Criteria One: How Big Can You Print?
Pixel Size has a direction relationship to how big you can print:
The first thing that limits print size is the megapixels of the camera. When you print a photograph it is normally printed at 300ppi, this can be expressed as true photograph quality. The following shows the relationship between megapixels and true photographic quality:
- 3 megapixels 6.82″ x 5.12″
- 4 megapixels 8.21″ x 5.44″
- 6 megapixels 10.02″ x 6.67″
- 8 megapixels10.88″ x 8.16″
- 10 megapixels 12.91″ x 8.64″
- 12 megapixels 14.30″ x 9.34″
- 16 megapixels 16.40″ x 10.88″
- 35mm scanned 17.93″ x 12.06″
This assumes that the photograph is being view from 25cm, some argue that if a photograph is considerably larger then it would not be viewed from this proximity and therefore could be printed at 150 ppi and have acceptable quality. If you feel comfortable with this theory then this would double the size of the print.
Criteria Two: Pixel Quality
Pixel quality can have a big impact on the quality of your photograph:
The second impact on the quality of your images is the size of each individual pixels on your sensor. Pixels are measured in microns as are light rays. The average light ray is .7 microns and an ideal pixel size is 6.8 microns. So if you do the math this size pixel can capture almost 10 light rays. Why is this important? Well cameras are not perfect nor are lenses and with 10 light rays this sensors pixel can filter out errors that effect the quality of the image.
So as the pixels becomes smaller the quality of the image decreases, bad quality has its biggest impact when you try and enlarge the original photography.
The diagram below shows the pixel pitch or micron size of the pixels on each cameras sensor. Ideally you are looking for 6.8 or higher. Between 5 to 6.8 the quality appears good until you begin to increase the size of the image beyond its normal size.
Criteria Three: Sensor Size and Larger Lenses
Large sensors and the lenses that go with them improve quality:
As you can see from the chart above the larger the sensor the more likely you will get a good pixel size and therefore good picture quality. Larger sensors and the larger lenses that go with them produce higher quality images. Why are they higher quality? Well they have a higher dynamic range, increased ISO low light performance, less noise, and less diffraction. In addition to this as the sensor gets bigger so do the lenses this means the depth of field decreases, wide angle lenses become wider and telephoto lenses are less magnified.
Criteria Four: The Proprietor Black Box
Proprietor software and hardware are hard to evaluate:
How the camera manufacture chooses to design their processor and how it interelates with the cameras hardware is impossible to evaluate. It is a black box that can only be evaluated by pouring over photographs that have been shot in a variety of situations. Perhaps here you will have to turn to trusted sources on the internet. I would suggest sites like Digital Photography Review but avoid popular consumer sites, which rarely assess this aspect of the camera.
The newer the camera, of course, the more advance the sensor will be and the more advanced the firmware and software. So it does pay to check the release date on the camera and make sure it is new technology, as some cameras can stay on the market three of four years before they are replaced. Again Digital Photography Review has a timeline you can search to find the release date for all cameras.
Criteria Five: Focus
How a camera focuses is an underrated but very important quality issue:
Do not underestimate the importance of the auto focus on your a camera. The auto focus is what keeps your images sharp and their are a few things you need to evaluate:
- Make sure you understand how many focusing devices the camera has and remember they are not always the same. For example the 5D Mark II has only one true focusing point on the camera, the other points are contrast focus points.
- Focusing can be done either in colour as in Nikon cameras or in Black and White like Canon cameras. They both do different things to the quality of a photograph.
- There is also a difference in the number of focusing points in a camera. For example the 5D Mark II has a nine point focusing mechanism and the Nikon 700D has 51points.
Criteria Six: Camera Features
A camera that’s hard to use effects the quality of your photography:
As the camera becomes more expensive it has has more features, so you will need to evaluate how important some of these features are to you. It would be a mistake to assume if you are not using it now then you probably do not need it. Rather you should examine why these features are used by others and decide over the life of the camera (3-5 years)which ones you will likely grow into. Here are some features you might want to consider:
- Alloy framing with dampness and dust protection. This feature will allow to more comfortably shoot in transitions weather conditions and dusty sites.
- Fast frames per second will allow you to not only shoot sports but even assist you in getting a good portrait shot as the face changes rapidly.
- Video capacity of the camera and its audio connection.
- ISO sensitivity (this is a black box issue)
- Size of the LCD monitor
- Are all the adjustments easily reachable on the camera or are they hidden in awkward places in the menu system.
- Is the flash system easy to use. For example Nikon builds in a command system into the camera, which controls the flash and all camera settings. No need for light meters and making adjustments to the camera.
- How heavy or large is the camera, this will effect how often you take the camera into the field.
- Single of Dual memory bays. These can be used in a number of ways, backup, RAW/JPG split or extra on board memory.
- The ability to take high dynamic range pictures depends a great deal on your expose bracketing. Some feel three brackets are enough. I have found a minimum is really needed. Nikon for example allows you to exposure backed up to 9 exposures one stop apart.
Criteria Seven: Lenses
The “glass” (your lenses) is everything:
When choosing a camera manufacture your first piece of research should be what lenses are available for the camera and what is the quality of those lenses. For example in the half frame and full frame market Nikon and Canon have more lenses than any other companies. In addition to this a number of other lenses manufacturers make lenses for these two camera manufacturers, for example Zeiss makes lenses for both Canon and Nikon cameras.
Criteria Eight: Learning Resources and Repair
Buy a camera others have, check the warranty and avoided the gray market:
What also follows from their dominance in the market is there are far more free learning resources on the internet for Nikon and Canon than any other manufacturers. Also camera store employees are more familiar with these cameras as well.
Another considerations is buying a camera your photography friends have. If you go out shooting with a group of people who are mostly Nikon based then you are likely go get more help, tips and new ideas about how to use your camera than if you have a camera they do not own.
Finally digital cameras need attention to keep them operating properly you may find about every year or year and a half you need to make a trip to the repair depot. So do a little research and find out how far away it is and what the service standard is for turnaround time on basic maintenance.
You should also look into both the length of warranties and what it includes as well as extended warranties. As with everything they are not all equal. Make sure you purchase the camera in the country you live in, a camera purchased in the US will not be warranted or services in another country. You will likely have to ship it back to the country of origin to get warranty service or pay for the service out of you own pocket.
Finally if the camera you are attempting to purchase has a price to good to be true then it is most likely a gray market camera. These are a world of woe and not worth the potential saving.