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| p.3 #4 · p.3 #4 · New Zeiss article on the design of wide angle lenses |
Hi. In the past, you've mentioned that Leica really isn't using an exceptionally thin IR filter on the M9. Do you know what Leica is doing to preserve sharpness at the edges? Does it mostly come down to the lack of an AA filter? Thanks.
Yes, the impact on both CA and astigmatism is down to the TOTAL thickness of the filter package, and the AA-filter is a rather large part of this. How the separation of the filter into two separate stacks (one on the sensor surface and one outer layer coupled to a "dust-off" vibrator) that most cameras use impact this I actually haven't given much thought. It might lower CA and increase astigmatism.
My complaints about the usual Leica corporate sales hype was that an "extra thin IR filter" is definitely NOT the reason why their filterstack is pretty thin, quite the other way around. They use a sub-par quality IR material, the least effective (and cheapest...) material of any manufacturer that I know of. Other manufacturers use thinner, more expensive filters, with better filtering properties. How does this translate into Leica saying: -"We use new, thinner IR filters"? Well, compared to their older, even cheaper constructions it may be true - but not in a general sense they use the words.
It's kind of like the new camera in the iPhone 4, where they use the "revolutionary new hybrid IR filters" to improve quality. *Cough*. Most other (even low-end) manufacturer has been doing this since 2004. Most camera manufacturers have been doing this since the Nikon D100. This "revolutionary" type of hot-mirror / absorbent filter has been used in similar filterstacks in various scientific applications since the early 70's
It's all about the high-strung wording, and having an intended audience that will bend over and believe any blurb the [favourite brand] publishes.