivity.

Over 80% of the dSLR cameras sold today are models from Nikon or Canon. As a result of their predominance, an abundance of lenses and accessories are available for these two camera bodies, resulting in an excellent selection and remarkable pricing. These accessories include: objective lenses that are fast, lightweight, optically stabilized, autofocus, as well as night vision modules and other camera accessories that increase overall camera performance. Note that while there are other camera manufacturers that provide excellent products worthy of consideration for certain applications, only Nikon and Canon cameras are mentioned in this article.

Pixels: How many? How Big?

The most noticeable change in the evolution of digital SLR cameras has been the steady increase in the number of pixels that makeup the image sensor. Commercial cameras have seen the number of pixels in the camera’s sensor grow twenty times in as many years, from 1MP (1 million pixels) in 1990 to over 20MP in 2010.

Are cameras with larger sensor arrays better? Not necessarily. It depends on the application. There’s more to understanding the impact of larger array sizes than merely the number of pixels. There are two other important considerations that are considered here: the physical sensor array size and the physical pixel size.

Impact of Physical Array Size

The first dSLR cameras used image sensors that were significantly smaller than traditional 35mm film formats (36mmx24mm). As shown in Figure 2, today dSLR image sensors are available in several distinct sizes. The smallest image sensors are about 2/3 the size of the 35mm format. They are available from both Canon (known as APS-C format) and Nikon (known as the DX format). Canon also provides cameras with a slightly larger size sensor, APS-H which is approximately 28x19mm. The largest sensors (known as “full-frame” sensors) are now available in cameras from both Canon and Nikon and have the same size sensor as the original film SLR cameras, 36mmx24mm.

For cameras having an image sensor that is smaller than full-frame, a digital crop factor has been defined (also known as the focal length multiplier or magnification factor) which can be calculated by taking the ratio of the diagonal dimension of 35mm film (43.3mm) to the diagonal dimension of the camera’s image sensor size. As should be obvious by the term focal length multiplier, multiplying the lens focal length by the crop factor gives the effective focal length of a lens that would yield the same field-of-view if used on a full-frame camera. For the military photographer, the concept of having a crop factor >1 is normally regarded as a benefit. For long distance viewing, a narrower field of view is quite desirable and the crop factor provides photographers a “boost” in long-focal-length enabling them to fill the frame more easily when the subject is far away. For example, the focal length multiplier for a Nikon DX-format camera is 1.5. Using a 200mm lens on a Nikon DX-format camera will deliver the same field-ofview as a 300mm lens on a full-frame camera. However, while there are benefits for long distance viewing, the narrowing of the FOV is sometimes a disadvantage to photographers when a wide FOV is desired. For example, a 24mm lens on a Nikon DXformat camera will result in the same field-of-view as a 36mm lens, possibly too narrow for the application necessitating the use of expensive ultra-wide lenses to deliver the desired FOV (16mm in this example). Obviously, cameras having “full-frame” image sensors that are the same size as the 35mm film size, there is no crop factor (crop factor is 1).

Impact of Physical Pixel Size

In order to better understand the impact of the pixel size, compare the performance of two cameras that have the same physical array size but a different number of pixels (and consequently different pixel sizes). For this example, let’s compare the Nikon D3X (fullframe image sensor with 24MP) and the Nikon D3S (full-frame image sensor with 12MP). For the D3X, the physical pixel dimension is about 6 micron whereas the D3S has pixels that are about 8.5 micron, about 40% larger. In this example, if the military photographer is performing surveillance at a distance, identification of objects will be related to the number of pixels on target. Hence, if the same lens is used on the two cameras being compared, the standoff distance for the higher resolution model will be further than for the lower resolution camera. Explained differently, in order for the lower resolution camera to deliver the same resolving capability as the higher resolution camera with a 300mm lens, the lower resolution camera would either need a 420mm lens or the photographer would need to move closer to the target by about 25% of the distance.

As far as resolving capability goes, smaller pixels are better and the advantage goes to the high resolution camera which can use lenses that are lightweight, easy to hold and essentially “faster”. Unfortunately, more smaller pixels aren’t always the best thing for a surveillance photographer! All things being equal, as pixels get smaller in size, they also become a lot less effective at gathering light resulting in lower sensitivity for the camera. Pixel sensitivity is related to the area of the pixel, so in our comparison, the pixels that are 40% larger will likely deliver twice the sensitivity (1.4×1.4~2). This means that to obtain the same light sensitivity will require an extra F-stop or double the exposure time. Alternatively, the camera’s processor will have to gain-up the signal. (More on this in the next section). Nikon probably realized that for some photographers, more resolution isn’t always better. Adding pixels means making them smaller and the smaller the pixel the worse the light sensitivity. Fortunately, noise reduction techniques have improved considerably in the past few years, making it possible to increase resolution while keeping sensitivity about constant. So what if you applied current noise reduction strategies to an existing sensor, without adding more pixels? That’s certainly what Nikon intended with the design of the D3S, leaving the resolution at 12.1MP allowed them to increase the sensitivity for those customers that need it. For photographers who absolutely need more resolution, Nikon has the 24.5MP D3X.

Low Light Photography

For the military photographer, some of the most demanding situations occur at night when there is little ambient light, or scenes are at a distance. Today, dSLR cameras have unique capabilities and accessories are available that help the photographer make the most out of night-time imaging circumstances.

Aperture and Exposure Time

The primary factors that impact imaging in low-light are still fundamental to photography – lens aperture and exposure time. For night-time photography, since depth of field is not normally an important factor, it makes sense to select an objective lens that has the largest possible aperture. Selecting an objective lens for a specific application may be as important as selecting the dSLR camera. In fact, one may select either the Nikon or Canon body because of the specific objective lenses that are available. Similarly, exposure time for night-time imaging should be set as long as possible but still to avoid blur due to observing objects in motion or from camera jitter.

Enhanced ISO – Higher gain with drawbacks

Aperture and exposure time directly impact the amount of light that impinges on each pixel in the image sensor and affect the sensor’s output electrical signal. In addition, dSLR cameras permit the photographer to adjust the gain (i.e. amplification) of the sensor’s output electrical signal. (This is distinctly different from the ISO definition for film cameras which was to be adjusted to match the film sensitivity). For dSLR cameras, increasing the gain will amplify the sensor signal. Like all electrical circuits, image sensors are not perfect, and with the image signal, they also produce some noise in the form of unwanted random errors in the signal. Noise in digital images appears as graininess or specks of false color. To avoid too much noise, the night-time photographer adjusts the camera’s ISO to a value that is high enough to brighten the image while still maintaining acceptable image noise levels. Today, the maximum value is typically 1600, but some cameras deliver perfectly usable images at ISO 3200, 6400 or even 12800.

In addition to the standard ISO settings, digital cameras now perform noise reduction on digital images. As a result, some additional gain-up is enabled on these cameras, sometimes one step (H1), or effectively two times the maximum ISO setting, but also two steps (H2, 4 times) and three steps (H3, 8 times). This Enhanced ISO setting is now available on most digital SLR cameras. For example, both the Canon EOS-1D Mark IV and the Nikon D3S permit three levels of enhanced ISO which results in an equivalent ISO setting of 102,400! It is important to note that images adjusted as such normally have a great degree of noise and exhibit significant degradation in resolution because of the noise reduction techniques. Apparently, as with all electronic circuits at high gain, image noise can significantly degrade image quality.

Night Vision Modules

Today’s digital SLR cameras offer the photographer full control of aperture, shutter speed and ISO settings enabling the capture of excellent usable images in low light that were not otherwise possible. However, in many situations such as photographing scenes at night with very little ambient light, or telephoto photography at night at a distance, even the best digital SLR cameras simply do not have sufficient sensitivity to capture adequate images. In these situations, night vision modules are the ideal accessory.

The night vision module accessory fits between the SLR objective lens and the camera body. Simply remove the objective lens, attach the night vision module to the camera body and attach the objective lens. AstroScope night vision modules are designed to seamlessly integrate with the camera and lens combinations, maintaining all the electronic functions of the SLR objective lens (including image stabilization) via the camera’s hot-shoe. The night vision module is powered directly from the camera and conveniently turns on with the initiation of the shutter release button.

The night vision module features an automatic gain control that assures that its output is relatively constant. As such, camera settings are relatively easy to configure, as follows:
• Exposure time 1/30 sec (no need to make it shorter since the intensifier has its own lag)
• Manual aperture (so that lens F-stop setting stays put)
• F-stop at widest aperture (intensifier automatically adjusts light level)
• ISO setting adjusted to a level where camera noise is not apparent
• Autofocus Off (image intensifier scintillation can confuse autofocus sensors)
• Image stabilization On (to maintain stable images while camera is in motion)

Summary

The evolution of the digital SLR (dSLR) camera continues with impressive features being added at a steady rate. For the military or law enforcement photographer, the new dSLR camera models and new features can be quite useful for portable observation and in-the-field news gathering, both at night and during the day. Some of the benefits are:

• Image sensor arrays continue to grow in physical size, now available with full-frame formats the same as the traditional film SLR cameras.

• Pixels continue to be packed more densely, increasing overall resolution and the ability of dSLR cameras to detect, recognize and identify objects at a distance.

• Sensitivity of cameras is improving, with cameras having unenhanced ISO settings up to 12,800.

• Night vision modules are available to improve light gathering by 8-10 F-stops while still permitting electronic lens functions to continue to function, including image stabilization.

DSLR cameras continue to be highly valued by military photographers over other camera styles because of their large sensors, resolution, sensitivity, versatility in the field, availability of a wide variety of objective lenses and night vision modules.

The Lens Hood – A Brief Introduction

It is impossible to ignore the invention similar to a flower that comes in front of various photo lenses and sometimes even on the lenses. But have you ever stopped to wonder why it is present there? Those of you that had the opportunity to watch a specialized movie camera doing its thing have also noticed a device similar to an elephant ear that is put right in front of the camera. This is also known under the name of matte box.

Lens Hoods

The hoods are supposed to prevent the lens flare or glare. But when it comes to lens hoods, the range of choices is quite large. Firstly, there is the basic version. This is similar in resemblance to a lamp shade and it is utilized on the lenses which work in the larger areas of the tele zoom. Since in this case the angle of vision is very narrow, the phenomenon of vignetting (obstructing the field of view used by the lens) will not appear. Today’s market offers various types of lenses which can start from wide and continue to telephoto regions. In this case, the regular lens hoods cannot be used particularly since they can cause vignetting.

Design

The aspect of design is taken care of by using hoods which are specially created for this purpose. They are constructed by measuring the horizontal and vertical angle of vision in a separate manner. Normally, the horizontal angle is larger than the vertical one and the sunlight brought by it. This requires a design shaped as a flower or even a petal.

In what concerns the hood for every lens, this needs to be created according to the angle of the lens or else vignetting will appear. In addition to this, the lens hood also protects the lens from getting physically damaged. Some of the hoods for cameras (prosumer models) fix filters of teleconvertors directly on them. When it comes to macro photography, the short lens hoods have ring shaped LEDs placed over them. This way great lighting is assured from closer angles. The hoods mentioned are very flexible and offer great freedom to photographers. But when battery packs are included, the camera might lose its stability a bit.

Matte Box

The matte box is used especially in the video area rather than in the photo field because it can help the photographer adjust the length of the fins. Also known under the name of French Flags, the fins come with a great flexibility and freedom of movement. They are less used in the still photography and they are mainly dedicated to small environments such as studios (mostly due to the huge size of the matte box). Next to this, they also are a great place to fix plastic or glass filters.

Thus, when you decide to purchase an object of this type, you should also include a lens hood in the deal because it will provide a better quality when working with direct sunlight. This way a better contrast is created and pictures can look more powerful due to the hoods, since sunlight will not fall on the front elements of the lens.

Photography Lenses – What You Need to Know

Photographic Lenses – A perspective from an avid shutterbug

Have you ever wondered why photographs turn out different than what you saw through the viewfinder? Why is my photography blurry or out of focus? How do I capture more of the subject area in the photo? How can I get closer to the subject? Why is the photograph darker than suspected? I have had these questions over the years and have studied photography lenses so that I can select the most appropriate camera and camera lens for my subjects.

Today, with the most wonderful world of photography , and the technology at hand, it is much easier to shoot those prize photos even for the weekend shutterbug. But, if you understand even a few basics your photographs can turn out much better than you anticipated. It has become really easy for anyone to pick up a point and shoot fixed lens digital camera and take a great photo. With the influx of many high end, high megapixel cameras available for under $200.00, anybody can put memories in their pocket.

I started out shooting photography and using several types of photography lenses in the early 1980’s. My uncle introduced me to Pentax SLR equipment as he had a wholesale representative contact in Denver. I was able to purchase thousands of dollars worth of equipment for pennies on the dollar. And, so began the journey with my Pentax LX professional line of equipment. My photography lens arsenal was made up of many types such as wide angle, zoom, telephoto, macro, and standard camera lenses . I had a motor drive, high end camera flash, tripods, camera lens filters, lens hoods and more to get me started. As an athlete my first love was shooting sports which involved fast film, fast lenses, and a zoom lens. I soon fell into shooting landscapes, wildlife, and weddings. And, let me say, all for free. I loved taking pictures and giving them away to people who did not understand how to capture those prize memorable moments behind the lens.

So, what makes up the chemistry of photography lenses? How do they work and when should I use one over the other? Today it is so easy to get that all automatic digital SLR camera and lens and hope that the subject turns out as you thought it should. I think these automatic cameras are great. However, if you understand how to utilize other photography lenses in a manual mode you can still produce beautiful photographs. I actually have a Nikon D70 digital SLR camera today in addition to my Pentax LX and Nikon Coolpix pocket digital.

Photography Lenses Explained

Camera Lens Types:

  1. Wide Angle The wide angle camera lens enables the photographer to shoot a photograph when you wish to encompass more of the subject scene than would be possible with a standard lens such as a 50mm focal length. Wide angle camera lenses are typically a shorter focal length under 50mm and allow the photographer to change the perspective of the scene. A moderate focal length is about 24mm to 35mm that have apertures of F/2 or F/2.8 which allows more light in. There are also extreme wide angle lenses , called fisheyes, that can produce almost a 180 degree photo. These photographic camera lenses can be fun however, make sure you understand that the lens may produce a rounded image and the depth of field can be limited in low lighting conditions.
  2. Standard Standard lenses are typically the 50mm lenses. These are a fixed focal length and are the lens of choice on most SLR cameras . Everyone should have this camera lens . It typically will be used the most for everyday common photography. The 50mm standard lens is about what the human eye can see in the field of vision. It also produces the most relative size of the subjects and objects in the photograph. This camera lens can be one of the fastest lenses in your camera bag. It can be purchased with a low aperture of F/1.4 which will allow for very low lighting photographic opportunities.
  3. Zoom The zoom lens is my favorite lens. This camera lens gives the photographer so many options especially if you are not carrying two camera bodies with you. The zoom camera lens is not limited to one focal length but has movable elements in the lens that allow for multiple ranges. Zoom photographic lenses are available in many sizes but the typical lengths give you anywhere from 35mm – 70mm and 80mm – 200mm. I recommend these two lengths for the weekend hobbyist so that a full range from 35mm – 200mm can be achieved. These lenses can be expensive especially if the aperture is under F/4.0. They are typically not used in low lighting conditions or with motion photography unless you are shooting in daylight with sunny conditions. For most photography hobbyists, the 80mm – 200mm works great for sideline photographs and has enough focal length to capture images such as wildlife from a distance.
  4. Telephoto Telephoto camera lenses have a focal length that is longer than a normal 50mm lens. The longer the length of the telephoto camera lens the more magnification you can get and the closer you can draw near to your subject. These camera lenses differ from the zoom in that they are fixed and cannot provide the photographer a range of lengths. Most telephotos are used where the subject is static and situations where you are restricted to keeping your distance. They usually come with a smaller aperture somewhere around F/4.0. Careful selection and use must be made when using these lenses as they can be heavier and blur photographs with the slightest movement. I would recommend a tripod or monopod for use with lenses longer than 200mm. They are absolutely great for sports and wildlife photography. I have used anywhere from 100mm to a 500mm mirror telephoto. The 500mm mirror lens was really nice when shooting at an air show.
  5. Specialty There a couple of specialty camera lenses that I’ll talk about. The first photographic lens that is a must for close- up photography is the macro lens. This lens can come in a few focal lengths that are typically less than 100mm. The macro camera lens enables the photographer the ability to shoot subjects extremely close-up such as flowers, insects, and commercial products. These camera lenses are really fun and can produce beautiful images that fill the frame with wonderful color and detail. I have done a lot of macro photography and recommend that a tripod be used when shooting these subjects so that blurring is limited. These lenses can also have lower apertures so that long exposure under low lighting can be accomplished. The other type of specialty lens is the perspective control lenses that will take close up photographs and keep the subject sharp in focus and prevent the depth of field from distorting the subject. I have not used these types of lenses so I cannot give you a real life example. However, for most non-professional photographers this lens may not be worth the investment. Finally, I will mention the 2x converter. This photography lens cannot stand alone but augment another lens by boosting the focal length by two times it’s standard length. You simply add it between the camera and your lens of choice and the optical mirrors magnify the image by two. I use this often outdoors shooting sports on sunny days where I have a bunch of light. This will boost my 300mm zoom to 600mm. And, I can get really close to my subjects from the sidelines.

Photography lenses today provides the shutterbug an array of opportunities for photographic design. Depending on the type of photographer you are, it will determine the types of camera lenses you put into your camera bag. I would suggest that everyone has at least a mid-range zoom. If it is the only lens in the your budget at time of purchase, you can add other camera lenses later. The 35mm – 70mm would be my recommendation. If you are going to shoot athletics you will most likely be on the sidelines or in the bleachers and will need up to a 300mm telephoto or zoom. Depending on your budget I would suggest a lower aperture but nothing more than F/4.0.

Have fun and remember that you can take oodles of pictures today and test your photographs much easier with digital SLR photography . If you don’t like your results, delete them. Then, go out and take more pictures!

To your photographic success.