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04-14-2011, 11:15 PM   #1
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Martial arts lens for $300

As the title might suggest, I'm looking for a lens for shooting my kids doing martial arts. I'm using a K200d but I plan to upgrade to a K-5 this year. So whatever I pick I want to keep and use a lot, hopefully. I want to keep the price down so I can actually get that K-5.

Martial arts can be a challenge because the kids are moving fast, wearing white and in bad indoor light. The walls are also pale and using a flash would be considered rude, at least during belt trials or sparring matches.

I tried a Sigma 17-70 which was a little too slow and I no longer own it anyway. The kit lens is OK but not quite long enough and I have to boost the ISO pretty high on the K200. The 50-200 is too long and slow, but I love it outdoors.

My favorite surprisingly is my old M 50mm f/1.7, which is just about the right length and plenty fast. But focusing can be a challenge.

So that is my whole lens collection so far.

At the top of my list is the Tamron 28-75 f/2.8 which I understand equals about 42-112. For this type of shooting it's the perfect length but I wonder how useful it would be in other situations. 42 is a little long for indoor social events right? Plus it's about $400. If I could also use the 28-75 for parties, family events etc it would be a no-brainer. But I think it's a little too long.

I considered some others but I keep coming back to that 28-75. The 18-135 is too slow and pricey. 100mm macro, would work but too pricey. 35mm f/2.4 would work but a little too short. FA 50mm f/1.4 would also work but it's not as flexible as the zoom.

Or maybe long term my kit is the 28-75mm + 21mm limited if I need something wide. I don't mind moving my feet around to get the shot I want. But all told I would rather invest in good lenses than compromise so I'm open to suggestions.

Thank you!
Greg.

04-14-2011, 11:28 PM   #2
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for movement ... high speed movement.. i think you can use sigma 70-200/2,8 or DA 50-135 /2,8..its already HSM and i think the speed focus is enough for the martial speed..but ist not 300 usd

and for the fix lens you can use F 50/1,7 ... or sigma 50/1,4 ..its already HSM too ..
04-14-2011, 11:32 PM   #3
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The FA 50/1.4 does appear to be the best match for your selection criteria. As you say, you don't mind moving your feet, and you're just not going to get a fast sports zoom for that price.

Another option would be to upgrade the body to a Kx to get faster iso and therefore faster shutter speeds with your kit lenses.
04-15-2011, 01:11 AM   #4
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From my past experience and the fact, that your focus plane will be between 10-45' I would go for a f2.8 70-200 for tournament and large dojo action and a 50 f1.4 for smaller and darker action.

So for your budget give the 50mm a start.

04-15-2011, 01:49 AM   #5
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Sounds like you are right about the Tamron 28-75, if that focal length suits thens it's a great lens for you. I will eventually buy one for indoor family events to replace my Sigma 17-70 as I think it's a great range and f2.8 is very nice to have. Forget about convention wisdom, if in your experience 28-75 works then buy the Tamron.

By the way, forget about crop factor and conversions, just use your own zooms and experience to figure out what you need.
04-15-2011, 04:13 AM   #6
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I would also go with an F1.4 lens.

I have shot with my 50F1.4 and 105F2.8 and F2.8 was just too slow.

I never tried my 85F1.4 which may be just as good as the 50 and the extra length may be of use in some situations
04-15-2011, 04:59 AM   #7
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I'd buy that 28-70/2.8. And maybe buy a fast 50 with AF. You basically need a lens which is good with contrast wider lens is easy to shoot even wide open, but at tele end it takes more trying. It is also good to get known to all routines, that how your kid moves, so you could be in right spot and have her/his face at cameras direction there are some pauses between moves, that given nice time to shoot.
04-15-2011, 05:13 AM   #8
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Forget about the 'equals 42-112'. With the same calculation, your 50 equals 75. Again, forget about it.

I use FA31Ltd indoors at social events, so 28-75 not necessarily too long. Having said that, which focal length did you use with the 17-70 indoors? If you were mostly on 17 or 20, the 28-75 will not cut it.

I don't have experience with indoor action sports, so I can not advise from that perspective.

04-15-2011, 05:52 AM   #9
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Warning Math Involved!

one thing I missed in my official response is the suitability of focal length.

While there is a little math here, there is an easy way to get a rough idea of focal length range needed.

Basic optics determine that

Image Height = Subject Height *Focal length / Distance

First, an official sparring ring is 10 meters square, (33 feet for the metric impared) although amature (especially children) may be in smaller rings. But you need to consider that even at the endge of the ring, your shooting distance will probably be in the 5-10 meter range. If you are back further, this will also impact shooting distance.

If shooting children consider them to be 1-2 meters tall (maybe allow a little more for teens, who will have pretty incredible heights in jumping kicks)

Your image sensor is 24mm wide and 16mm high (in horizontal format)

so, if you want your subject at say 1.5 meters high fully in the frame, and you are sitting 5 meters away (ringside)

you can re-organize the formula

Focal length needed = Image Height * distance / Subject height

and plug in your numbers

you get focal length = .016 * 5 /1.5 = .053m or 53mm

this is why people who have shot TKD before have suggested a 50mm F1.4 lens. Nice and fast if you need the shutter speed and a pretty good focal length for the sport in an informal (amature) tournament.
04-15-2011, 08:29 AM   #10
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Well it depends on how close you can get and wich light there is. This picture was taken with DA 40mm/f2.8 Ltd pancake.

04-15-2011, 08:34 AM   #11
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Ron

is that the full frame or a crop?

with a 40mm, you would need to be inside the ring for a shot like that without cropping
04-15-2011, 08:54 AM   #12
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QuoteOriginally posted by Lowell Goudge Quote
Ron

is that the full frame or a crop?

with a 40mm, you would need to be inside the ring for a shot like that without cropping
top to bottom is compleet, picture taken in landscape and left and right took something of too make it square. I was allowed to stand in the corner, so if my pancakelens was longer it would be in the ring.
04-15-2011, 08:55 AM   #13
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I thought you were looking for a lens that knows Kung-FU !
04-15-2011, 09:16 AM   #14
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Ha well, if I throw this M-50mm hard it could do some damage. It would probably keep working too.

So I will consider the FA 50mm it seems like a handy lens to have in many situations and one I could keep for a long time to come. It's just not a lens I was looking forward to owning for some reason, though I don't have any particular reason for feeling that way. Maybe because I have the M-50 f/1.7 it feels like I'm giving up on it. Thanks for your help all.
04-15-2011, 10:47 AM   #15
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Ron

Based on your data that puts you about 3.75 meters or 12 feet away.

so from a little further back, or smaller contestants, a 50mm would do just fine.

for the OP, your manual focus 50 should be OK for this, I used my 50F1.4 for my son's
TKD from the edge of the ring. As long as he is not right on top of you, it should be fine
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