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Photography Archives

Canon Digital SLR Cameras and the Crop Factor

Digital cameras come with different size sensors. Compact cameras have tiny sensors – about the size of the nail on your little finger. On digital SLRs, the sensors are considerably larger, which is why these cameras produce higher quality images, particularly at ISO 400 or more.

Canon digital SLRs have three different sensor sizes, depending on the model:
1. Full-frame sensor, which is the same size as a 35mm neg (36 x 24mm), found on the Canon 1Ds and Canon 5D bodies.
2. APS-H sensor — slightly smaller than full-frame (28.7mm x 19.1mm); found only on Canon EOS 1D bodies.
3. APS-C sensor — smallest of the three (22.5 x 15mm); found on Canon Digital Rebels (400D, 450D, 500D), Canon 30D, 40D, 50D models, and the new Canon 7D.

Lenses made for traditional 35mm SLR cameras are designed so that the circular image cast by the lens just covers the rectangular area of the film (or a digital sensor of similar size).

When you substitute a full-size sensor with a smaller one, more of the subject now fills the frame — as in the picture below where the black rectangle represents a full-frame sensor, the blue rectangle an APS-H sensor, and the red rectangle an APS-C sensor.
Canon digital SLR crop factor

The impact of using a lens designed for full-frame sensors on a camera with a smaller sensor is commonly referred to as the “crop factor”, and also as “lens magnification factor” or “focal length conversion factor”.

The implications are enormously beneficial for photographers using long lenses on cameras like the Canon 50D or 500D, but simultaneously rob wide angle lenses of extra width. For more on this, please see my attempt at more fully explaining the Canon digital SLR crop factor, one of a new series of articles under Canon Lens Reports.

Energizer Photo Contest 2009 Finalists

Kobe the polar bear out for a swim at the Reid Park Zoo in Tucson, Arizona. Photo © Ruston Agte

Kobe the polar bear out for a swim at the Reid Park Zoo in Tucson, Arizona. Photo © Ruston Agte

Six category winners of the Energizer Ultimate Photo Contest have been announced and are now in the running for the main prize of a trip for two to the Galápagos Islands, plus the chance to have their photograph published in National Geographic magazine.

Following a public vote, the following were named Category Winners:
* Ruston Agte – Animals/Wildlife (right)
* Tracy Hagen – Nature
* Glenn Traver – Travel
* Frederick Abels – Weather
* Bernardo Medina – People and Cultures
* Bernardo Medina – Inspiration/Keep Going

You can view the winning photographs at on the Engergizer Photo Contest 2009 Finalists page.

My favorites is Frederick Abels’ Weather shot, although I also like both Bernado Medina’s pics, particularly his “Inspiration/Keep Going” entry – grit and head-down determination perfectly encapsulated.

Will Canon’s new EOS 7D Deliver?

After many rumors and much speculation, the new Canon EOS 7D digital SLR has been officially announced.


This is an entirely new camera as it doesn’t fit within any of the current ranges – the entry level Rebels (400D, 450D, 500D), the “prosumer” models (30D, 40D, 50D), or the pro range (5D, 1D, and 1Ds models). From all reports and available specs it’s apparently not a substitute for a 60D (assuming a 60D will at some stage replace the 50D in the prosumer lineup).

The 7D is not a full-frame digital SLR and comes with the smaller APS-C (22.3mm x 14.9mm) sensor as in the Rebels and prosumer models, giving a 1.6x crop factor and the ability to use both EF and EF-S lenses.

Stand-out features include eight FPS continuous shooting, 18-Megapixel Resolution and full HD video with variable frame rates and manual exposure control.

The EOS 7D has a completely new 19-point Autofocus system, a new Canon iFCL Metering System (Intelligent Focus, Color, Luminance) and 100% viewfinder coverage with a transparent LCD overlay that’s used to display/hide AF points and grid lines. The camera offers a range of ISO speed settings from 100-6400 (expandable to 12,800).

Although the camera sounds pretty impressive, for many the big question is whether it was necessary to cram 18 megapixels on an APS-C sensor, and the impact this will have on image quality.

Questions have been raised about the image quality of the 50D (15MP on a similar sized APS-C sensor), particularly at high ISOs where more noise reduction has to be applied to keep noise levels acceptable, meaning a loss of detail from ISO 1600 upwards.

In his review of the EOS 7D, Rob Galbraith says “Canon appears to have done a masterful job of wringing out every ounce of quality from the 7D’s little pixels (smaller than any Canon before), resulting in photos that are crisp, reasonably clean and eminently usable up to about ISO 1600.

“At ISO 3200 and beyond you’ll run into increasingly unmanageable amounts of digital dandruff (white pixels spread throughout darker areas) and plugged shadows.”

He adds: “Put in charge of the 7D’s development, however, we’d have chosen something like a 12MP sensor with better high ISO performance and richer low ISO files.”

This is so true, specially for photographers who shoot in low light and can’t use tripods – sports shooters, wildlife photographers, and press or wedding photographers who want to avoid flash.

Only a few years ago Getty Images would only accept digital images from the Canon EOS-1Ds with its 11.4 megapixels, so one has to ask whether 18 megapixels are really necessary. Will the 18MP of the 7D prove to be of more value to photographers than the ability to produce quality images at 3200 or even 6400 ISO? Time will tell.

The Canon EOS 7D Digital SLR camera will be available at the end of September, and will be sold as body-only at an estimated retail price of USD$1700.

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