Archive | December, 2013

Winner of the RAW buffer race

19 Dec

Due to my ongoing interest in RAW buffers and how they affect camera performance, I recently took-a-look at some flagship models that had been touted as having particularly fine performance in this area – meaning, they can take many RAW images in quick succession without slowing down your shooting.

The dilemma with RAW buffers is that they’re always too small. What’s more, as the buffer fills, the additional time the camera will have to remain on in order to “finish up business” (i.e. process and write to card the buffer contents for persistent storage) increases, which may disconcert some users. It’s not unusual for current higher-specced camera models to have a buffer that takes half a minute to just under a minute to “clear”. Cameras that process and write faster can be switched off sooner, and continue to operate at an acceptable and responsive rate even when the buffer is full. Hence, both buffer depth and write speed play a significant role in

I’ll venture to say that in order to be a respectable semi-pro camera (I’ll define that as the segment inhabited by the K-5 and successors, D7x00 and 7D/70D) or above, you need to have at least 3 seconds of RAW+JPEG buffer at maximum continuous drive speed (marked C-HI on Nikon cameras that have a dedicated dial for this selection). Critics were quick to point out the D7100 had only 0.8 seconds in spite of only a mid-field frame rate of 6fps (the new Pentax K-3 has 8.3fps). But is that criticism justified? Here, I take a look across APS-C flagship models of the three brands that are still focused on producing DSLR workhorses.

What nobody mentioned in the D7100 debate was that its entire buffer clears within two seconds – at 2.5fps. This means that where other cameras drop to 1fps once the buffer fills, the D7100 can continue shooting at a theoretical 2.5fps maximum rate even with its buffer full. In reality, of course, the results aren’t quite as stellar, but it’s clear that it should still outperform the K-5 (approx. 0.7fps after buffer full), K-30 (NB 1.5fps after buffer full) and of course its predecessor, the D7000 (1.1fps).

However, there is an unexpected champion in this race, and that’s the two-year-old Canon EOS 7D, which not only accommodates 22 RAW+JPEG images in its buffer, accounting, at its 7fps frame rate for 2.75 seconds of shooting, but also thereafter clears the buffer quickly enough to continue shooting at 2fps. Therefore once you get good at shooting short bursts at relevant moments, the 7D may leave you virtually unencumbered. It’ll be interesting to see if its overdue replacement will continue its virtues.

In conclusion, the Nikon D7100 will serve the continuous shooter much better than its reputation would suggest, but if you’re looking for the ultimate in buffer performance in a current APS-C flagship, you can’t do better than the Canon 7D.

Frame rates cited as published by manufacturers. All other figures in this article were cited from, or calculated based on, measurements published at imaging-resource.com (IR). The Pentax K-3 could not be included as IR had not yet published test data for it.

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Why high resolution cameras don’t need an AA filter

17 Dec

Disclaimer: Unfiltered truth ahead.

Digital cameras used to have a problem, which was that their lenses were so sharp that images would show moire or aliasing if there wasn’t an additional anti-aliasing or low-pass filter placed directly in front of the sensor to add a small amount of blur. Side effects of this filter include a small reduction in light transmission and a slight distortion of the colour distribution.

As camera sensors got to around 16MP APS-C or around 40 MP full frame, it became apparent this problem wasn’t so much of a problem any more. Glass quality generally wasn’t good enough to still cause moire and other aliasing at this tight packing of Bayer array and photosites. The lenses themselves served as AA filters, and throwing in an low pass filter on the sensor only made images blurrier, without any particular benefit. So some smart executive or engineer at Nikon said, “let’s ditch the thing and see if our customers like it”. And the customers came, and they saw that it was good, and they bought it.

Around the same time, some Pentax execs likewise came together and said unto each other, “let there be unwavering sharpness”. But knowing full wele that the Nikon gods had spread their bets across two models, one with and one withoute AA filter, the good sirs of Pentax did likewyse, and thus there came to be the K-5 II and IIs, made in the D800E’s image.

So there you have it: the story of why you can buy a D800E or K-5 IIs without regret. And how, as an engineer, you can do something for very good reasons and completely fail to communicate this to the customers. Probably because upper management told you to keep your trap shut about the sharpness of the lenses. And the fact that the Ricoh GR and Fujifilm X100S take sharper pics than your monster-tea-bagging SLR.

So there you have it: the reason you can leave that K-3 AA simulation switched off, save battery power, and never worry. Woohoo!