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What is the gold standard for sharpness?
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PostPosted: Sun Mar 27, 2011 12:44 am    Post subject: Reply with quote
thePiRaTE!! wrote:






@thePiRaTE!! - Wow, that's a sharp lens AND camera Shocked

I would agree that most Zeiss lenses are super sharp. My 50/1.4 and 28/2.8 in C/Y mount are scary sharp...oddly, I rarely use them... Wink


PostPosted: Sun Mar 27, 2011 5:46 am    Post subject: Reply with quote
mmm.... tacky sharp Smile .
thePiRaTE!! wrote:
GOLD STANDARD LENS... and camera (photo from PentaxLife)



[/end]


K.


PostPosted: Sun Mar 27, 2011 12:38 pm    Post subject: Reply with quote
enzodm wrote:
mmm.... tacky sharp Smile .



Very Happy


PostPosted: Sun Mar 27, 2011 3:55 pm    Post subject: Reply with quote
enzodm wrote:
mmm.... tacky sharp Smile .
thePiRaTE!! wrote:
GOLD STANDARD LENS... and camera (photo from PentaxLife)



[/end]


K.


Welcome to the forum enzodm!


PostPosted: Sun Mar 27, 2011 5:08 pm    Post subject: Reply with quote
enzodm wrote:
mmm.... tacky sharp Smile .
thePiRaTE!! wrote:
GOLD STANDARD LENS... and camera (photo from PentaxLife)
...

K.


hahaha, now thats funny!

K.


PostPosted: Mon Mar 28, 2011 3:26 am    Post subject: Reply with quote
I suppose the ultimate in sharpness would be diffraction-limited performance across the entire sensor from corner to corner, at all apertures, and at all supported distances, at all supported wavelengths.

I doubt any camera lens can do this, but some small APO triplet refractors (80-100mm, f/6- f/8 telescopes) come close to perfection at infinity focus at the very center of the field. Unfortunately, the field for imaging is not flat across the sensor on these telecopes, and adding a field flattener can cause problems (like CA).

I suppose a lens is good enough for photography, if the spot diameter (like a star image on the sensor) is smaller than a pixel at all points on the sensor. BTW, I haven't (yet) seen any lenses like this at f/2.8, although some lenses are really good at the center of the field. I'll keep looking, though.


PostPosted: Mon Mar 28, 2011 5:42 am    Post subject: Reply with quote
Most 50mm lenses are very sharp at f8.

Last edited by jjphoto on Sat Mar 16, 2013 1:11 pm; edited 1 time in total


PostPosted: Mon Mar 28, 2011 6:57 am    Post subject: Reply with quote
s58y wrote:
I suppose a lens is good enough for photography, if the spot diameter (like a star image on the sensor) is smaller than a pixel at all points on the sensor. BTW, I haven't (yet) seen any lenses like this at f/2.8, although some lenses are really good at the center of the field. I'll keep looking, though.
We all just need 6x6cm 6MP sensors and we can get marvelous pictures with more or less crappy lenses.


PostPosted: Mon Mar 28, 2011 11:36 am    Post subject: Reply with quote
Quote:
We all just need 6x6cm 6MP sensors and we can get marvelous pictures with more or less crappy lenses.


In this case, a bad lens with a spot diameter of 25 microns (if I did my computations correctly) wouldn't be much worse than the best lens, given the sensor limitations. Of course, this would only be for astroimaging, where things like bokeh, "3D rendering", image drawing", and "character" don't matter.


PostPosted: Mon Mar 28, 2011 11:45 am    Post subject: Reply with quote
s58y wrote:
Of course, this would only be for astroimaging, where things like bokeh, "3D rendering", image drawing", and "character" don't matter.
Do you mind elaborating why that would be the case? I'm a bit confused, as my 6MP Nikon D40 always rendered nice photographs.


PostPosted: Mon Mar 28, 2011 12:24 pm    Post subject: Reply with quote
Quote:
Do you mind elaborating why that would be the case?


I can really speak only for astroimaging, where sharpness at all wavelengths and good lens speed outweight everything else. For daylight photos, someone already posted that "character" is more important than sharpness. A lens with a spot diameter less than the pixel size might not be enough (or even required) for good daylight photos.

In astroimaging, we usually don't want character in the optics, since the sensors already have more than enough character to cause problems with long exposures of dim objects.


PostPosted: Mon Mar 28, 2011 1:04 pm    Post subject: Reply with quote
Cistron wrote:
s58y wrote:
Of course, this would only be for astroimaging, where things like bokeh, "3D rendering", image drawing", and "character" don't matter.
Do you mind elaborating why that would be the case? I'm a bit confused, as my 6MP Nikon D40 always rendered nice photographs.

But your D40 didn't have a 6x6cm sensor. It's about the relationship between pixel size and the circle of confusion (or spot diameter as s58y calls it). Any regular lens will have a high enough resolution to keep the circle of confusion smaller than the huge pixel size of a 6x6cm 6MP sensor (for anything within the DOF).

If you didn't understand the part that you quoted: bokeh isn't applicable to astro imaging because the entire subject will always be in focus (as long as there is no field curvature). I'd imagine that things like microcontrast and colour balance (due to coatings) still play a role for refractors.


PostPosted: Mon Mar 28, 2011 1:27 pm    Post subject: Reply with quote
AhamB wrote:
But your D40 didn't have a 6x6cm sensor. It's about the relationship between pixel size and the circle of confusion (or spot diameter as s58y calls it). Any regular lens will have a high enough resolution to keep the circle of confusion smaller than the huge pixel size of a 6x6cm 6MP sensor (for anything within the DOF).

If you didn't understand the part that you quoted: bokeh isn't applicable to astro imaging because the entire subject will always be in focus (as long as there is no field curvature). I'd imagine that things like microcontrast and colour balance (due to coatings) still play a role for refractors.
I understand that 6x6 will be medium format with all its properties. I don't understand how a crisp image caused by pixel>CoD influences Bokeh. Is it because the transitions will be quite abrupt?

PS. This are just my ruminations as a boffin. No-one will ever make a 6MP medium format, alas.
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