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Thread: Is my use of a filter(UV) contributing to difficult focusing?

  1. #1

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    Is my use of a filter(UV) contributing to difficult focusing?

    Hello,
    I take images of Fastjets and experience difficulties with obtaining good images. I have a filter on my lenses, 'cos I have always (30+years) used a filter "to protect" the lens.
    My equipment is a Pentax K-7 and a Sigma 150-500mm F5-6.3 lens.
    As an optimist, I shoot at subjects moving at speeds ranging from 100-500 mph and at distances up to 6000ft.

    Why do I have a Pentax and not a Nikon/Canon? Historical collection Pentax film lenses from the old days which can be used in manual mode on DSLR Pentaxes. The main reason is that I assumed that 35mm film cameras and DSLR had a direct relationship with image size. A Pentax 645 should have been my starting point! !

    (Well, that has got that off my chest, I don't feel so daft any more). As there are no pockets in a shroud, perhaps a Canon EOD 5D Mk3 and matching lens will be a good move?

    All comments and advice will be welcome.

    P.s. I plan to shoot some images of military helicopters next week, they tend not to move so fast.

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    Moderator Donald's Avatar
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    Re: Is my use of a filter(UV) contributing to difficult focusing?

    No!

    What is causing the problem? I don't know. But it is not through having a UV filter on the front.

    Do you feel confident in terms of understanding the challenges of consistently obtaining good quality photographs in such circumstances. It is a hugely demanding assignment. In other words, (I hope you don't mind me asking), are you able to exclude the human factor? If so, then it must be technical - focusing speed, accuracy of auto-focusing, etc.
    Last edited by Donald; 15th June 2012 at 08:08 AM.

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    Re: Is my use of a filter(UV) contributing to difficult focusing?

    I believe your lens incorporates image stabilisation and your camera sensor shift ... could they be working against each other?
    The advice I have read tells me to pick one or the other, not both, as I have only recently bought a sensor shift camera and using OIS lens with it.

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    Re: Is my use of a filter(UV) contributing to difficult focusing?

    I don't know a lot about your hardware, but in the Canon camp, one needs to change the IS mode if panning whilst shooting to avoid "issues" - not sure if your hardware has the same requirement?

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    Re: Is my use of a filter(UV) contributing to difficult focusing?

    Quote Originally Posted by jcuknz View Post
    I believe your lens incorporates image stabilisation and your camera sensor shift ... could they be working against each other?
    The advice I have read tells me to pick one or the other, not both, as I have only recently bought a sensor shift camera and using OIS lens with it.
    Thanks jc but I had that one covered from the start. I have been working my way through images using different parameters and trying to compare the results, the images do not always come out as rubbish, if fact I am quite pleased with many.
    I am working towards elimination of possible causes from the equipment point of view.

    Finger trouble and lack of knowledge on my part have been factored in since day one it is just that someone suggested the filter in a chat the other day, so I thought to ask the experts.

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    Re: Is my use of a filter(UV) contributing to difficult focusing?

    Hello Colin,

    I shoot with the camera IS off and the lens, on. So I will try with both off, is that your suggestion? It will be interesting to see anyway as I have not yet tried it.

    Thanks for your time, I appreciate it.

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    Re: Is my use of a filter(UV) contributing to difficult focusing?

    Quote Originally Posted by C24 View Post
    Hello Colin,

    I shoot with the camera IS off and the lens, on. So I will try with both off, is that your suggestion? It will be interesting to see anyway as I have not yet tried it.

    Thanks for your time, I appreciate it.
    Hi Charlie,

    For normal panning you'll want the lens in Mode II (for Canon) - or switched off if it doesn't have Mode I / Mode II. IS is designed to compensate for camera shake, and they generally just see panning as "one hell of a lot of camera shake" and go a bit weird. If doesn't affect focusing, but the result can look like a focus problem ...

    Is my use of a filter(UV) contributing to difficult focusing?

    Is my use of a filter(UV) contributing to difficult focusing?

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    Re: Is my use of a filter(UV) contributing to difficult focusing?

    Hello Donald,

    I left you until last because you seem wise beyond your years! The filter stays on, thank you.

    Yes, it is difficult but others can and do produce some wonderful images, so with application so will I, god willing. You are correct that it is me but I do not blame the equipment just wondered if the other chap(see other comment) knew what he was talking about.

    This might warrant a new thread, up to you

    Given my current, improving(!) ability and knowledge, am I correct in assuming that a full frame camera would give better images(as shot) and greater scope for post processing than from my P K7? The physics must agree or am I totally loston this too?

    Thanks for the site, it has opened a whole new world and seems to keep the grey/gray cells functioning.

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    Re: Is my use of a filter(UV) contributing to difficult focusing?

    Charlie, I have the dubious distinction of owning a Pentax K7, a Nikon D7K and a Canon 7D. I use each for different purposes. One thing that I can tell you is that, although the Pentax K7 is my favorite walkabout camera, I do not use it at air shows or motor races because the AF just isn't fast enough. In addition, the SR system works well with static shots, but does tend to get a little confused with fast panning. I suggest that you turn all stabilization off, stick to shutter speeds above 1/250th and use a fairly small aperture of around f11 with the camera set to TAv mode. You could also try (horror of horrors) manual focusing. Before the days of AF, there was no other option and I still came home with sharp images!

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    Re: Is my use of a filter(UV) contributing to difficult focusing?

    Unfortunately, I see more posters having problems attempting (for one reason or another) to shoot their DSLR cameras in manual focus than I see posters having problem using auto focus with top-line lenses and good AF cameras..

    Sure, I as well as everyone else shot with manual focus lenses when I used the Canon manual focus SLR film cameras. In fact, I skipped the entire generation of auto-focus Canon film SLR cameras (EOS film DSLR's) because I assumed (it turned out incorrectly) that I, as an experienced photographer, could focus more quickly and more accurately than any auto system could.

    I was wrong; and I want to remind you that the cameras I was using were specifically set up for manual focusing. Today's DSLR cameras ARE NOT specifically designed for manual focusing. It was a LOT EASIER to manually focus using a Canon A-1 SLR film camera, than it is manually focusing with my Canon 7D DSLR.

    Some photographers seem to think that using manual focus or manual exposure somehow elevates them into a more expert level. However, IMO, the level of expertise tends to be determined by the quality of the images captured and presented, rather than in the method of capure...

    My Canon 7D has the best autofocus of any camera I have ever used (I have not used the 1D series cameras to any extent). I am exceptionally happy with the auto focus of my 7D using either the 17-55mm f/2.8 IS or 70-200mm f/4L IS lenses. These lenses work miraculously on my 7D (and are not shabby at all when auto focusing on my 40D and to a lesser extent, my 30D). I use the term miraculously in every true extent of the word. The AF capability of the 7D is mind blowing.

    There is no reason at all that I would ever consider returning to full-time manual focusing, although I do use MF sparingly in such venues as macro work.

    By the way, using the 70-200mm f/4L IS lens in the panning mode (mode 2), can provide exceptional focus speed for fast moving subjects combined with the extra help of IS to maintain sharp imagery. The USM of the two lenses I have mentioned above is super. However, my much older 300mm f/4L IS lens which also has USM capability doesn't fall far behind the 17-55mm and 70-200mm IS lenses.

    My 400mm f/5.6L lens (although it doesn't have IS capability) is also another glass that has exceptional AF capability if combined with a camera that has fast focusing capability.

    Unfortunately for users of the Rebel (series) and 5Dc and 5Dii cameras, these bodies do not have the AF capability which matches the AF of the above mentioned lenses. I am not familiar wit the capabilities of other than Canon DSLR cameras so I cannot remark on those capabilities...

    In answer to your original question, before I went off on this tirade of opinion, I don't think that the use of a decent quality UV or skylight filter should interfere with the focus capability whether that focus be manual or AF. But, I do think that shooting with any type of filter over the lens without using a lens hood can degrade the imagery in many different aspects.
    Last edited by rpcrowe; 15th June 2012 at 05:29 PM.

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    Moderator Donald's Avatar
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    Re: Is my use of a filter(UV) contributing to difficult focusing?

    Quote Originally Posted by C24 View Post
    Hello Donald,

    I left you until last because you seem wise beyond your years!
    Charlie - You are perfectly correct, in respect of a 25 year-old. Unfortunately, for a 57 year old it becomes a different story!

    I hope that what the other guys have said subsequently might answer the question. My understanding of this issue, learnt from other contributors on this site, is that whilst there may be a theoretical (and indeed, an actual) difference, but in the real world of what the likes of you and I are doing, any differences are irrelevant.

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    Re: Is my use of a filter(UV) contributing to difficult focusing?

    Charlie, just some notes from a Canon shooter who has done some air-show work including fast jets.

    Keep the UV filter on.
    Clean the sensor you will find yourself using small apertures.
    Set ISO to 100 to 200.
    Set Tv exposure mode start at 1/1000 to 1/800 for jets (and 1/160 for props) then work down for background blur.
    Set one form of IS only suggest lens since you can see it working in the viewfinder.
    Set continuous focus AF-C
    Goose the shutter button to keep the IS and the focus working all the time.
    Pan Pan Pan
    Practice Practice Practice The tops of trucks / vans on an elevated section of road looking up - is good.
    Set your expectations appropriately few shooters even the very best - get more than about 10% sharp images. Most of us get 1%. Accordingly plan to shoot shed loads.
    Have fun.
    HTH

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    Re: Is my use of a filter(UV) contributing to difficult focusing?

    Just my opinion, but no, a full frame isn't going to be a huge help to you, here. Because whatever you gain in image quality/high iso performance, you're going to lose from the "reach"/crop factor thang.

    Or, put another way, to reach the equivalent of what you're getting framing-wise on a 1.5x crop sensor with 500mm lens, would require a 750mm lens on a full frame camera.

    To me, it's probably not your camera body that's letting you down, here, it's the lens. My guess is that you're having AF issues because of the lens you're using. The Sigma 150-500 OS has a max. aperture at 500mm of f/6.3. Most camera bodies have their AF function compromised when the max. aperture of the lens goes past f/5.6. This is also the same reason that teleconverters can cause AF to go wonky or stop working. The sensor needs a certain amount of light to "see" by to perform autofocus. The max. aperture of the lens determines how much light gets to the sensor during composition/metering/focusing. While you can achieve AF lock, it's probably taking a little longer, and might be a little less accurate, particularly on fast-moving subjects. To me, the one weakness in Pentax's lens lineup is the lack of supertele choices in the native mount.

    Just me, but I'd say try renting or borrowing a Sigma 120-400 f/4.5-5.6 HSM OS, or backing off the long end of the lens until you can get to f/5.6, and seeing if that makes a difference. The main reason a Canon might be a better choice if this is your main subject for shooting is that you'd be able to use to the EF 100-400mm f/4-5.6L IS USM, and that your money might be better spent on that lens than on getting a 5D3. But neither the 7D or the 5DMkIII are weather-sealed the way your K-7 is, and, of course, you'd lose in-body stabilization. And the only Canon pancake lens is the newly announced 40mm f/2.8.

    Oh, and one more thing. You can adapt K-mount/M42 lenses for use on Canon EOS with a simple adapter ring. Maybe not with as much function as using it on a native K-mount body, (no autofocus, stop-down metering, no EXIF, etc.) but you wouldn't have to sacrifice your manual focus glass completely.
    Last edited by inkista; 16th June 2012 at 12:02 AM. Reason: typos

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    Re: Is my use of a filter(UV) contributing to difficult focusing?

    Hi Charlie,

    Well, I was going to reply and suggest a couple of ideas, but Kathy beat me to it on both
    (full frame not helping and f/6.3 being probably too dark for AF)

    Shall I tell you what I hate about airshows (in UK); getting there and getting out again afterwards.
    Last time I went was about 10 years ago, took 3 hours down narrow, gridlocked country lanes - haven't been back to a big one yet - can't face it You're lucky if you're close

    Welcome to the CiC forums from ....

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    Re: Is my use of a filter(UV) contributing to difficult focusing?

    Hi Charlie,
    Just a thought. Are you using A/F on these shoots?
    It strikes me that the autofocus may not be quick enough for jets doing 500MPH @ 600 feet. I'd be inclined to turn it off and pre-focus (Infinity should be fine) and just concentrate on panning.
    On that last point, I presume you are following through on the pan (little golf trick there).

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    Re: Is my use of a filter(UV) contributing to difficult focusing?

    Few more thoughts.

    Back-button autofocus might help by removing AF function from the shutter half-press and putting it on the AF button on the back of the camera. It's typically used by sports shooters so that turning AF on/off won't compete with shooting off frames.

    One more drawback of the Sigma 150-500 is that it lacks a focus limit switch. On a Canon/Nikon supertelephoto, you'll typically find a switch that will narrow the distance range that the AF system will search through to get a lock. A narrower search range means the lens won't focus at certain subject distances, but will AF lock more quickly. I typically use it (and back-button AF) when I'm shooting birds in flight.

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    Re: Is my use of a filter(UV) contributing to difficult focusing?

    Rent a 7D and the EF400F/2.8L IS USM and the x1.4MkII tele-Extender EF - and use a Monopod.
    Rent that gear for long enough to learn the Lens in the type of shooting you are doing - you will be amazed.
    I am sure the same applies to the Nikon 400/2.8 and a top line Nikon DSLR APS-C but it has been a while since I used Nikon.

    The Sigma lens is just not up to the job you want and will not supply the keeper rate you require - the lens is too slow (max Aperture too small): and that's the alpha and the omega of it - and then the Canon (and Nikon) lenses have enhancement features specifically to nail keepers in fast action shooting (some already mentioned by Kathy Li).

    WW

  18. #18

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    Re: Is my use of a filter(UV) contributing to difficult focusing?

    Good day to you all and many thanks for your thoughts and suggestions. There is a lot here to digest, so I will take some time to mull [Donald?] it over.


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    Re: Is my use of a filter(UV) contributing to difficult focusing?

    Canon has several lenses which are very good for airshow work while the Canon 7D and the 1D series cameras are probably the best camera choices for any action shooting. I personally prefer the 7D because I like to carry a pair of cameras and the 1D (series) cameras are quite a bit heavier than the 7D.

    The 70-200mm f/2.8 IS ii with or without a TC is one choice (although that is quite a pricey option)...

    The 70-200mm f/4L IS lens is a less expensive and lighter weight option. That lens works very decently (but not superbly) with a 1.4x TC...

    Whether a 70-200mm focal range would be adequate depends on the distance from shooting position to the subject aircraft. My airshow experience has been primarily at the Marine Corps Air Station Miramar (North of San Diego, CA) and the distance from even the very front row viewing area to the fly-by aircraft is a long ways. Some other airshows, have shorter airplane to spectator distances. It seems that some UK airshows have a shorter aircraft to spectator distance but, that may be my imagination. I have not been to a U.K. airshow and am making that guess predicated on the images I have viewed.

    The 100-400mm f/4.5-5.6L IS lens is a great lens for airshows and for general wildlife work...

    If you can give up the convenience of a zoom lens, the 300mm f/4L IS and 400mm f/5.6L lenses are also quite good for airshows. However, I prefer to have a second camera with a shorter lens such as a 70-200mm (series) for when the 300mm or 400mm focal lengths are too long. I like a combination of 70-200mm f/4L IS and 300mm f/4L IS lenses on a pair of 1.6x cameras.

    I have not used the 70-300mm f/4-5.6L IS lens but, I would expect that this would be a super lens for any airshow.

    I don't know if the in-body stabilization works as well as lens stabilization. I use IS Mode-2 for shooting action since I will often be panning.

    Additionally, the wonderful auto focus capability of the Canon 7D is made to order for fast moving subjects. The AF capability of this camera is really awesome!

  20. #20
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    Re: Is my use of a filter(UV) contributing to difficult focusing?

    For clarity and best understanding of the meaning.

    The sentence:

    “Rent a 7D and the EF400F/2.8L IS USM and the x1.4MkII tele-Extender EF - and use a Monopod.”

    was an indication of what I consider the best option – i.e. taking the extreme to indicate that the poor performance at this job is nearly wholly due to the Sigma Lens.

    There are many other lenses which will out outperform the Sigma lens for this job.

    WW

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