Choose the right manufacturer
A specialist's product will incorporate all their experience
Always choose a specialist manufacturer or a world class brand that makes its own products. That way you can be confident that the product has been thought through, well designed and will perform well.
Many brands simply buy generic far-eastern items and put them in their colours and packaging. Product performance is often poor, workflow and user guides badly written and the product poorly designed.
If you choose a specialist manufacturer you will benefit from all their research and expertise in that field. Their business will be focused completely on inspection and will provide you with the best products and the best support.
So what is an inspection camera
A device for viewing into hard to reach places
An inspection camera comprises a small camera on the end of flexible pipe with a handset and screen that allows you to see into hard to reach places and to locate problems and issues much faster and easier than you would without the camera.
The greatest benefit of an inspection camera is the amount of time it can save. Inspection cameras can also save a lot of cost, not just through time saved finding issues quickly or avoiding equipment strip downs but also by avoiding damage to property in the process.
What are they used for?
Typically looking into dark place - under floors etc
Inspection cameras can be used under floors, within walls and cavities, in ceilings, roof voids, in drains, pipes and flues, even chimneys, gutters and vents and all types of machinery and vehicles. Not all cameras will perform well in these situations; there are many factors that affect the quality of an inspection camera.
- Locate cables, pipes, valves and similar
- Locate the source of leaks
- Find blockages, damage and corrosion
- Find broken parts
- Inspect machinery and manufactured goods
- Find missing items
- Locate pests
- Show customers and colleagues issues found
- Hundreds of uses in industry
- Many uses around the home
- DIY enthusiasts
- Maintenance staff
- Plumbers, heating and air conditioning engineers
- Mechanical engineers
- Building inspectors
- Property maintainers
- Vehicle mechanics
- Service staff
- Pest Controllers
There are a number of inspection cameras on the market these days, ranging from very expensive models from top brands and quality solutions from specialist companies through to low cost generic branded items made in the far-east.
Like most things there are huge variations in performance and this guide should help you make an informed choice to get the right product for you.
What performance should I expect?
Being able to see at least 1m in total darkness
Inspection cameras allow you to see into hard to reach places, places where you cannot easily see with your own eyes and which are small and hard to access with a normal camera or smart phone.
Inspection cameras are not designed to perform well when looking round the room, you don’t need an inspection camera for that, you can see what’s around you with your own eyes, instead they should be designed to give you a good picture in dark hard to reach places such as under floorboards or within cavity walls.
An inspection camera should do well at allowing you to see into places you can’t.
How to choose the best inspection camera
Follow the advice in this guide
An inspection camera comprises three main elements.
- The camera
- The flexible pipe
- The handset
The way the product performs depends on all three elements and you should consider all three elements when making your choice.
Should be less than 10mm
Historically endoscopes and borescopes were developed for medical and precision engineering applications such as the inspection of gun bores, hence the name borescope.
These operated with fibre optics and a light source to enable the use of a small and flexible pipe for such applications. At the observers end images might be viewed manually through an eye piece or via a camera connected to a TV monitor.
As technology has progressed smaller and smaller image sensors and cameras have been developed which have created opportunities for fully electronic systems, known as inspection cameras. The mobile phone revolution and the huge volumes involved has driven the miniaturisation of camera technology and this has also driven down the cost.
Utilising mass produced and low cost image sensors has made inspection cameras more affordable but because mobile phones do not have the same size constraints these early camera pipes tended to be quite large, with diameters of more than 15mm.
Smaller camera technology has been developed but remains expensive, so the smaller the camera, the higher the cost of the image sensor and of all other parts involved in the camera for that matter.
The smaller the camera, the smaller the optics and the higher the cost of these, and the smaller the camera, the more precision components are needed and again, these cost more.
In addition, larger camera systems are easier and quicker to manufacture, with better yield rates and require less skilled workers so again they are cheaper.
Cheaper camera systems are often bought in as modules from specialist manufacturers and assembled by non-specialist companies using low cost unskilled labour in less than ideal conditions. This results in low cost cameras which are often unreliable and with contamination and dust within their optical systems.
In the case of professional solutions the tiny camera heads are assembled and focused by hand in clean room conditions, so the smaller they are the more specialised the company that makes them, and the higher the quality and more reliable the finished item.
The other factor, not often considered is the size of the supporting components. On its own an image sensor needs some form of image processor to scan out the data from the sensor and transmit it to the receiving handset in either analogue or digital form.
Some image sensors and image processors have been combined into a single piece of silicon small enough to enable the construction of tiny cameras, but for other solutions, having a small image sensor is just one part of the equation and the manufacturers also have to find a processor that will fit inside their target package diameter.
Cameras with overall diameter below 4mm have been developed and in time even smaller cameras will be possible, although for everyday applications and looking within petrol engines a camera head around 9mm is fine but if it’s necessary to look inside diesel engines then a camera diameter of less than 6mm is preferable.
Image sensors and resolution
Should be right for the application
Technological limitations and physical constraints all give rise to compromises when it comes to miniaturisation but image sensors continue to get smaller and smaller and the next revolution will be the introduction of affordable full HD inspection cameras, made possible by the next generation of image sensors with development driven by mobile phones and the proliferation of cameras within our world.
At this time the cost effective image sensors used for inspection cameras offer resolutions of 320 x 240 pixels (QVGA) and 640 x 480 (VGA). On paper these look like low resolutions, especially in a world where we’re are all used to large megapixel image sensors on our mobile phones and cameras with the ability to capture fantastic video and photos at the touch of a button, however in context these small sensors can deliver excellent image quality. The key is tuning the handset and the camera pipe to give the best possible picture.
To achieve sub 6mm camera pipes, image sensors need to be very small but also allow enough space for an LED to fitted into the package as well. For such small sensors, usually less than 2.5mm square, each individual pixel becomes very small. The smaller the pixel and the less light reaches it, therefore such sensors tend to me less sensitive.
As technology has progressed miniature VGA sensors have also appeared, but to get more pixels in the same size package means each pixel must be smaller which results in less light per pixel. Fortunately, new image sensor technology and substrate materials have improved sensitivity and so some VGA image sensor provide excellent performance, but again a lot of effort is still necessary to tune the sensor and display systems to give the best possible image.
For applications where cameras are required to operate in total darkness such as pipe inspection the sensitivity of the camera plays an even more important part in the system performance and the quality of the images provided.
Developers often compensate by trying to provide more light with more LEDs, but this uses more power and results in bulkier cameras. Inevitably, to make an image sensor more sensitive to light it is necessary to use larger pixel sizes and so the overall size of a more sensitive image sensor increases.
Fortunately the size of the camera head in pipe inspection systems which need to be very sensitive tends to be less of an issue so larger sensors are more acceptable for these cameras.
New HD technology means that sub 10mm camera pipes with full HD image sensors will soon be possible, however VGA resolution is the limit for analogue video signals which means HD cameras require digital links and with these come noise issues, distance challenges and increases in transmission components and costs, so at this time VGA and QVGA inspection cameras rule.
Two test images, on the left QVGA and on the right, VGA, four times the resolution of QVGA, however both cameras served their purpose and provided adequate images, the QVGA being 5.5mm in diameter while the VGA camera is 8.5mm in diameter.
A close range 5.5mm QVGA provides useful pictures of an M3 thread including the brushed metal
Generally 640×480 pixel (VGA) resolution is perfectly adequate for inspection cameras and when part of a well-tuned system will deliver excellent picture quality, after all it is not long ago that we were using home video cameras with this resolution.
Of course the resolution of an image sensor is one thing, but lens choice and camera head design also plays an important part in the quality of the final image.
Focal length - a compromise
Close up or general use
The laws of physics, the very small size and single lens assembly of inspection cameras lenses means that no one camera will be suitable for every application.
If you need to get into small spaces such as the cylinder of an engine then a small camera fixed for close range would be the best solution.
For more general applications, cameras with focal distance set from 20mm to infinity are acceptable because they’re generally used to view larger objects in bigger spaces.
Of course it is possible to adjust the focal distance of a camera so it can see very close objects indeed, however in so doing the depth of field reduces dramatically so that beyond 1mm or so everything else is out of focus.
Images of a dead fly using a 5.5mm close range camera, adjusted for a very close view showing just what is possible with a small camera,
however, as the image of the fly shows, depth of field is lost.
These images, taken with a standard 8.5mm VGA camera pipe and a similar camera adjusted for very close range dramatically shows how depth of field is lost if focal distance adjusted too much. However, note that the printing spots can be seen on the pen and the laser printed test image.
Images taken with a standard 5.5mm QVGA camera of the inside of a coked up engine. Damage to the piston and valve seal can be seen as can be scoring on the sides of the cylinder walls.
These images highlight what is possible with a modest 320×240 pixel camera
In practice such close range inspection cameras are not practical with small diameter systems and the focal distance for such cameras is set at a compromise distance to allow the user to see the object of interest in reasonable detail whilst still being able to view the bigger picture in focus.
The camera should use the correct type of sensor
Low light sensitivity
To make a pipe with a camera and LED on the end that will allow you to look around a well-lit room is one thing, but to make a camera and LED that performs well in total darkness and the sort of real-life situations where it would be used is quite another.
For an inspection camera to be any good it should allow you to see a reasonable distance in total darkness. Up to 2m is considered very good and in such circumstances if you can see an object of interest you can then move the camera toward that object to get a better view, if of course the camera pipe is long enough.
Image taken of a test object, mounted 2m away within a light sealed black test box in total darkness
Of course a camera detects light that is reflected towards it, either from incident light or from it’s own LED. If viewing a completely dark void it is unrealistic to expect any inspection camera to see anything as there will be no objects to reflect back the light. The human eye and proper cameras and smart phones can adjusts to such circumstances by adjusting the size of the pupil and allowing more light to enter the camera, but of course an inspection camera system is fixed and cannot change.
So to improve performance in complete darkness the professional inspection camera manufacturers use higher sensitivity sensors and also use software to enhance the image to enable distant objects to be viewed.
For particularly demanding applications such as drain and pipe inspection super sensitive image sensors should be used as these provide excellent images in near total darkness and reduce the need for additional lighting, thereby reducing power consumption and camera size.
Quality not quantity - more LEDs is not better
Like cameras, not all LEDs are equal and more is not necessarily better. For example one single ultra-bright LED might give a far better image and range than four or six low cost inferior LEDs.
Similarly, it is not the number, but the brightness and field of beam of the LED that affects the performance of the inspection camera. To perform well an inspection camera requires a bright light source but beam width is also a factor.
LED’s with a beam narrower than the field of view of the camera will result in dark areas around the edges of the images. Similarly LEDs with beams much wider than the field of view of the camera will waste light energy shining on areas the camera cannot see.
Also, multiple LEDs can often create strange patterns where light intensity is increased where their beams overlap.
The LED and the camera should be closely matched to give the best performance.
A single bright LED when combined with a sensitive image sensor will often out perform a regular camera with multiple LEDs.
The Flexible Pipe
Size should suit the application and be under 10mm
Many inspection cameras have large camera heads ranging from 10mm to 18mm and even bigger. These enable the manufacturer to use low cost image sensors although this doesn’t result in any better quality as generally such cameras will be VGA resolution or less.
Of course the larger camera head means that a much larger hole is necessary in order to get the camera through and in many cases the space beyond the hole will be small making such cameras effectively useless.
As already mentioned, the smaller the camera head, the smaller the sensor, but for nearly every application a camera smaller than 10mm will enable you to get into very tight spaces.
Camera Head Design
Should be waterproof, chemical resistant and robust
Simple low cost cameras are made by pushing a ready-made camera module with a camera surrounded by several LEDs into a tube shaped head and then covering that with a round plastic lens cover.
The biggest problem with this design is often reflection of light back into the camera. With poor quality designs of this nature light from the LEDs passes through the same plastic lens cover that allows light to enter the camera, but because the plastic is not perfectly clear, the front and back surfaces of the cover reflect back some of the LED light and some of this enters the camera lens causing a whitening of the image.
Good quality versions of this design can overcome this issue but it something to be aware of when buying a low cost camera and this whitening can sometimes be so bad that in dark conditions that the brighter the LEDs are the whiter the image until almost nothing can be seen at all.
Often such camera designs use cheap and poor quality LEDs so that even at full brightness in dark conditions the camera can only see maybe half a meter ahead, not much use under floor boards or within cavities or similar. These inspection cameras are fine looking round a room in daylight but try using them where you need to and suddenly you discover they won’t do the job you need them to.
By changing the plastic lens cover to a glass cover the whitening issue can be improved, however there’s another problem with both these designs. Both the plastic and glass will scratch quickly and easily and as a consequence performance of the camera goes down very quick with use.
The solution is to use a crystal lens cover although this increases the cost but because of its greater clarity and improved scratch resistance it does improves the performance on both fronts.
An even better head design is to have a completely separate LED and camera, however this requires precision components and more time and skill in assembly thereby increasing the cost. But with this design, no incident light from the LED will enter into the camera lens other than through reflection from the objects being viewed as the two are optically isolated by the structure of the casing.
Such designs are usually more robust that the simple tube structure and far more reliable and typical of more professional equipment.
Flexibility of the camera pipe
Should be a compromise between rigidity and flexibility
The camera pipe is the main control for steering your camera. Too stiff and you won’t get it around obstacles, too flexible and you won’t be able to direct or push it. Like the focal distance this is a trade-off, this time between flexibility and rigidity.
Therefore avoid the really heavy and strong camera pipes unless that specifically meets your needs as these are hard to bend and manipulate and equally difficulty to get through and around things.
Likewise, a camera designed to get in to small spaces in and around machinery and engines will need to be more flexible than one used for applications within a property and a camera pipe used for drain and pipe inspection will need to be incredibly strong and rigid to allow it to be pushed through pipes.
It is therefore very much a case of choosing the right camera pipe that’s been designed for the type of application you have in mind.
Waterproof and chemical resistant
Should work in gasoline, diesel and all fluids found in vehicles
Whilst it may not be the normal way your camera will be used, it does help if it is waterproof for those occasions when it may get wet and certainly for all types of plumbing use this is an absolute must.
For automotive mechanics and other engineering applications chemical resistance may be necessary. Whilst most cameras will not be exposed to harmful chemicals for long periods of time they should be able to withstand a small level of exposure without any adverse effect.
Camera Pipe Reliability
Use a digital oscillator instead of a low cost crystal for reliability
Inspection cameras are a precision instrument and should be treated with respect but inevitably they will get a lot of abuse in the real world, being shoved in to holes in walls, under floors, down drains and so on.
The design and construction of the camera pipe needs be such that it can put up with a reasonable amount of abuse. The camera should withstand several drops of at least 1m on to rough concrete.
The internal components should be sealed, not only for mechanical strength but also for waterproofness. In addition, the camera head circuitry will require some form of oscillator to work, however cameras using low cost crystal oscillators will break even with the simplest of impacts because the crystal will not withstand the shock.
The best cameras will use solid state oscillators for reliability.
The camera head shown here had been dropped 100+ times on to rough concrete during reliability testing
The inspection camera pipe itself, whilst being flexible must also be strong and reliable and put up with a lot of abuse before failing. If the camera head gets stuck, the camera pipe should be able to withstand a certain amount of stretching and the internal wiring have sufficient slack to avoid being snapped when a clumsy user pulls too hard to try to get the camera back.
Attachments and Accessories
Should include longer pipes suitable for drain inspection
Whether included with a unit or supplied separately, attachments such as a mirror, hook and magnet are really useful and add another dimension to an inspection camera, allowing you to quickly recover metal items with the magnet, pull cables with the hook and look round corners with the mirror.
As we’ve said already, there are variations in the quality and design of all these products and so take care to consider whether an accessory is fit for purpose. A weak magnet or a hook that is too small, or worse still a mirror that you can’t see with will be ineffective.
We’ve even seen attachments that just push on without any form of fixing – one good pull on a cable or a heavy object with a magnet and the attachment comes off!
On its own an inspection camera is a really useful tool and one which will save you a lot of time and cost whether in your work or for DIY jobs around the home. The addition of accessories and attachments will expand that range of uses from longer camera pipes, extension poles and extra long drain inspection attachments, choose a camera that offers you all these benefits.
Screen size and image contrast
Larger screens are not always better
The size of image affects how the human brain interprets the image and perceives the quality of that image. For example a 640 x 480 image on a 2.4” LCD will often look better than the same image on a 3.5” LCD and undoubtedly such an image will not look great when blown up on a high resolution computer screen, especially when we are so used to high resolution images all around us.
However, for the purposes of inspection and more importantly being able to see into hard to reach places, which is the primary purpose of an inspection camera, a small screen works well and causes the brain to perceive higher resolution than a paper specification might suggest.
As already mentioned, careful matching of a camera and a display system are necessary to provide the best quality image and the brain perceives images with strong contrast as containing more detail. Unfortunately, many cameras are not matched and provide only adequate images. Also, high contrast images limit the viewing range of camera in that the distance fades in to darkness obscuring far objects.
To provide better long range visibility some systems use image enhancement to enable father objects. The camera can then be directed towards them to help the user locate the object they are looking for and the brightness adjusted accordingly. The bigger the screen therefore does not mean the better the image, it just means the same resolution of image is displayed on a larger screen which may possibly result in a worse picture.
One handed operation and general ease of use
Choose an inspection camera that’s been designed to fit in your hand and is comfortable as you might need to be using it in an awkward position or for some time. Ergonomics matter yet many manufacturers forget about this aspect of their product.
Make sure the camera can be operated with one hand because you will definitely need the other hand to guide and control the camera pipe.
If you have to let go of the camera to press a control or take a photo or video then chances are that the camera will move and you won’t get the shot you wanted.
Even inspection camera handsets with multiple buttons can be difficult to operate with one hand because your fingers and thumb may not reach the controls whilst holding the handset.
A well designed inspection camera will have all the controls within easy reach of the fingers and thumb with menu options and controls that make sense.
Inspection camera workflow should follow frequent operations and controls should be consistent, for example, the most frequent options are likely to be zoom and LED brightness whilst the most frequent menu option will be playback of recordings so these options should be at the highest level.
Some cameras have single function buttons for these operations making it easy and obvious whilst others can be more complicated and some lower cost generic items have horrific and inconsistent workflow as they tend not to be designed in the west.
Professional cameras should be able to record photos and video
For DIY applications, just being able to see into an inaccessible space is useful enough but as a professional using the tool for work the ability to record photos and videos is worth the extra cost.
It allows you to support your findings, perhaps justify extra expenditure by showing customers evidence of a problem whilst having the added benefit of also being able to send the information to colleagues.
Of course, as already discussed the small size of the camera head limits the resolution of these cameras generally to VGA and when viewed on the handset of the inspection camera these should look good enough to understand what’s being viewed and to explain for a customer an issue.
The ability to pause, fast forward and rewind during video playback helps when showing others the issues that have been found.
A recording camera with built in memory will work straight out the box and there’s no need to buy an extra SD card or the worry about having a card to hand when you need one. Whilst most inspection cameras do not offer recording, of those that do, hardly any have internal memory so this is a real plus point.
Time and date and data stamping
Some manufacturers have included extra features such as audio for video recordings and annotation for photos. The ability to compare live images with a saved reference image is particularly useful but only available on one or two models.
For recording cameras, time and date stamp is essential so you know when the recording was made but also very useful is the ability to embed customer details such as name or reference number, particularly useful for recording job references or car registrations on photos or videos.
The ability to view and playback on a TV can be helpful, but the majority of extra features are gimmicks and the main emphasis should be on image quality and the camera pipe.
Wi-Fi and USB inspection cameras
Waste time setting up with poorer images
There are a number of wi-fi based inspection cameras on the market that make use of the screen on a smart phone, laptop or tablet. These are just gadgets and whilst on paper may suggest higher resolutions they don’t deliver the image quality or frame rates of analogue camera systems and fundamentally setup takes so long and is so often hit and miss that any time savings to be made using the camera are lost by the time it takes to get the wi-fi working. With a regular inspection camera you turn it on and within seconds will be able to view into the hard to reach place.
Similarly, very low cost USB cameras, basically nothing more than a web camera on the end of a long wire have several disadvantages. Firstly they require a laptop to operate and again the same issues apply as with a wi-fi system and there is also the inconvenience of needing to have a laptop with you and in the environment where the camera is being used which could be outside, in an attic, under floorboards or any sort of dirty and dusty environment. Secondly, to make them cheap they are usually just a camera on the end of a very flexible wire, so offer no ability to control or direct the camera and unless gravity is on your side they aren’t a lot of good.
For a few pounds more, invest in a proper inspection camera and get the time savings and performance that you would hope for from a professional piece of equipment.
Take confidence from other users
It’s often hard to tell from what other people say about products, after all everyone has a different opinion and standards but it’s worth reading testimonials and considering if you can find out if larger companies, government bodies and similar organisations use the cameras you’re interested in.