Home News Buyers Guide About Advertising
 
 
 
   
Results 1 to 9 of 9
  1. #1
    Join Date
    Aug 2005
    Posts
    363

    calculating shutter speed

    Hi all. Just a few basic queries on shutter speed. The rule of the shutter speed is that it should at least be minimum the inverse of the focal length- ie; if I zoom to 200 mm the shutter speed should at least be 1/200. In low light at home I use aperture priority, open aperture fully , up the iso to 1600 and zoom to 136 whicih is the max on the canon 17-85 lens then the shutter reading says 6 which is one sixth of a second right? The rule of the inverse does not work then? I may be asking a very basic stupid query, forgive me for that .
    Dr Krishna Raman

  2. #2
    Join Date
    Mar 2005
    Location
    Georgetown, KY
    Posts
    1,627
    I think what you are what you are talking about is the "rule" for handholding to keep from blurring. It doesn't hold true for exposure. Hope this helps.
    Dennis

    Canon 5D
    Canon 20D


    Georgetown, KY Photographer
    Retouching

  3. #3
    Join Date
    Jul 2004
    Location
    Grafton, MA
    Posts
    1,714
    In AV mode, the camera will choose the shutter speed based on the exposure that the camera calculates (i.e. how much light is reaching the sensor). So the reason the camera is choosing 1/6 as the shutter speed is because the light requires it for proper exposure. You can get more light to the sensor by opening up the aperture (choosing a smaller f-stop) or upping the ISO. Since you are already at ISO1600 the only option is to open up the aperture. If you are at your widest aperture, your ISO is at 1600, and you are still getting 1/6 for a shutter speed, then it's time to turn on your flash!

    The "shutter speed should be the inverse of the focal length" rule applies to how low a shutter speed you can handhold a lens at before your images begin to blur from camera shake. So if a 50mm lens is 80mm on a digital body, you should have a SS of 1/80 to get sharp results handheld. The IS on your lens helps with the camera shake allowing you to handhold at much lower shutter speeds, though I think you'll probably still get some camera shake at 1/6!
    www.jamisonwexler.com

    Canon 5dII|Canon 5D|Canon 40D|Sigma 15 f2.8|Canon 35 f1.4|Canon 50 f2.5|Canon 50 f1.8|Canon 85 f1.2|Canon 17-40 f4|Canon 18-55 f3.5-5.6 IS|Canon 24-105 f4 IS|Canon 28-105 f3.5-4.5|Canon 70-200 f2.8 IS|Canon 75-300 f4-5.6 IS|Kenko 1.4x TC|Canon 580ex X3|Canon 380exII |Canon 420ex|Sunpak 383 x4|Sunpak 120j x2|Sunpak 622|Elinchrom Skyports

    Past Gear

  4. #4
    Join Date
    Aug 2005
    Posts
    363
    Thanks everyone. Going by what Jamison says there is no point in non flash shots unless one has a tripod when shooting indoors ( unless of course one has a F 2.8 as the max aperture). Unfortunately I did try to buy the Tamron 28-75 F2.8 but that copy was front focusing so I gave up and went for the canon 17- 85 canon instead . I also bought the new 70-300 IS and should admit that its very sharp outdoors so far. Need to experiment on different apertures and sceneries though.
    Dr Krishna Raman

  5. #5
    Join Date
    Nov 2004
    Posts
    1,807
    f2.8 won't always do the trick indoors either. had the tamron 28-75 and sold it - because of AF problems, but in using it i also realized how inadequate f2.8 can sometimes be indoors. primes are great for this purpose but shallow DOF limits the use to mostly single subjects and AF needs to be accurate. also have a canon 70-200 f2.8 L but it gets difficult to get hand holdable shutter speeds past the wide end. i can see why wedding photos need the IS version. bounced or diffused flash is still the best option for most indoor shooting IMO (when it's not prohibited that is )
    canon 17-40 L, 70-200 f2.8 L, 400 f5.6 L, 50 f1.4 & f1.8, 1.4x TC, sigma 15 f2.8 fisheye, flash 500 DG Super, kenko extension tubes

    note to self: don't participate in sad, silly threads unless you're looking for sad, silly responses.

    "anti-BS filter" (from andy): http://dcresource.com/forums/showpos...94&postcount=4

  6. #6
    Join Date
    Dec 2004
    Location
    Los Angeles, CA
    Posts
    3,109
    I woke up thinking about this this morning (you can see I really need to get a life if this is what I wake up thinking about ): what we need are digital cameras with more sensitive chips. One of the biggest disappointments when i first got my XT was I didn't get photos that looked like what I was seeing in my viewfinder. Having come from a Panasonic FZ20 which has an electronic viewfinder, with that camera what you saw was what you got. With the XT (and all DSLR's) what you see in the viewfinder is NOT what you get. Now I understand the limitations of CCD/CMOS technology and in effect most digital chips (still and video) have a 5-6 stop dynamic range and a relatively low overall sensitivity to light, whereas film can have up to 12 stops of DR and is more sensitive to light, and the human eye has like the equivalent of 20 stops and can see in all but the darkest of conditions. But the point is, when I see a beautiful tonaly (don't know if that's a word) composed shot full of highlight and shadow detail through my DSLR viewfinder and then see the actual image the camera records, uggh! What a disappointment. Of course having used my XT for nearly 9 months and taken nearly 25,000 photos, my expectations have shifted dramatically. I no longer expect a photo that matches what my eyes see and I can now almost see the shot as the camera will record it rather than what my eyes are seeing. But I can't help but wonder what a camera that delivers at least film-like DR and light sensitivity would do to the digital imaging world. I suspect (but don't really know for sure) the original engineers of the CCD techology were aiming to emulate the sensitivity of photographic film when they designed their chips. But what if they aimed for the sensitivity of the human eye - both in terms of overall sensitivity to light and dynamic range.

    The reason I'm posting this morning's ponderings here is a more sensitive chip would allow higher shutter speeds in lower light conditions. I often see a beautifully lit scene with my eyes only to find that the camera registers an absurdly low shutter speed which means I need to add some flash which completely ruins my vision (or perhaps the vision of my subject if I'm close enough or if I'm using the internal on-camera seizure inducing AF-assist strobe on the XT - now what the hell were they thinking???? ) But I digress...

    No doubt those same engineers are busy churning away in the their labs trying to design the next generation imaging chips that do come closer to replicating what my eyes see when looking through the viewfinder. And no doubt it will be a happy day in my photographic life (though perhaps not in my pocket book) when such a device arrives. But until then I'll keep churning away in my little world, adding flash here, turning up the ISO there, and then dodging and burning away the midnight oil on my computer...
    Last edited by 24Peter; 01-06-2006 at 07:47 AM.
    Canon A720 IS, 40D w/ BG-E2N, 28 1.8, 50 1.4, Sigma 70 2.8 macro, 17-40 F4 L, 24-105 F4 L IS, 70-200 F4 L IS, 430 EX, Kenko 2X TC & Ext Tubes, AB strobes and more...
    View my photo galleries here: imageevent.com/24peter

  7. #7
    Join Date
    May 2005
    Location
    Crapville, Australia
    Posts
    5,148
    You seem to be addressing a few different points here namely:

    1) Sensitivity. Well all you need to do is crank up the ISO. The latest Canons perform very well at over ISO 800 and I suspect there will be even more improvements to come in this area. Up until around six months ago I was using Kodak T-Max 3200 (rated at 1600) for my ambient scenes at wedding receptions - the same ISO on digital is a lot less grainy/noisy.

    2) Dynamic Range. I'm not sure where your thinking is here but digital has greater DR than film. Reversal film has about 5-stops DR. Negative has about 7-stops. Many digital SLRs are capturing around 10-stops of DR. With non-standard development and exposure, B&W neg can potentially capture a greater range (eg; extreme zone system application) but that's a pretty specialised area. Incidentally, publishers require around 4-stops of DR only which is one of the reasons why colour reversal was popular for reproduction - anything outside this range couldn't be reproduced in print anyway. Same with RA-4 print, only about 5-stops here too. In some ways those extra stops of DR are kinda useless, but it does give you a good safety net if you don't nail the correct exposure (and if you shoot RAW it does allow you to overexpose slightly to use more bits for rendering shadows prior to conversion) - or you just want to view on a high DR monitor.
    Last edited by cwphoto; 01-06-2006 at 05:24 PM.
    Christian Wright; Dip Phot
    EOS 5D Mark III | EOS 600D | EOS-1V HS
    L: 14/2.8 II | 24/1.4 II | 35/1.4 | 50/1.2 | 85/1.2 II | 135/2 | 180/3.5 Macro | 200/2.8 II | 400/2.8 IS | 16-35/2.8 II | 24-105/4 IS | 70-200/2.8 IS II | 100-400/4.5-5.6 IS
    580EX II | EF 12 II | EF 25 II

  8. #8
    Join Date
    Aug 2005
    Posts
    363
    Being a doctor, I think the human eye and brain can never be equalled. However much technology improves a live organism is always superior. We associate emotions to the things we see and hence the joy of seeing it is better unlike a camera which is just a machine. I guess the best option is to use a tripod/ flash if permitted and then indoor shots are not a problem. But why do you say that F 2.8 always may not work. Is it not true a 2.8 gives clean crisp subjects in focus? unless one wants a different perspective?
    Last edited by mediyoga; 01-07-2006 at 02:21 AM.

  9. #9
    Join Date
    Nov 2004
    Posts
    1,807
    Quote Originally Posted by mediyoga
    But why do you say that F 2.8 always may not work. Is it not true a 2.8 gives clean crisp subjects in focus? unless one wants a different perspective?
    i guess this part is addressing me. what i mean to say is that many times i don't get enough light with an f2.8 aperture. indoors, using f2.8 USUALLY means shutter speeds of about 1/50 to 1/60 at ISO 800 or 1600. not quite fast enough for moving subjects or hand holding medium-tele focal lengths. i don't like the noise at 1600 either. with the 50 f1.4 for example, i gain 2 whole stops which means i can double my shutter speed and lower the ISO to the 400-800 range. it still doesn't work out too well for moving subject because of shallow DOF though. with an external flash i can use ISO 400 or below, deep DOF if i want it, freeze action, AND still get nice looking lighting.
    canon 17-40 L, 70-200 f2.8 L, 400 f5.6 L, 50 f1.4 & f1.8, 1.4x TC, sigma 15 f2.8 fisheye, flash 500 DG Super, kenko extension tubes

    note to self: don't participate in sad, silly threads unless you're looking for sad, silly responses.

    "anti-BS filter" (from andy): http://dcresource.com/forums/showpos...94&postcount=4

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •