Re: Special lenses for digital
A while ago one of our number experienced a ghost image in one of his *istD shots, and asked what it might be. It looked like a classic type of ghost image that has been known since the beginning of photography, but some folks here were adamant that it was caused by reflection from the sensor. Of course it was possible that it WAS from the sensor, but why look for a more complex explanation when a simpler explanation - that the ghost image came entirely from the lens or filter - already had a history as the source of ghosting flare. The photographer in question soon proved that an uncoated filter was the cause of the problem by reproducing the ghost images deliberately, and then noting the absence of ghost-imaging when the filter was removed. The 'It's The Sensor's Fault' chorus fell suddenly silent. My feeling is that 'Digital Problems' are more likely to be some of the less common occurences of camera-work that are being experienced due to the sheer volume of shots being taken by new digital photographers. The laws of probability are simply catching up on them. Admittedly, a shiny sensor can be the source of ghost images or scattering flare, but those problems can only follow through to completion if the stray light encounters substandard baffling in the mirror-box, or substandard coating on optical surfaces. We Pentax users have long been well served on the last point, but it seems that time and progress has caught up on some Other Brands who have been content to apply the lens coatings of their accountants' choice. regards, Anthony Farr - Original Message - From: "John Forbes" <[EMAIL PROTECTED]> > Have any digital slr users experienced the sensor-reflection phenomenon > referred to by Keppler? > > It's a bit worrying. I have been buying up lots of cheap (but good) old > Pentax lenses on Ebay in anticipation of buying a *ist D. > (snip)
Re: special lenses for digital
Hi, [EMAIL PROTECTED] wrote: > > It's not the sensor (film reflects light too--hence TTL flash) but the > glass anti-aliasing filter in front of it. It too should be designed to > transmit light but glass is never perfect--that's what SMC is all about. So does the filter have SMC (Ghostless?) coating? We should be told! mike
Re: special lenses for digital
Thank you for that reassurance. John On Tue, 24 Feb 2004 11:58:50 -0600 (CST), <[EMAIL PROTECTED]> wrote: Date: Tue, 24 Feb 2004 11:36:07 - From: John Forbes <[EMAIL PROTECTED]> Have any digital slr users experienced the sensor-reflection phenomenon referred to by Keppler? Not that I'd know. Perhaps I would get 5% better performance if this phenomenon were eliminated but I'd never notice. It's a bit worrying. I have been buying up lots of cheap (but good) old Pentax lenses on Ebay in anticipation of buying a *ist D. Stop worrying! I've shot screw-mount takumar lenses on the *istD and they look great. My girlfriend's A and M lenses are quite sharp and contrasty with her *istD. If you absolutely have to have UNCOMPROMISED performance buy a Leica or a Hasselblad and shoot Fuji velvia all the time. I have never seen a real sensor up close, but I wouldn't have expected them to be too reflective. After all, they're meant to read the light, not reject it. It's not the sensor (film reflects light too--hence TTL flash) but the glass anti-aliasing filter in front of it. It too should be designed to transmit light but glass is never perfect--that's what SMC is all about. It's one of those things that smack very much of hype in order to get consumers to buy new lenses, but at the same time it clearly could be true. Lots of things can be done to optimize the performance of lenses for digital, so when designing such a DSLR lens it is prudent to do them. In the meantime, lots of pros are getting stunning results using older lenses on DSLRs and not complaining about the possible 5% contrast loss from sensor-reflectivity or the 5% illumination loss from the light not coming into the sensor just straight at the edges. DJE -- Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/
Re: Special lenses for digital
On 24 Feb 2004 at 11:36, John Forbes wrote: > Have any digital slr users experienced the sensor-reflection phenomenon > referred to by Keppler? > It's one of those things that smack very much of hype in order to get > consumers to buy new lenses, but at the same time it clearly could be true. Hmmm, you may be right, I've not seen any problems however SMC is pretty good has been sued on all elements for many years. I can't see why such problems wouldn't have been visible when using slide films although any reflections may have been sufficiently diffused by the film emulsion as to make them less apparent. Keppler is usually believable but I'd still like to see some examples of this phenomenon. The only references to the problem that I can find seem to be at astro sites. Rob Studdert HURSTVILLE AUSTRALIA Tel +61-2-9554-4110 UTC(GMT) +10 Hours [EMAIL PROTECTED] http://members.ozemail.com.au/~distudio/publications/ Pentax user since 1986, PDMLer since 1998
