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04-08-2016, 11:25 AM - 1 Like   #76
osv
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QuoteOriginally posted by rfkiii Quote
It is quite possible for a lens to be sharp across the frame wide open, even at f1.4. The Zeiss Otus series proves this and is famous for this. I was first introduced to wide open "landscape shooting" relatively recently (where "landscape shooting" presumes not only good sharpness from front to back but good sharpness across the frame into the corners and edges, the latter being a function of how well lens aberrations are handled by the designers) with the Canon 24-70 II which can be used at 24mm/ f2.8 (wide open) and produces acceptably sharp corners/edges. This lens was a huge eye-opener. If one's composition is at infinity distance across the frame (nature's flat wall), no DoF essentially, then such lenses can render such compositions sharp (in focus) across the frame. When objects are placed closer than infinity to the shooting position, then DoF comes into play and one must stop down to render this object "in focus". Obviously, how much one has to stop down is determined by how close that object(s) are placed to the shooting position (assuming one wants good front to back sharpness). What one does not want to do, if possible, is to stop down just to fix lens aberrations as in the case of compositions featuring infinity across the frame. Nothing about lens design demands that a lens' "sharpness" (in focus) must drop off in the corners at wider or wide open pertures other than meeting a price point and/or customer satisfaction.
finally, someone gets it.

however, given that i already posted an f/2 example photo that had practically no field curvature characteristic, other than defects, it really shouldn't have been such a difficult concept for other people to understand

QuoteOriginally posted by rfkiii Quote
Amazingly, I have stopped down to f32 on the 645z without the visible softening associated with f16 on a FF system (impressionistic not scientifically derived)..
that's because, in part, the lower pixel density of the 645z makes diffraction less visible, but afaik, it doesn't change the amount of diffraction there is... now ask yourself what it'll look like with a 100mp mf camera.

---------- Post added 04-08-16 at 11:30 AM ----------

QuoteOriginally posted by rfkiii Quote
I wasn't suggesting a direct causal effect but there is an indirect effect. Stopping down has pros and cons. The pro for landscape being that stopping down brings objects into focus (including edges and corners rendered out of focus by lens aberrations) but stopping down can also bring on diffraction. If one's composition has no close objects and the only reason to stop down is to fix out of focus corners and edges, then a better designed (and more expensive ) lens would eliminate this need and as an extra benefit, avoid possible diffraction issues.
that's it exactly.

---------- Post added 04-08-16 at 11:41 AM ----------

QuoteOriginally posted by 2351HD Quote
There is a big difference as to what a DOF calculator says will be acceptably sharp and what actually "IS" acceptably sharp in the real world. These calculators are well off in my experience.
i agree, yes they are off, the entire concept of dof is based on what is an acceptable amount of visual blur near the area of critical focus.

but the general differences will be accurate, be it two feet or three feet in the 28mm example... if someone is blindly stopping down to f/11, for no reason, it's a waste of expensive camera gear.


Last edited by osv; 04-08-2016 at 11:31 AM.
04-08-2016, 12:50 PM   #77
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QuoteOriginally posted by Rondec Quote
Changing number of megapixels could help when printing bigger, but I don't know that it really changes anything else. Personally, I want better pixels, not more of them, but each to his or her own.

Increasing the number of pixels on the same size sensor always increases the resolution of detail captured all other things being equal. Folks who have the 645D and 645Z could demonstrate this principle of digital imaging quite easily. By "quite easily", I mean the methodology of producing a comparison. The difference in resolved detail may not be as dramatic as one might think from reading these threads, some posts more hyperbolic than others, but it will be there nonetheless especially at pixel peeping levels. What could outweigh any gross advantage of higher capture resolution in the aforementioned example of the 645D vs. the 645z among other things would be the rendering of the different sensors which I have read are visibly different.


To quantify resolution across the same size sensor or different sizes of sensors, look for the pixel density or the pixel size.


"Pixel Density is a calculation of the number of pixels on a sensor, divided by the imaging area of that sensor. It can be used to understand how closely packed a sensor is and helps when comparing two cameras with different sensor sizes or numbers of photosites (pixels). Because the light collecting area and efficiency of each photosite will vary between technologies and manufacturers, pixel density should not be used as a predictor for image quality but instead as a parameter to help understand the sensor. "
04-08-2016, 03:53 PM   #78
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QuoteOriginally posted by rfkiii Quote
Increasing the number of pixels on the same size sensor always increases the resolution of detail captured all other things being equal. Folks who have the 645D and 645Z could demonstrate this principle of digital imaging quite easily. By "quite easily", I mean the methodology of producing a comparison. The difference in resolved detail may not be as dramatic as one might think from reading these threads, some posts more hyperbolic than others, but it will be there nonetheless especially at pixel peeping levels. What could outweigh any gross advantage of higher capture resolution in the aforementioned example of the 645D vs. the 645z among other things would be the rendering of the different sensors which I have read are visibly different.


To quantify resolution across the same size sensor or different sizes of sensors, look for the pixel density or the pixel size.


"Pixel Density is a calculation of the number of pixels on a sensor, divided by the imaging area of that sensor. It can be used to understand how closely packed a sensor is and helps when comparing two cameras with different sensor sizes or numbers of photosites (pixels). Because the light collecting area and efficiency of each photosite will vary between technologies and manufacturers, pixel density should not be used as a predictor for image quality but instead as a parameter to help understand the sensor. "
I think the 645Z has "better" pixels than the 645D (more dynamic range, more color depth), just like on a smaller level, the K5 had better pixels than the K7, even though absolute number of pixels was similar. On the other hand, the K3 has more pixels, but less dynamic range at base iso. This is the sort of trade off that is more difficult to take. My feeling is that there must be a sweet spot and if you drop pixel size below a certain amount, your photon wells shrink and your dynamic range will begin to drop.

But since I don't know much about the science behind it, I guess I should leave it to others to comment.
04-08-2016, 04:11 PM - 2 Likes   #79
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I'm plane too busy to focus on this thread, but I DOF my cap to the energy levels on show. On white balance I couldn't give a diffraction about most of it though.

04-09-2016, 06:20 AM   #80
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QuoteOriginally posted by unkipunki Quote
I'm plane too busy to focus on this thread, but I DOF my cap to the energy levels on show. On white balance I couldn't give a diffraction about most of it though.
Perfectly stated for me, including the cringe inducing puns rhetorical twists.
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