Preventing anomalies

Discussion in 'Seeking Critique' started by G&R, Feb 11, 2021.

  1. G&R


    Sigma 70-300 DG macro.
  2. William Michael

    William Michael Moderator Staff Member

    thanks... did it have a filter on it?
    Last edited: Feb 16, 2021
  3. G&R


    There was no filter on it.

    The DG seems have a filter inside it though, and I say that because the colour produced by a DG is the same as a the colour produced by Sigma DL only when a DL has a skylight added!
  4. William Michael

    William Michael Moderator Staff Member

    I dug this out of my digital library - LINK

    Using the slider at the bottom of the graph, you can see how the combination of using F/5.6 and FL = 300mm provides the worst of the CA for that lens.

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  5. G&R


    How annoying. Maybe I would have been better off using an auxiliary with the kit lens.. :(

    That is a really useful graph. Are there similar graphs for other lenses?
  6. William Michael

    William Michael Moderator Staff Member

    Probably better having in the back of your head that the lens in question has two main (basic) design features:

    1. it is a ZOOM Lens

    As generalizations:

    A. we can expect that zoom lenses perform at their worst at the extremes of their zoom range: CA typically at the long end, Vignetting at the wide end; (two examples only of lens's technical performance factors)
    B. we can expect a lens to perform at its worst at the extremes of the Apertures: CA typically when wide open, Diffraction when fully stopped down; (two examples only of lens's technical performance factors)

    Hence - with the gear you had - from a totally TECHNICAL CRITIQUE - probably better to have PLANNED to:
    > bump the ISO
    > stopped down to at least F/8, F/11 if you could manage
    > shortened the shutter speed
    > pulled the shot at FL = 200~240mm, even if doing so meant a small crop in PP


    Have a look at other on line reviews have some too.

    Personally I hardly ever look at graphs; I find making photos much more fun. That happened to be one of several graphs I reference when teaching Practical Basics of Lens's Use - it just happened to be the lens you have and it just happened to be the sample graph I have referenced for thinking about CA when using a short to mid telephoto zoom.

    There's nothing 'wrong' with your lens. Sure, arguably a Canon 70 to 200 F/2.8L zoom would do better, but those three L Series lenses have limits, also.

    One of my technical tasks has always been to understand those limits so I can best utilize each of my lenses and push the limits if I need to.

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  7. And we’re all newbies in this regard. The main advantage conferred by the accumulation of knowledge, skill, and experience over years is discovering how little we know.

    Each of us is well served by the intellectual curiosity to figure out why what happened happened. On more than a few occasions, I’ve discovered how I erred during capture by discovering what made it better in post processing and/or by seeing the effects of various manipulations. Playing with suboptimal images is often enlightening, fun, and educational.
    dcstep likes this.
  8. I agree, but ultimately it becomes a waste of time, except in rare circumstances. Some people never learn to make great images because they've gotten addicted to fixing crap. I think that I misunderstood our OP and didn't really understand until later that he was asking about the CA in the sample image. Even the very best software can't fix bad CA, which often results when using "kit" lenses. Canon, for example, includes some horrid lenses in some of their entry level kits, only fixed by buying a better lens.
  9. Otis wasn't talking about "some people." He was talking about himself, thus the use of "I've" in I’ve discovered how I erred during capture by discovering what made it better in post processing and/or by seeing the effects of various manipulations. Playing with suboptimal images is often enlightening, fun, and educational.

    My own experience is this. I started out thinking I could fix crap and by doing that I really honed my post processing skills, even though I didn't get much lemonade from the lemons I worked on. More often, I was able to compensate not for utter crap but for some things that happened in capture that needed further work. I'm not much of a purist, so if I don't get a result I'm completely ok with out of the camera I'm quite fine seeing if I can achieve something suitable with some post processing work. That valuable experience resulted in 1) my learning, by my own experience, that post processing wasn't really a fixit tool for garbage, and 2) my refining post processing skills that I could now put toward expressive use on photos that allowed whatever post processing I deemed appropriate.

    I liken it to practicing scales on the piano, though in select ways. If I practiced too much finger technique and technical "chores" on actual pieces of music, those pieces could sometimes lose their luster for me and the musicality could be muted by all the exercising I'd done on them. If I did the exercising with scales, however, then I could put all my aesthetic and expressive effort into the musical compositions when I got to them, the finger technique having become more second nature via the scale work. And, sometimes, I did just the reverse, which was to try and give scales as much as expressiveness as I could muster so the exercising wasn't as sterile a place to be as it might otherwise have been. So, learning and practicing post processing on non-keeper photographs, for me, helped keep some of the drudgery (though often a pleasant kind of drudgery) or practice and exercise from the more expressive and personal uses of those very same skills that I put to use on more worthwhile photos.
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  10. G&R


    It may have been overlooked but the opening post did ask for pre-processing fixes. The first edits occur before the camera is turned on, including tasks such as framing the shot, and cropping or other post-production edit is covering-up imperfections. I do crop etc., but it is not an intention to go there.

    When a 6MP camera produces more pixels than most new monitors can display, why are camera makers pushing > 30MPs? o_O
  11. Photographers also make prints, where a lot of things are more apparent.
  12. G&R


    Granted, I am a luddite. I did not consider the feasibility of billboard pixel peeping.

    In my view of the world most photographers will remain amateurs who share images electronically. I wonder how many pixels are in contemporary digital billboards..
  13. The snark is unnecessary. I’m not talking about digital billboards or pixel peeping. I make 8 x 12 and 16 x 20 prints and am glad I have a camera with more than 6 mp.
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  14. So there's all kinds of traps that people fall into between taking an image and "completing" it. For example, I have one wildlife photographer friends that has tens of thousands of unconverted RAW files because he can't spare the time to cull and select the first level of keeper (in wildlife, we may take 1,000 and process 10). Another friend waivers between "realistic" and "artistic" because she literally can't make up her mind. I suggest that she do both initially and if really drawn to the "artistic" interpretation to go back and invest more time to explore fully.

    I've been deep into digital photography since 2007 and I've only tried "recovering" less than a handful of shots and only one of those was worth it because a capture a once in a lifetime image with too low a shutter speed:

    [​IMG]Reprocessed Blackbird On Owl Shot (Explored) by David Stephens, on Flickr

    The OP has come back and let us know that he was interested in pre-processing thoughts. I gave those in my initial posts on this thread.

    My point of view is colored by my wildlife photographer perspective, but it's bled over into my Street and Travel photography. I still go for an "accurate" interpretation, starting in-camera, trying to tell a story, but doing very little post-processing. I mainly adjust color temp, or occasionally convert to B&W, adjust Shadows, adjust Highlights and Crop. I'll Clone out distracting objects, but that's more so a wildlife thing than with Street or Travel, where I try to crop in-camera, but I'll allow some room around subjects sometimes, in anticipation of a later crop.

    I'm processing almost every day and have a full-time job (financial risk consultant), and my goal is usually to be "realistic", so I'm not looking to roll around in an image and try to make it into something that it's not; however, I understand that point of view and know some people that really enjoy that. I thought that our OP was coming from my more "realistic" POV from his first post.
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  15. That's not what post processing has to be about. Post processing, for me, is about making the photo what it IS. I don't consider a photo to start out as something and then get transformed into something that it was not. My "process" starts at the moment of capture (or before if I've done some planning) and ends when the print is hanging on the wall or shared via the Internet. What it IS is a process that seems to end when I share the picture, which is what people see when they look at what's there in front of them.

    My goal may be to be realistic sometimes, to be expressive sometimes, to be creative sometimes, and there's plenty of overlap. Ultimately, I'd say my goal is to be photographic. This means, for me, to take what the camera gets pointed at through all the stages and manipulations that cameras, lenses, perspective, lighting, focus, and post processing may include and come up with a picture, a picture which may closely represent reality or not, depending on the case. If I want to meander from accuracy, there are many ways to do that, via perspective, framing, lighting, exposure settings, aperture openings, and post processing. But, for me, it's all what it IS.
    dcstep likes this.
  16. So the main culprit here is a crappy lens with high CA. Also, 1/180s shutter speed is too slow for (a) 300mm focal length on a crop sensor body (sans IBIS) and (b) for small birds that are constantly moving.

    Don't know whether the image as posted has been cropped from the original - if so, then 10MP isn't much to begin with.

    Yes. And No. Flash might help freezing the motion and bring some desired catchlight into the bird's eye (as well as some more light onto the subject as well). Trouble with using flash is that it either requires setting the camera to the usually rather slow sync speed (rarely faster than 1/320s and often only 1/250 or even 1/125) - now one totally relies on flash freezing subject motion and blur induced by camera motion. Or one needs HSS (high-speed sync) which significantly reduces flash distance (despite the fresnel-lens flash extender in front of the flash). I had my period of using flash in bird photography but have long since given up carrying one as in most cases it isn't more than a rather insufficient fill-flash. In addition, with many birds, using flash gives you a one-shot opportunity as most birds take off the instant the flash goes off. Whether or not the flash actually hurts the bird is subject of intense debate; personally, I don't like to have a flash go off into my eyes and simply assume that the bird feels likewise. One goal of any wildlife photographer IMHO should be not to disturb the subject to get the shot - another reason not to use flash as it certainly gets you noticed.
  17. William Michael

    William Michael Moderator Staff Member

    Disagree with the (implied) emphasis/nuance - I think this is an important point -

    As I believe I have pointed out, and reiterate now for clarity - the lens is quite capable and it actually presents with CA which, for the most part, is unremarkable.

    Apropos the presentation of CA in the sample image: the (two) main culprits where the Aperture chosen and the Focal Length chosen - both these combined rendered the lens at its worst CA.

  18. OK, so to clarify: crappy for the intended application "bird photography" - which likely forces the use of the longest focal length and fastest aperture in most cases - just the scenario that brings out the worse in this particular lens. In my experience, 300mm - even on a crop sensor camera - is quite limiting. And at 300mm, the lens does not perform well (not only for CA but resolution as well) - both in the test you linked to above and in others I've seen. The lens is indeed quite capable between 70 and 200mm, especially given its price point.

    The lens' performance actually reminds me a lot of the Nikon AF 75-300mm lens I started bird photography with - quite capable up to 200mm, and not so much beyond. Though CA never got as bad as with the Sigma. Yet the lens proved quite unsuitable to produce satisfactory images at or near its longest focal length (unless stopped down to f11, which is not an aperture one can use often in bird photography).
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  19. William Michael

    William Michael Moderator Staff Member

    Yes, Dieter, I agree entirely with your clarification and expansion of the all the point and the comparison you make to a 70~300 Nikon (could easily be Canon also). Thank you for replying.

    Not the best lens choice, for this particular job: and, the factor of price point is usually relevant in mostly all circumstances.

  20. G&R


    What is annoying about the Sigma's limitations at 300mm is that the Sigma's macro focus only works at 300mm. It is also a heavy lens and a lot of bulk to carry, so if its not all usable then it might as well never be used. Many of my other lenses can reach 200mm and I now feel obliged to work through them diligently to identify which lens has the longest usable focal length.
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