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Digital Camera Sensor Size

November 18th, 2007


I wish camera manufactures would work on bigger sensors instead of more pixels. Old school photographers who swear by film cameras do have a point, but it’s not that film is better. The look and resolution of the film can be reproduced by digital techniques. Sensors are able to outperform film in almost every aspect. It’s the look of a medium format or large format film size and lens combination that can’t be reproduced. It’s all about the size relationship between the film and the lens. Longer focal length lenses are inherently sharper, and have shallower depth of field. They are also easier to precisely focus. When you combine these factors with the right of view, you have the big camera look. A wide angle lens on an 11X14 camera is a 210mm. A 210MM lens on a compact camera sized sensor will make the creators on the moon look like they are two feet from you. A wide angle lens on a compact camera is a 6MM. There’s nothing in digital that gives you the look of a “210mm wide angle lens.”

The diagram is sized down to fit on this blog, but the size relationships are still good.

The angle of view changes, but the other characteristics of the lenses stay the same. A 7mm lens has an incredible amount of depth of field at 2.8 mm. It also has a fair amount of distortion. It’s really tough to get shallow depth of field out of these small sensors. I often use Photoshop techniques produce shallow depth of field looks. The technique is simple.

  1. Duplicate the background
  2. Blur the new layer
  3. Add a black layer mask
  4. Paint the layer mask white where you want it sharp

It’s time for the manufacturers to stop cramming more pixels onto tiny chips and start making physically bigger chip and lens combinations. The signal to noise ratio will vastly improve if the chip dimensions grow and the chip resolution stays the same. More megapixels on a chip isn’t doing us much good at this point as we are at point were lens resolution is the lowest common denominator. At 15-17MP the lenses resolving power for the physical dimensions of the sensor becomes an issue. Raw processors like DXO can correct for lens some lens characteristics, but this is synthetic correction and doesn’t replace the need for true lens resolution.

Nikon finally has a full frame camera coming out in the Nikon D3. This is a step in the right direction for Nikon, but a fairly small step. The D3 retains the same 12 Megapixels, which is a decent size for many applications. The problem is that the Chip is cropped to 6Megapixels if you use the DX lenses. Nikon pushed DX lenses for their 1.5X multiplier sized chip and now those lenses will only get you 6 megapixel images. They do get fantastic high ISO results by not upping the pixel count.

The first compact camera to use a larger chip is the Sigma DP1. It uses an APS sized Fovion X3 sensor instead of the 4.73X multiplier sensors in most compact cameras. It also has a fixed 28MM sigma lens. This is a specialized combination, but could become a cult classic with photojournalist. I attended a presentation by 5 National Geographic photographers: Sam Abell, David Burnett, Annie Griffiths Belt, Bruce Dale, and Steve Uzzell. A seemingly silly question was asked: “What’s the best lens to use?” They all agreed that on a 35mm film camera a 50mm lens would be preferable because of the realistic representation. That would translate into a 28MM lens on a APS sized sensor. I was surprised that these great photographers all agreed so quickly. I expected the answer to be ” it depends on….”. I’m in advertising and I never try to make things look normal, but if 5 National Geographic photographers agree that a 50MM lens on a 35mm camera is going to produce good work, there must be something to it.

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