John Thawley Posted January 8, 2014 Share #1 Posted January 8, 2014 Advertisement (gone after registration) The image of the M camera was taken with my M9. The image of the coffee cup was taken with my M. I'm curious about the odd spots in the bokeh "balls." They are apparent in both images taken with each camera. I'm not panicking or implying there is something wrong with either camera... just curious if anyone has a theory about how these spots appear. ISO was 800 .... lens was a 90mm Summarit opened at f/2.8 for both images. Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/219839-bokeh-anomly/?do=findComment&comment=2504768'>More sharing options...
Advertisement Posted January 8, 2014 Posted January 8, 2014 Hi John Thawley, Take a look here Bokeh anomly. I'm sure you'll find what you were looking for!
250swb Posted January 8, 2014 Share #2 Posted January 8, 2014 A lot of dust on your sensors. Steve Link to post Share on other sites More sharing options...
01af Posted January 8, 2014 Share #3 Posted January 8, 2014 A lot of dust ... Yes. ... on your sensors. ... on your lens elements. Link to post Share on other sites More sharing options...
John Thawley Posted January 8, 2014 Author Share #4 Posted January 8, 2014 Yes. ... on your lens elements. That would be an easy solution... if it were correct. Why isn't it apparent anywhere else on the image? And FWIW... I highly doubt dust on the lens (or sensor for that matter) would be visible at f/2.8. These spots are fairly well defined. Link to post Share on other sites More sharing options...
John Thawley Posted January 8, 2014 Author Share #5 Posted January 8, 2014 FYI... the M camera was "minutes" old. John Link to post Share on other sites More sharing options...
Guest Holy Moly Posted January 8, 2014 Share #6 Posted January 8, 2014 just repeat a sky shot at f16 Link to post Share on other sites More sharing options...
aesop Posted January 8, 2014 Share #7 Posted January 8, 2014 Advertisement (gone after registration) ...my layman's reasoning tells me the 'spots' have something to do with the bright highlights and the way they are rendered - in both instances (taken with different cameras) the spots do not appear elsewhere. Link to post Share on other sites More sharing options...
250swb Posted January 8, 2014 Share #8 Posted January 8, 2014 The orbs containing the image of the dust spots are not soft, they are focused, and so they either project an image of spots of dust in the lens onto the sensor, or 'project' a focused light and cast a shadow of dust that is on the sensor (as happens with showing normal sensor dust up by closing the lens down to f/16). It is unlikely to be dust in the lens as the spots are well defined, so it's dust on the sensor, don't be confused by the lens being wide open, but that is why they don't appear anywhere else in the pictures. You didn't answer if you'd ever cleaned your sensors, but even for your M at a few minutes old it isn't unknown for new cameras to have dust and oil on the sensor. It is the worst time for dust, it gets shaken out in transit and while the components are bedding in. Steve Link to post Share on other sites More sharing options...
John Thawley Posted January 9, 2014 Author Share #9 Posted January 9, 2014 So.... here is a white wall shot at 1600 ISO f/16 using the same lens and the M body... several weeks and about 1000 frames since the coffee cup photo was taken. I marked the two spots I could find. Please note, I'm not trying to be adverserial... I just don't believe the spots in the images are sensor or lens dust. My theory is they are projected defects found in the cheap glass ... both material and manufacturing .... of the christmas tree lights. The bokeh balls (dimmer ones) also show a lunar surface type pattern in them too. Further... just to qualify my personal and professional background, I shoot motorsports for a living... over 70,000 frames per year. I'm pretty comfortable around a sensor and sensor cleaning. John Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/219839-bokeh-anomly/?do=findComment&comment=2505073'>More sharing options...
01af Posted January 9, 2014 Share #10 Posted January 9, 2014 Please note, I'm not trying to be adverserial ... I just don't believe the spots in the images are [...] lens dust. Carefully look at the rims of the blurred highlights ("bokeh balls")—what do you see? Link to post Share on other sites More sharing options...
John Thawley Posted January 9, 2014 Author Share #11 Posted January 9, 2014 Here's a 100% crop at about 85% size due to forum posting restrictions. Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/219839-bokeh-anomly/?do=findComment&comment=2505093'>More sharing options...
jdlaing Posted January 9, 2014 Share #12 Posted January 9, 2014 What is the light source of the spots of light? Link to post Share on other sites More sharing options...
adan Posted January 9, 2014 Share #13 Posted January 9, 2014 1. The bokeh circles themselves show hard bright edges - what is considered (or so I understand, I don't put a lot of time into bokeh) "nisen" or double-line bokeh. Overcorrection of spherical aberration in order to produce the best possible focused image (at the expense of harsher blurs if the background lighting is such as to promote contrasty bokeh - fairy lights, or small bright points of sky seen through foliage). 2. The smaller blobs also show edge effects ("target-like" which gives the impression of some kind of diffraction effect (which could be quite likely if we are talking about things as small as dust specks). Or the kinds of outlines found in Schlieren photography or phase-contrast microphotographs. http://st5.divshare.com/launch.php?f=5690435&s=008&i=normal http://www.asylumresearch.com/Gallery/BioScience/Optical/PhaseContrast/PhaseContrast!.jpg 3. The dust specks (if that is what they are) are NOT on the sensor - a whole different look, as well as being far too numerous, and not showing in the pure white wall picture. I expect this is simply an effect of light rays (or particles, as one prefers) doing some of the weird things lights rays can do when bent and focused and interfering with each other. Not a flaw as such in camera, sensor or lens. There may be a color component to the artifacts, which is not visible in these B&W images. A color image might reveal as such. Link to post Share on other sites More sharing options...
Paul J Posted January 9, 2014 Share #14 Posted January 9, 2014 Spots like these are common in Bokeh and really are from dust, fibre and debris on and in the lens. The brighter edge around the spot is from diffraction caused by the dust. Link to post Share on other sites More sharing options...
pgk Posted January 9, 2014 Share #15 Posted January 9, 2014 I expect this is simply an effect of light rays (or particles, as one prefers) doing some of the weird things lights rays can do when bent and focused and interfering with each other. Not a flaw as such in camera, sensor or lens. I've come across this effect myself and it occasionally occurs if wearing spectacle in certain lighting conditions when images, with those dark diffraction halos, of debris (dust and hair) on the spectacle lenses appear to get projected onto the back of the eye. In photographic situations all it does is tell us that there is some dust (inevitably) on or in the lens being used, which is nothing to worry about. I'd be interested to know what the theory is behind how it occurs but have never come across an explanation. Link to post Share on other sites More sharing options...
adan Posted January 9, 2014 Share #16 Posted January 9, 2014 Some other observations - not about the spots as such, but about other "effects" noticeable in the imaging, which just go to show what defocused point light sources can do: - In the cup picture, there appear to be horizontal streaks in the faint blur circles, just above the blurred magazine pages, and directly to the left of the word "Dreams". I'd love to see that area enlarged. - In both pictures, right at the point where the table meets the bright blur circles - the table edge is defocussed and blurry, and the background lights are defocussed - yet the background circles are cut off with a hard, sharp edge. I've run across this "sharp within blurry" effect myself. For example, this section of a portrait: Focus was on the forehead hair, and the hair on the head then gets progressively blurry as it moves into the background... ...EXCEPT where it crosses the bright blur circles in the background (left and top right), where the more distant hairs are suddenly "sharpened" by quasi-collimated light from a bright point source in the background (itself blurred). (M9, 75 Summarit @ f/2.5) Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/219839-bokeh-anomly/?do=findComment&comment=2505250'>More sharing options...
keithu Posted January 9, 2014 Share #17 Posted January 9, 2014 Carl Zeiss have a paper available about lens bokeh which covers this phenomenon: http://www.zeiss.com/c12567a8003b8b6f/embedtitelintern/cln_35_bokeh_en/$file/cln35_bokeh_en.pdf Page 32 is particularly relevant. You're seeing images of dust and surface imperfections of the lens elements. Link to post Share on other sites More sharing options...
pgk Posted January 9, 2014 Share #18 Posted January 9, 2014 Carl Zeiss have a paper available about lens bokeh which covers this phenomenon: http://www.zeiss.com/c12567a8003b8b6f/embedtitelintern/cln_35_bokeh_en/$file/cln35_bokeh_en.pdf Page 32 is particularly relevant. You're seeing images of dust and surface imperfections of the lens elements. I'm not so sure about this (I'm familiar with the paper having downloaded it previously). 'Backscatter' is a well known problem in underwater photography (although I've never heard it referred to as 'orbs'!) and can features something similar to 'diffraction imperfections' but certainly not all that often (small apertures are used which might explain this). But I'm not sure that the explanations given are actually directly relevant to the OP's images which seem to show internal (?) dust causing spots rather than surface dust (perhaps John could comment on the state of his front element;)) or airborne dust, and page 32 refers to soft focus filters - ie something in front of the lens rather than on or within it. It looks like there may be similarities but I'm not convinced that the effect is the same. Link to post Share on other sites More sharing options...
adan Posted January 9, 2014 Share #19 Posted January 9, 2014 I think keithu means the picture in the left column of p. 32 of that Zeiss article - showing the "fingerprint" (literally) of pressed aspheric lens production (as concentric circles within the blur circles) as well as a couple of spots similar to the original post here. I first noticed that aspheric fingerprint - ironically - using the Sony R1 with a Zeiss 14-70 zoom (with aspheric elements). Link to post Share on other sites More sharing options...
mjh Posted January 9, 2014 Share #20 Posted January 9, 2014 That would be an easy solution... if it were correct. Why isn't it apparent anywhere else on the image? And FWIW... I highly doubt dust on the lens (or sensor for that matter) would be visible at f/2.8. These spots are fairly well defined. Your reasoning applies to the image plane. The circles of confusion are caused by tiny specks of light well beyond the depth of field, and with repect to these bright highlights the sensor is far from the image plane. What we’ve got here are not images of the subject; rather the circles of confusion are images of the aperture, i.e. images of the inside of the lens. Link to post Share on other sites More sharing options...
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