Picture sharpness and air effects

[sophiecentaur]

Both images are straight off the camera (original shot was in B&W), same aperture setting, etc. (manual focus lens). After capture, both images were treated the same- neither was sharpened.

How do you know what the camera did with its original image if you just trusted its jpeg processing? Those two graphs show that the two pictures differ in more than vertical gain. Consumer cameras do their best to produce a nice picture. They aren't 'measuring instruments'

 

[sophiecentaur]

Maybe I can illustrate the advantage of 12 bits of RAW or more (wasn't it 14?) versus 8 bits JPG as hinted by Borek and Sophie.

Suppose that the metering tells you that this is the perfect exposure setting and that's what you save as jpg:


Obviously the dynamic range here exceeds what 8 bit jpg can reproduce. It won't help much if you increase or decrease the pitch"


You simply lost the information stored in the excess bits, but look what happens if you change the pitch in raw up or down:


See how much information was lost in the jpg.

Now you just need the software to HDR those three together.

It's not for nothing that they sometimes refer to RAW as Digital Negative. You take that 'negative' and 'print it' with various virtual 'grades of paper', you can dodge and burn and a lot of other stuff that will degrade a picture that has already been jpegged.
Raw is the way forward for serious photography. Jpeg is the equivalent of the Instamatic, by comparison.

 

[Andy Resnick]

That's a different problem, one of excessive magnification- even a tack-sharp 35mm image will look horrible if enlarged to a poster-sized print and viewed close-up. That's why medium format cameras are used even for 8" x 10" magazine prints- the magnification is less.

Just to finish this thought- here's the full image field of one of the luminars, projected onto a piece of paper:

[PLAIN]http://img88.imageshack.us/img88/8945/fullimagefield.jpg

For reference, I drew a rectangle on the paper (the small rectangle in the center) the size of a 35mm format image (24 x 36 mm).

Using 300 dpi print resolution, if my camera produces images that can be enlarged up to 20" across, I could enlarge the full image up to 12 feet across and maintain the same level of print quality. In terms of a view camera, using a medium format negative allows a reasonable amount of lens movement to adjust perspective (and film plane adjustment to maintain focus).

 

[Andy Resnick]

Maybe I can illustrate the advantage of 12 bits of RAW or more (wasn't it 14?) versus 8 bits JPG as hinted by Borek and Sophie.

<snip>

Or you could use a density gradient filter in the first place.

 

[sophiecentaur]

And have a special shaped gradient filter for all occasions? I think you need to enter the 21st century, Andy. If you are interested enough to be discussing things at this level you can't justify sticking to jpegs. Pros use RAW for a good reason.

 

[Andy Resnick]

And have a special shaped gradient filter for all occasions? I think you need to enter the 21st century, Andy. If you are interested enough to be discussing things at this level you can't justify sticking to jpegs. Pros use RAW for a good reason.

Until you start posting photos you took, I'm not sure why I should take you seriously.

 

[sophiecentaur]

Until you start posting photos you took, I'm not sure why I should take you seriously.

That's an interesting response. I can't recall, on any previous occasion, being asked, on PF, for personal experimental results, to justify a very reasonable opinion. Did you object to the, perhaps, cheeky wording of my last post. I'm sorry if you were but I thought these conversations were somewhat 'between friends'.

A few minutes on any Photograpy Forum will produce loads of opinions in favour of using Raw format and will provide you with plenty of examples of suitable software. If you have actually used one of the 'modern' image management applications then I would be amazed if you were to say you could tell the difference between the way they deal with Jpeg and Raw formats. If you haven't, then I suggest you give it a try. You will see what I mean.

Can there really be any doubt that data compression before processing cannot produce as good results as processing first and then compressing the data? A 'mechanical' form of pre-processing (a shaped filter mask) would clearly only be a partial solution to the problem of the contrast ratio of an original scene. I don't think you were really being serious, actually.
A few extra bits of quantising must contribute significantly to exposure latitude. Anyone who has used colour reversal film (slides) will know that what you had is what you get. You have nothing like the flexibility that colour negative film will give you. Cibachrome could produce absolutely stunning results - but only from a perfect positive transparency.

http://gallery.me.com/lyner" but not all of high technical quality, of course. Many of the earlier ones were shot in Jpeg.

 

[Andre]

For some more details on the discussion, this may be useful.

Let me just quote the last sentence.

The techniques discussed here work best when full highlight and shadow detail have been captured by the camera sensor in Raw format.

 

[Andy Resnick]

That's an interesting response. I can't recall, on any previous occasion, being asked, on PF, for personal experimental results, to justify a very reasonable opinion. Did you object to the, perhaps, cheeky wording of my last post. I'm sorry if you were but I thought these conversations were somewhat 'between friends'.

A few minutes on any Photograpy Forum will produce loads of opinions in favour of using Raw format and will provide you with plenty of examples of suitable software. If you have actually used one of the 'modern' image management applications then I would be amazed if you were to say you could tell the difference between the way they deal with Jpeg and Raw formats. If you haven't, then I suggest you give it a try. You will see what I mean.

Can there really be any doubt that data compression before processing cannot produce as good results as processing first and then compressing the data? A 'mechanical' form of pre-processing (a shaped filter mask) would clearly only be a partial solution to the problem of the contrast ratio of an original scene. I don't think you were really being serious, actually.
A few extra bits of quantising must contribute significantly to exposure latitude. Anyone who has used colour reversal film (slides) will know that what you had is what you get. You have nothing like the flexibility that colour negative film will give you. Cibachrome could produce absolutely stunning results - but only from a perfect positive transparency.

http://gallery.me.com/lyner" but not all of high technical quality, of course. Many of the earlier ones were shot in Jpeg.

PF is a scientific forum- claims are supported or refuted with evidence, not by appeals to authority or anecdotal evidence.

Again, I have shot 10952 images with my sony (so far), and while 10952 of those images could all be substantially improved, I would be hard-pressed to identify a single image that would be improved solely by a change in file format. As evidence for this, I often post photos here.

None of my scientific images are acquired using the Sony- the Bayer filter, by definition, means that I cannot use those images as quantitative imaging data. I use monochrome focal plane arrays for scientific imaging. Those cameras are calibrated and validated.

You are free to use whatever tools you wish to create an image. Again, and I thought I was being clear about this, in my *personal experience* taking non-science images, I have no use for the RAW data format. *For me personally*, it's not worth the order of magnitude difference in file size or time required to sit and wait for the computer. *Personally*, I prefer to take photos rather than stare at a computer monitor. YMMV.

I don't understand why you are so insistent that I conform to your ideas of what is "best".

 

[Andy Resnick]

For some more details on the discussion, this may be useful.

Let me just quote the last sentence.

A very reasonable article. I focused on the sentence "when seeking the most *realistic* results" (emphasis mine). I honestly don't know what "realistic" means in the context of photography.

Photography is more than simply trying to recreate what you see by eye. If it was, all my images should be blurry and lacking reds and greens :) Photography is also a means to create what I *imagine* I see or to create a scene that is *impossible* to see- here is an example of each:

[PLAIN]http://img27.imageshack.us/img27/2046/8998203090105.jpg

[PLAIN]http://img820.imageshack.us/img820/8479/5828303090105.jpg

In the first image, I wanted to capture the way the moon appears nestled in the clouds like a yellow-red glowing pearl. This is not at all how the scene appeared to my eye- the only thing I could see was the moon in the clouds, the rest of the field appeared black.

The second image could not be seen by eye- the field of view is more than double what our eyes are capable of. Secondly, the sky would be black- I could not see the clouds or horizon.

As a side note for the lurkers, here's a shot my wife took using her point-n-shoot panasonic, all auto setting, etc.:

[PLAIN]http://img33.imageshack.us/img33/757/2572832980105.jpg

The image is unremarkable, to be sure- it's a generic snapshot. Here's a 1:1 crop:

[PLAIN]http://img716.imageshack.us/img716/4518/25728329801051.jpg

The level of detail is good, dynamic range is good, etc. etc. This may not seem to be a big deal, but the camera is a mess- there is sunscreen wiped all over the front lens, the metal lens cover is broken and has to be manually pried open, and is visible in the top-left edge (hence the sunscreen). She didn't any give thought to making the image "look good"- something caught her eye (the transparency of the water) and she pointed and shot. The only processing I did on this image was a contrast adjustment.

My point is that you do not need high-end equipment to produce high quality images- all you need is a clear idea of what you want the photo to look like and some experience learning how to use your camera.

 

[sophiecentaur]

@Andy Resnick
I wouldn't have thought that my comments about the 'best' order in which to perform processing and data compression should need specific evidence at this time. Is there any argument against that? Once a non linearity is introduced, it is very often impossible to correct for all the distortions that have been created. If that statement is in question here then I should have to dig down into established texts. But I think you know what the result would be. You can't undo the jpeg algorithms or every reconstructed picture could be without any of its artifacts.

What you have to say about "Scientific Images" could well be true but it wasn't clear which was which. The reason is not clear why those two ('scientific'?) graphs should look so different in detail. One of them has definite ringing on it - was there absolutely no processing on it at all? The printed pictures look very detectably different because they are different - and in more than just 'gain'. You seemed to imply that the HF content was irrelevant. I made what I thought was a reasonable comment about that. I'm still not clear about your reasoning. How do they relate to ordinary camera images?

On the subject of Jpeg vs Raw. If you can't tell the difference then I can only suggest that your camera must have unbelievable metering, the subjects you photograph are all extremely kind to photo sensors or that you are not highly critical of picture quality.

Having recently moved from a slow to a faster computer, I can sympathise with you if you find the Raw processing takes a while on a slow machine. Personally, I was always prepared to wait on the old computer because it was only on transferring large files (for every picture) and working on a few selected files that time was a particular issue. Feel free to continue to use your Jpeg images but, when you find a really 'good one' - but for the fact that it has its highlights a tad burned out or the shadows lacking any detail - you may reconsider. You really do seem to be a bit more touchy about this than I would have expected.

Your chosen pictures show that there is loads of info in a reasonable picture, taken with some light by a home camera. However, you may not have actually wanted to have that high amount of noise in the purple areas. In the event that you didn't, a Raw version could well have much reduced noise whilst still not burning out the Sun. You have the option.

The picture of the sand was picked, by you, to demonstrate a point. There is plenty of detail in it but what about the colourimetry? Was it as you wanted? How near the original is it? If you don't care about that then fair enough but what if it had been someone's face, under those same lighting conditions? I'm sure you would be more fussy. In which case, a good colour balance adjustment would be very handy. I might suggest that, unless yo are pushed for storage on camera card or hard drive, you could store both versions and work in Raw on the ones you want to 'present'.

You wrote "you don't need high end equipment to produce high quality images". Many images may be pleasant, they may be what you wanted but reliable quality (fidelity?) is another matter. If you are not concerned with this then I wonder why you are posting on this particular thread?

 

[Andy Resnick]

I'm not sure how to respond- I think you are mixing up concepts, or at least not understanding me.

I don't understand why you care so much about what I do.

I posted on this thread because I was directly asked a question.

 

[Redbelly98]

PF is a scientific forum- claims are supported or refuted with evidence, not by appeals to authority or anecdotal evidence.

Members are not required to conduct their own experiments to back up every claim. This is pretty mainstream stuff being discussed in this thread, not some outlandish claims along the lines of faster-than-light travel (just for example).

 

[sophiecentaur]

I'm not sure how to respond- I think you are mixing up concepts, or at least not understanding me.

I don't understand why you care so much about what I do.

I posted on this thread because I was directly asked a question.

Yes, I have had mixed messages, I think. I am still not exactly sure which imaging method is referred to in some of your past posts. What message should be taken from the \scientific' images that would translate directly to ordinary photography?

I am actually interested in the technical matter of those two 'scientific' images and the clear differences between the two graphs. Do you still think that the apparent difference in their perceived sharpness is due to level and nothing to do with the different HF content? I should have said that there is sufficient difference between the two pictures to account for what they look like. Did I miss something? The automatic sharpening in point and shoot cameras is very relevant to subjective performance.

I don't particularly care what you, personally, do about your photographs but I do care that people who read what you write may take you literally and miss out on a useful photographic tool such as Raw processing. You are credited as being a Science Advisor, which would mean that what you write will be taken more seriously than idle chit chat. I, certainly have found that many of the things you write make excellent sense. I feel that you could have qualified your stated preference for Jpeg on the grounds of your colour vision and a slow computer and helped to avoid misunderstanding about its real relative merits. Was there anything else to 'misunderstand' about your comments about Raw vs Jpeg?

 

[Andy Resnick]

Members are not required to conduct their own experiments to back up every claim. This is pretty mainstream stuff being discussed in this thread, not some outlandish claims along the lines of faster-than-light travel (just for example).

Perhaps. But sophiecentaur made specific claims about *my* images.

From the look of the two graphs, it seems to me that the second picture could have had had some 'aperture correction' processing. The slope is increased and there is a slight ringing before and after. That is a common 'sharpening' method which accentuates edges and makes them more noticeable. <snip>

When, as a point of fact, both images were treated identically.

I<snip>Raw is the way forward for serious photography. Jpeg is the equivalent of the Instamatic, by comparison.

This is silly.

<snip>If you are interested enough to be discussing things at this level you can't justify sticking to jpegs. Pros use RAW for a good reason.

This is likewise silly. I'm not a professional photographer, nor have I ever claimed to be one.

Then, after two lengthy posts with detailed explanations about I'm not sure what exactly- proselytizing? cajoling? patronizing? possibly some denigrating...

<snip>

<snip>

which included additional (incorrect) claims about *my* images,I get this:

Yes, I have had mixed messages, I think. I am still not exactly sure which imaging method is referred to in some of your past posts. <snip>

So... why exactly should I be dealing with this foolishness?

 

[Andy Resnick]

Yes, I have had mixed messages, I think.<snip>

Let me ask you this: When I wrote

<snip>
You are free to use whatever tools you wish to create an image. Again, and I thought I was being clear about this, in my *personal experience* taking non-science images, I have no use for the RAW data format. *For me personally*, it's not worth the order of magnitude difference in file size or time required to sit and wait for the computer. *Personally*, I prefer to take photos rather than stare at a computer monitor. YMMV.

Why did you (apparently) interpret that to mean that RAW is a useless format?

 

[Andre]

It's perfectly fine to have personal opinions and to share experiences. Not that I imply that anybody did that, but I think it's also prudent to avoid carefully to spread popular no brainers like go-for-the-glass, when it is obvious that things are much more complex. Then I have a tendency to show that. Like also what useful but hidden information can be stored in RAW.

If you're always happy with jpg and you know what you're missing, sure by all means.

I'm very aware about the bit and time consuming habits of RAW, so for the series of hundreds snapshots on the toddlers birthday party, I use jpg, nobody is interested if the blurred window in the back is washed out or not.

I may use jpg -not always- shooting high dynamic action with 8 frames per second, to avoid the buffer getting saturated after a few seconds, and slowing down the frame rate. JPG continues indefinitely until the battery is empty or the card is full, so that may be a consideration sometimes.

I certainly use raw for studio, macro and landscaping in combination with a small jpg frame, which I use as thumbnail, selecting the best shots, so that I don't have to wait behind the computer for the long time it takes processing all the raws, of which a lot would be trashed anyway.

Luckily the camera allows to store all those very different settings as user profiles, so switching from toddler single snapshots in jpg to a multi frame sequence of a bird in flight in raw, is one click of the dial

 

[sophiecentaur]

@Andy Resnick
Let's forget the Jpeg issue. Do you have a problem with people disagreeing with you in areas of your expertise?

I should still be interested in your comments about the visibility of those two images. For whatever reason, the two graphs are different in detail and so is the image visibility. You are saying it's all to do with level. Is it "silliness" to ask why, when another factor is in play? Could it be something subtle like the way the array is read? No need to be prickly about this one.

 

[Andy Resnick]

Do you have a problem with people disagreeing with you in areas of your expertise?

<snip>

Well, that's exactly the issue here- you haven't said anything to disagree *with*. Instead, you offer reflexive braying about why *my* images are irretrievably degraded and of poor quality, and how I have no business talking about this issue.

Here's a 1:1 crop of a color image I took last night. I cannot detect any meaningful signs of detail loss through data compression:

[PLAIN]http://img839.imageshack.us/img839/4546/dsc10251.jpg

And before you confuse the data compression associated with displaying the image here with the actual image, here's a 1000% crop of a region of the above image. Where, exactly, is the dreaded loss of information from data compression?

[PLAIN]http://img801.imageshack.us/img801/9494/dsc102512.jpg


Again, my issue is simply that you are making unsubstantiated claims about *my* images.

While this "conversation" has been going on, I've taken 200 photos. That would be 20 GB of uncompressed data to deal with. In a week. Every week. That is not how I want to spend my time, especially since I have so much to learn about composition, lighting, and creating a photograph that can clearly communicate an idea. Pixel peeping is *way* down on my list of priorities.

The only expertise I have proffered here is in regards to the analysis of optical systems- not the design of optical systems, and certainly not the post-processing of images.

 

[sophiecentaur]

I liked the "braying" comment. You really are ratty about this aren't you. Why? All the pictures (all pictures) have faults and is there anything wrong with pointing them out? This isn't a Photo Forum and there is no artistic evaluation of any of them in my comments. Why be so precious when I say that I can see noise and probable colour mismatch? You have said tht you have non-standard colour vision so why be surprised that someone can see something in a picture that you cannot? If you really aren't concerned with quality then why not just use your 'phone - or your Wife's camera.

The picture of the Moon - very nice to look at - has low contrast and low detail, as one might expect from a non-NASA image. JPeg doesn't need to work very hard to compress it so there are no visible artifacts. We all know the sort of picture that Jpeg slaughters and that blowing up pictures of fine structures like nearby trees against the light will crawl with visible artifacts that won't be there in RAW. You seem to be wearing two hats for this thread. Your 'science' hat is objective but your other 'Photographer' hat seems to make you a tad more sensitive than is useful. Why are you offended by valid comments about pictures just because they happen to be yours? I do the same and worse to my own and I don't kid myself that they're high quality when they're not.

We will just have to draw a line under that one. But, I would still like to see an objective response to my comments about the b/w images and the graphs. I ask again why you say the difference in apparent detail is just due to level when the hf content is so clearly (no?) different, according to the graphs. There may be a good answer and I should be genuinely interested to know.

 

[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.