Picture sharpness and air effects

[Andy Resnick]

<snip>If you really aren't concerned with quality then why not just use your 'phone - or your Wife's camera.

<snip>

Picture sharpness is only one of many compositional elements I consider. There are lots of times when I prefer to use my wife's camera- for example, when we are backpacking or traveling and I don't want to carry around mine, or if I am in a 'dirty' environment (dust/sand/salt air, etc) and I don't want to risk damage to my camera.

I got the sony because I wanted a color camera for the lab microscopes; 'scientific' color cameras (Jenoptik, Zeiss, Leica, etc) are horribly expensive and have very small image sizes. Recently, consumer electronic companies have come out with 35mm image format color cameras that are significantly less expensive, so I purchased a DSLR, a few adapters and a couple of lenses so that I could use the camera without the microscope.

Once I took a few photos with the 85mm I re-discovered photography (something I hadn't done since high school), now with the benefit of many years of experience using digital imaging systems. Applying quantitative imaging methodology to photography is easy (for me); learning how to use photography as an expressive tool is much harder (for me).

 

[sophiecentaur]

I really don't care about your photography habits. I never was. Neither do I want to upset you when I state only the truth about those pictures you posted. I was just concerned that your personal preference may have caused someone to avoid Raw when it might be of use to them. You are a bit of 'an authority' in these matters and people may take your personal preference as applying to their circumstances too. You would not want that to happen, I'm sure.
I might point out that this thread is,essentially, about picture sharpness at the 'high end', so I'm not sure that the performance of cameras which are carried for 'convenience' / ruggedness comes into this discussion.

Just please tell me (or clarify) what those b/w shots were taken on and whether you can be sure there is nothing 'going on' in the camera that may have produced those different graphs and the reasoning behind your statement about them. Was it a Lab camera (used for your Scientific Imaging) or a domestic digital camera? Can't we just discuss a bit of possibly useful technical evidence that you have submitted?
I may have failed to understand your explanation about that and I'd appreciate a constructive response. Do you understand the point I have made?

 

[Andy Resnick]

Just please tell me (or clarify) what those b/w shots were taken on and whether you can be sure there is nothing 'going on' in the camera that may have produced those different graphs and the reasoning behind your statement about them.

All images I post here, unless I say otherwise, are taken with the sony a850. Although I have a good understanding of the behaviors of the various lenses I use, I have no idea about what goes on inside the camera. And it's not relevant to me: single-chip color cameras are not appropriate for metrology.

 

[sophiecentaur]

SO, to help me a bit further, are there, in fact, any shots from other cameras and have you 'said otherwise' on this thread and have I missed it (apart from your Wife's sand shot)? If the b/w shots are from the sony, then do you still not want to comment on graphs and visibilities? What have you to risk?

I still don't know whether there is any actual 'metrology' on this thread. If there isn't then why are you bringing up what you do in your day job? If you choose to ignore the possibility of what goes on inside your sony having an effect then where is the Science in what you are writing?

 

[Andy Resnick]

I don't understand what you are asking (other than identifying cameras- and I have not posted any photos using my EMCCD or my digital video camera except in post 10 of this thread).

 

[sophiecentaur]

Thank you for that confimation. You made a statement about perceived sharpness being related to level. You showed two pictures and two graphs - to illustrate / justify the statement (?). I have asked many times how this evidence justifies your assertion.
Also I have made the point that in-camera processing involves 'sharpening'. You say that you kwow nothing of what your camera does in that respect. You say that one of those pictures looks sharper and I agree. The graph seems to show some edge enhancement. So how do your two pictures justify your statement?
Moreover, with such a big unknown in the signal chain, can one come to any serious conclusion about this?
With Jpeg processing included, the situation is even less certain.

 

[Andy Resnick]

You made a statement about perceived sharpness being related to level. <snip>.

If I did, that was not my intention. In terms of linear systems analysis, the perceived (meaning visual appearance) sharpness of an image is set by the contrast at midrange spatial frequencies. The cutoff frequency (the 'resolution limit') is less important to the visual appearance than the contrast at midrange spatial frequencies.

There is an excellent discussion of this (contrast sensitivity function) in "Basic Vision" (Snowden, Thompson, and Troscianko)

 

[sophiecentaur]

I think we are nearly there.
It was post 43. You say that the line scans show the image quality is the same. Do they? (This is what I have been questing all the time.) One has what looks like 'ringing' and enhanced local contrast on it and that, as I have mentioned several times, looks a lot like what you get when sharpening has been used.
If the images came from your sony then it may have had some of that sort of sharpening (aperture correction type) treatment. Yes, at half amplitude peaks are the same width but there, the similarity ends. Am I totally raving or is this a valid point?

You seem to have been so busy taking offence at my harmless remarks that it is only now that you seem at all receptive - please don't stop.

 

[Andy Resnick]

I'm not sure which is the case- that I've not been clear enough, or that you are insisting on an indefensible position.

I thought I was being very clear all along- single chip color cameras are not appropriate for quantitative image analysis. Pointing to 'data' obtained from a single-chip color camera image and treating that as quantitative information is a bad idea.

My goal of the image comparison was simply this- images from a single-chip color camera that appear grossly different, sometimes cannot be easily distinguished by pixel peeping.

Maybe I am not understanding your position. In that case, I would suggest that you post some images of your own to illustrate what you are trying to say.

 

[sophiecentaur]

My only 'position' is more or less is in total agreement with the third para of your last post. But, from the large number of pictures you have posted on this thread - plus the graphs, you have been giving me the strong impression that you think that there is, in fact, plenty of objective evidence for drawing all sorts of conclusions.
I have made the point that camera processing is probably responsible for many of the differences in perceived sharpness in pictures - hence my opinion about the use of Raw.

I really don't know why you should be wanting to see images of mine to support my ideas. The ones already posted speak volumes. There is a blow up of the sea, with massive 64pixel blocks of random looking patterns which can hardly be bettered as an example of where jpeg clouds the issue. There is a picture of a distant coastline which is blurred, possibly as a result of the long transmission path over the sea and yet the sparkle of the sea just in front of the coastline is apparently very sharp. Having played many times with Photoshop's Unsharp Mask I know that you can produce exactly this effect with selective sharpening. What use are those pictures in proving or demonstrating anything about atmospheric propagation? Any image that I could submit would be just as pointless.

I think the only pictures that would be worth posting on this thread in order to answer the OP questions would have to be taken on a film camera or a lab camera with monochrome sensor. Bunging a huge imponderable into the signal chain would not be 'good Science', would it?

It would be a pity to find out that we had both, in fact, been shouting the same message but not recognising what the other was shouting.