All Forum Comments
Comment by MostlyHarmless posted on 645D lost the competition at 11/03/2010 - 12:31
Mongoose wrote:
According to the spec sheet for the Kodak sensor which matches the specs of the 645D most closely (we don't know if that's the actual sensor to be used, but the specs will be similar) it has a saturation charge of ~41 thousand electrons.
Since you can't have part of an electron, there are 41000 possible levels of output from that sensor. 2^14 is ~16000 levels while 2^16 is ~65000 levels. So assuming that sensor (which may or may not be the one in use in either camera), 16bit should be better than 14 although not quite as much as might first appear.
...
So in short, yes, you're right, we're too close to quantum physics to pretend that true analogue signals exist in nature at this point, but the step up from 14 to 16 bit does appear to be justifiable from the sensor specifications.
I understand what you're saying but don't you have to take the read noise into account? I'd found MostlyHarmless wrote:
Neal
...Mongoose wrote:
the sensor is analogue, it produces a voltage signal which is measured by the A/D converter. The sensor itself doesn't have a "native" bit level.
Sorry, I wasn't clear. ...the sensor is analogue, it produces a voltage signal which is measured by the A/D converter. The sensor itself doesn't have a "native" bit level.
Neal
According to the spec sheet for the Kodak sensor which matches the specs of the 645D most closely (we don't know if that's the actual sensor to be used, but the specs will be similar) it has a saturation charge of ~41 thousand electrons.
Since you can't have part of an electron, there are 41000 possible levels of output from that sensor. 2^14 is ~16000 levels while 2^16 is ~65000 levels. So assuming that sensor (which may or may not be the one in use in either camera), 16bit should be better than 14 although not quite as much as might first appear.
...
So in short, yes, you're right, we're too close to quantum physics to pretend that true analogue signals exist in nature at this point, but the step up from 14 to 16 bit does appear to be justifiable from the sensor specifications.
this sensor, which quotes 42Ke at saturation - but also 13e read noise which (assuming my understanding of read noise is correct - effectively the error bar on how accurately you can read the no. of electrons in each well) means 14 is more than enough? In fact isn't 12 enough?
Comment by MostlyHarmless posted on 645D lost the competition at 11/03/2010 - 00:19
Mongoose wrote:
the sensor is analogue, it produces a voltage signal which is measured by the A/D converter. The sensor itself doesn't have a "native" bit level.
Sorry, I wasn't clear. As I understand it, attempting to digitise the sensor output with 'too many' bits doesn't get you any more 'real' image data, just better digitised noise which isn't particularly helpful. I don't exactly know what 'too many' is in this context, but I believe it's < 14, so 14 vs 16 (vs 22) is moot except for marketing.the sensor is analogue, it produces a voltage signal which is measured by the A/D converter. The sensor itself doesn't have a "native" bit level.
Neal
Comment by MostlyHarmless posted on 645D lost the competition at 10/03/2010 - 15:17
Anvh wrote:
The K10D use a whopping 22-bit A/D converter for example so it must be good
And the 16 vs 14 bit argument is about the A/D converter (as I understand) - so since 14 bits is already more than you get out of the sensor, 16 bit is basically just digitising the noise in a bit more detail?The K10D use a whopping 22-bit A/D converter for example so it must be good
Neal
Comment by MostlyHarmless posted on 645D lost the competition at 10/03/2010 - 13:53
As you stop down you'd expect to see a disproportionate increase in performance from a 'lower-performing' lens, and by f11 you're approaching diffraction issues for APS-C sized sensors which is going to further handicap a 'higher-performing' lens. So by f11 you're going to be pushed to observe clear differences between an 18-55, a 16-45, a 17-50, a 17-70 or a 16-50 (probably). If I was living around f8-f16 all/most of the time, I think I'd have stuck with the 18-55 provided 18 was wide enough. Galen Rowell (I think?) was famous for using cheap and light consumer grade lenses and stopping them down.
Neal
Neal
Comment by MostlyHarmless posted on 16-45mm £229 or Tamron 17-50mm?? at 08/03/2010 - 10:12
WobblyGoblin wrote:
Failed to convice my Dad to purchase a KX...
He has decided to spend his birthday money on a Nikon [...]
Exactly the opposite of what happened to me (best part of 20 years ago mind) - I had a Nikon FE2 and he got a Pentax despite my "we'll be able to share lenses" pitch - worked out in the end thoughFailed to convice my Dad to purchase a KX...
He has decided to spend his birthday money on a Nikon [...]
Neal
Comment by MostlyHarmless posted on There was nothing I could do! He just wouldn't listen... at 05/03/2010 - 21:40
thoughton wrote:
Stefan I can't remember much about the details, but I'm sure there was a Nikkor 58mm f1, and a Nikkor 85mm f1.
Also don't forget Stanley Kubrick's Zeiss 50mm f/0.7 lens.
There was certainly a Nikkor 85mm f1 (and a 75mm one too 5 think) but I'm 90% sure they're not F-mount - '53mm mount' and the adaptor next to it in the picture are a clue - so no need to be retrofocus designs?Stefan I can't remember much about the details, but I'm sure there was a Nikkor 58mm f1, and a Nikkor 85mm f1.
Also don't forget Stanley Kubrick's Zeiss 50mm f/0.7 lens.
Kubrick's f0.7 was used on a 'non-reflexed' camera, so presumably did not have any mirror/retrofocus issues either (pictures of Mitchell BNC cameras show a separate finder). I seem to remember from Nikon MF days that some lenses (fisheyes I think though - like this) would only work with the mirror locked up, and a supplementary finder - so once again the need not be retrofocus.
Neal
Comment by MostlyHarmless posted on Pentax K-5? at 04/03/2010 - 18:13
Turns out it came with a hood And a bag which was another bonus - I swear the description only said caps and box.
So all a bit academic really, but many thanks for the comments. I had thought about about the multi-stage rubber hoods and I've got a couple for other lenses. But I just don't get on with them any more. I used to like rubber hoods when all I had was (cheap and nasty) primes. I think it's the having to adjust them with zooms - granted that's the point and makes them more effective - I suppose it's just sheer laziness.
I really like the metal Heliopan ones - but they're not cheap and in any case they don't seem to do one in 72mm, and if they did even the short version would probably be too long in this case. If I still needed one. Which I don't...
Thanks
Neal
So all a bit academic really, but many thanks for the comments. I had thought about about the multi-stage rubber hoods and I've got a couple for other lenses. But I just don't get on with them any more. I used to like rubber hoods when all I had was (cheap and nasty) primes. I think it's the having to adjust them with zooms - granted that's the point and makes them more effective - I suppose it's just sheer laziness.
I really like the metal Heliopan ones - but they're not cheap and in any case they don't seem to do one in 72mm, and if they did even the short version would probably be too long in this case. If I still needed one. Which I don't...
Thanks
Neal
Comment by MostlyHarmless posted on Generic Petal Lens Hoods at 24/02/2010 - 22:26
Dear All, I've got a used Tamron 24-135 coming as a cheapish solution to a trip where I won't be able to take much - and it hasn't got a hood. I wondered if anybody had any experience with these
these? (you can get them on eBay too).
It can probably be modded easily if it vignettes at all - using the profiles on lenshoods.net - and not being reversible for storage isn't a problem for me. But (a) any idea if you can fit a lens cap with the hood attached (looks like a maybe to me from the pictures) and (b) are they just cheap and nasty tat?
Regards and thanks,
Neal
these? (you can get them on eBay too).
It can probably be modded easily if it vignettes at all - using the profiles on lenshoods.net - and not being reversible for storage isn't a problem for me. But (a) any idea if you can fit a lens cap with the hood attached (looks like a maybe to me from the pictures) and (b) are they just cheap and nasty tat?
Regards and thanks,
Neal
Comment by MostlyHarmless posted on Generic Petal Lens Hoods at 24/02/2010 - 10:09
The astrophotographers don't move anything - same temperature, everything. So yes it would affect the noise - but they are chasing minute amounts of signal in lots of noise, so I think I'd try taking it inside and seeing if I was happy with the results.
Neal
Neal
Comment by MostlyHarmless posted on K-7 long exposure bug? at 05/02/2010 - 13:58
... feel free to disagree....
Neal