The real story behind APS-C versus Four Thirds versus Full Frame sensors

With digital cameras, many enthusiasts engage in “pixel peeping” contests to super enlarge and examine every image pixel for bragging rights over whose image is sharper or has less digital noise.

This leads to pointless debates over the effectiveness of different types of camera sensors that usually leave out so many details as to be, well pointless debates.

If you’d like to know more about sensors and other aspects of photography, read what a physicist writes on his personal blog:

When I hear people claiming that the Four Thirds format is incapable of providing resolutions above 10 MP, I just laugh. Then, hearing the same “experts” say that APS-C sensors can deliver such resolutions, just because they are bigger, I don’t know whether to laugh or to cry. Stop worrying about pixels, start thinking about lenses. Or just start thinking.

via wrotniak.net: Four Thirds Sensor Size and Aspect Ratio.

His conclusion is similar to mine, outlined in my last sentence here.

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43 Rumors – Olympus financial results not so merry

43 Rumors | Home. Questions arise about the financial results for Olympus. Thom Hogan, in a comment, notes that Olympus itself is fine – but the imaging division isn’t fine. And then there is Kodak … whose share price has fallen to $3.

Lacking consistent credible progress towards addressing their challenges, both companies have some huge issues to address to remain in their respective businesses. Who knows? I do not predict the future!

Interested in attending the NAB Show?

NABshow Las Vegas, NV; NAB 2008

The 2011 National Association of Broadcasters convention (or just “NAB Show”) will be held April 9-14 in Las Vegas. The entire world of broadcasting, radio, television, film production, media, related software, transmitters, lighting, sound, cameras, DSLRs, video, online media production – you name – will be in Las Vegas.

NAB is huge. Mind blowingly huge.

You can receive a free, complimentary registration as follows:

We have a special registration code you can pass along to your readers, giving them FREE ACCESS to the exhibit floor, the Opening Keynote and State of the Industry Address, Info Sessions, Content Theater, Exhibits and PITS – a $150 value. Please pass this along and visit http://bit.ly/NABRegSM06 to redeem or register at http://nabshow.com/register with the code SM06.

More information on the NAB Show at http://blog.nabshow.com

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Why Canon DSLRs may have “soft” 1080p video

Front View of the Canon EOS-1D Mark III Digita...
Image via Wikipedia

There are many reviews online that say the Canon DLSRs, which are fantastic still cameras, are lacking in their video mode 1920x1080p resolution.  Several web sites calim that the Canon DSLRs (not including the 5D) in 1080p mode are only a little better than 720p when tested on resolution charts.  Online video examples show that the 1080p resolution is not the 1080p resolution of a true video camera.

And then there are the video resolution charts.

Why might this be going on?

How do they down sample a 5184 x 2192 (16:9) raw image (using the 60d specification here – the 5D has slightly larger numbers)?

Here is my technical explanation for a possible reason, if the online reviews are correct about the soft video images. (I do not own a Canon DSLR so cannot test this myself.) My explanation may very well be off in space but provides a plausible technical reason. But I can’t say this enough: my explanation may totally wrong! And keep in mind that most people do not even see a difference between 1080p and 720p video on their home HDTV. (And my explanation is wrong in the details – each “photo site” has 2 green, 1 blue and 1 red image sensor. Translating this into megapixel images is more complex than in my simplified explanation.)

The image sensor on the camera is much higher resolution than 1920×1080 used in video. The original image must be converted or downsized to 1920×1080.

They likely take every 2nd row and every 4th pixel across and throw away the extra rows and pixels. In 16:9 aspect ratio, the camera (60D) has a resolution of 5184 x 2192.

If this raster is simplified by pulling out every 4 pixel and every other row, this yields, for 1080p:
5184/4 = 2592 pixels wide (or alternatively, take every 2 of 3 for 1,728)
2192/2 = 1096 rows high

To convert this into 1920x1080p, they might do a simple weighted average of pixels horizontally across each row (the 2592 wide row or up size the 1728) to produce a 1920 row. This is going to soften the image horizontally but is an easy way to get to 1920. Dropping out rows, too, loses information and other processing adds information that wasn’t there (by averaging multiple elements) creating moire and aliasing. The result is an image that looks better than 720p but softer than true 1080p.

(There’s a reference in a comment here that the 5D samples every 3rd row and another comment saying it throws every 3rd row … take your pick!).

720p is much simpler:
5184/4 = 1296
2192/4 = 728

which is so close to 1280×720 that all they need do is throw out some pixels at top and bottom. This creates worse moire because even more rows are thrown away.

The Canon 720p should look fine except for moire. The Canon 1080p is going to look softer than true 1920x1080p and introduces aliasing artifacts.

With only one DIGIC 4 processor on board, they likely lack the processing capacity to do a clean conversion from 5184×2192 sensor down to 1920×1080, 30 times per second! Instead they take shortcuts to make it work.

My prediction: Starting this fall, the Mark III has a dual core processor and all cameras announced from then on will have dual core processors. Within 1 year, Canon will solve the moire problem.

Some of the cameras from competitors have dual core or even tri-core processors now.

DSLRs do enable photographers to shoot very narrow depth of field video, which would be harder to achieve on all but high end professional video cameras that are very expensive – or by using various schemes, like the Letus adapter, that project the image on to a screen.

DSLRs also generally have very good low light performance capabilities.

Ultimately, resolution is hardly the only criteria for shooting with a DSLR. Convenience, size, low light, depth of field, lens quality and that you just like how the image looks anyway may be more important.

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Are video capable DSLRs really smaller and lighter “run and gun”?

Numerical Reflex Digital Camera
Image via Wikipedia

vDSLRs are not smaller & lighter, nor cheaper. « I E B A Tech Thoughts.

The picture at the link says it all 🙂

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