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11-01-2015, 08:04 PM   #1
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Focal Length Analysis from Recent Event / Lens Choice Optimization

A few weeks ago I photographed a Walk-a-Thon fund raising event at my kid's elementary/primary school. I shot 584 images with my K-3 with a DA 18-135mm lens. From this collection of images, 37 were erased prior to loading into Capture One for processing which left me with a grand total of 547. This number was further whittled down to 158. Based on an initial count of 584, my keeper rate is a lowly 27%.

A very small percentage were sharp but poorly composed (i.e. cropped off heads during pans, way too crooked horizons, etc). Most of the rejected images were cast aside because they were soft and out of focus. In a previous thread, I learned that my poor technique may have played a larger part in this low keeper count. My AF function was linked to my shutter button being pressed half way and I was using a AF single point. I also didn't engage burst mode. Using the rear AF button with multiple AF points and a burst mode may have resulted in a higher keeper count. Getting 258 images from 684 total shots would have been awesome! I understand this dynamic and I am practicing this "new to me" technique with my DA 18-135mm. The body/lens combo can certainly be made to focus more often. Anyone who looks at my Flickr account can tell I am mostly a static portrait enthusiast.

In parallel to improving my technique, I am questioning if my DA 18-135mm is a well suited lens for action photography in general. With a focal length ratio starting at f/3.5 that only gets larger as I zoom in, I think that the wide-open depth of field may be too big and the AF-C may not be triggered as much as if I were using a faster, constant wide-open aperture lens with a shallower depth of field. If I do purchase a new, faster lens then I want to know which one to get. A 17-50mm? A 28-75mm? What about a 70-200mm? I created a histogram of the focal lengths I used during the event. Each individual focal length as reported by Capture One is an individual bar below :



Is there a way that I ought to group the data for better presentation?

Shown as-is, I see the majority of my photographs lie between 28mm and 78mm. A lens like the DA 16-85mm would provide a very useful focal range for me in this situation. It would capture the majority of my shots and have a little extra zoom range to capture most of my extremes. However, I don't think it offers me enough to abandon my DA 18-135mm because it's not any faster of a lens. So where does that leave me? Tamron has the 28-75mm f/2.8 but it lacks the wide angle view of 18-28mm. Sigma has a 17-50mm f/2.8 but it lacks on the tele end. The 17-70mm from Sigma seems like a good choice but it is variable aperture. Perhaps the 17-70mm is the best lens on paper for what I do but I wonder about that variable aperture. There is no single f/2.8 lens that does it all.

I wonder if this means I would be better suited to carrying two bodies, each with their own lens, for different purposes. Could I mount a fast focusing f/2.8 lens on my K-3 and use a slower, broader lens on my u4/3 body? The K-3 would be great for tracking action whereas the u4/3 body would be good for static or slow moving shots.

I'd like to hear from my fellow forum members on how they would approach this shooting scenario. Would you simply give up some shots to get other shots? Would you go for a two body/lens system? Am I starting to cross over into equipment that would require me selling my internal organs oversea to fund new purchases at home?

11-01-2015, 08:20 PM   #2
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That's a very specific event profile - is it representative of your use of the lens? If so I would think that 28-75 f/2.8 might work well for you but the new 24-70 might be even better - crazy money by comparison however. I'd give the 18-135 another go with the change in settings before I would conclude much about it.
11-01-2015, 10:00 PM   #3
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do some focus tests on your lens, mine need ed quite a bit of adjustment.
11-01-2015, 10:48 PM   #4
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I shoot a lot of motor bike racing. Motocross on a super cross type track, tight track with big jumps, and what we call grass track or natural terrain motocross, big track, large area. For those, I use a Sigma 70-200mm F2.8 and a 24-70mm F2.8 on another camera. Setting AF-C and centre focus point. The tight tracks mainly use the 24-70 because the bikes a close. On the open track I mainly use the 70-200, because I'm not as close to the rider's/bikes. I do have access to the tracks, but I don't want to get too close if I don't have too. On the tight tracks I have no choice, there's not much room to move. So a short lens is fine.

I think for what you photographed your lens is about right. But it depends on how close you can get, or want to get to what your shooting. To what's the best lens. Fast moving subjects might require a faster focusing lens. Or changing your settings. AF-C and centre focus point, faster shutter speeds and panning with the subject as it move's past/towards you. it's easier to keep subjects in focus when they move past as apposed to moving towards/straight at you.

As UncleVanya said, I would give the 18-135 another go with a change in settings/technique. Maybe try catch in focus shutter release, and/or increasing your shutter speed.

If you know you can get close, a shorter lens is fine. But sometimes you may need that extra reach. That's where the longer end matters. Or you go with the two camera setup. One long lens and one short lens. Knowing what you'll use that lens for is the thing. If there's no problem getting close when your shooting your subject. Use a shorter lens and just get closer. Your legs can make a great zoom at times..

11-01-2015, 11:51 PM   #5
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QuoteOriginally posted by 6BQ5 Quote
A few weeks ago I photographed a Walk-a-Thon fund raising event at my kid's elementary/primary school. I shot 584 images with my K-3 with a DA 18-135mm lens. From this collection of images, 37 were erased prior to loading into Capture One for processing which left me with a grand total of 547. This number was further whittled down to 158. Based on an initial count of 584, my keeper rate is a lowly 27%.

A very small percentage were sharp but poorly composed (i.e. cropped off heads during pans, way too crooked horizons, etc). Most of the rejected images were cast aside because they were soft and out of focus. In a previous thread, I learned that my poor technique may have played a larger part in this low keeper count. My AF function was linked to my shutter button being pressed half way and I was using a AF single point. I also didn't engage burst mode. Using the rear AF button with multiple AF points and a burst mode may have resulted in a higher keeper count. Getting 258 images from 684 total shots would have been awesome! I understand this dynamic and I am practicing this "new to me" technique with my DA 18-135mm. The body/lens combo can certainly be made to focus more often. Anyone who looks at my Flickr account can tell I am mostly a static portrait enthusiast.

In parallel to improving my technique, I am questioning if my DA 18-135mm is a well suited lens for action photography in general. With a focal length ratio starting at f/3.5 that only gets larger as I zoom in, I think that the wide-open depth of field may be too big and the AF-C may not be triggered as much as if I were using a faster, constant wide-open aperture lens with a shallower depth of field. If I do purchase a new, faster lens then I want to know which one to get. A 17-50mm? A 28-75mm? What about a 70-200mm? I created a histogram of the focal lengths I used during the event. Each individual focal length as reported by Capture One is an individual bar below :



Is there a way that I ought to group the data for better presentation?

Shown as-is, I see the majority of my photographs lie between 28mm and 78mm. A lens like the DA 16-85mm would provide a very useful focal range for me in this situation. It would capture the majority of my shots and have a little extra zoom range to capture most of my extremes. However, I don't think it offers me enough to abandon my DA 18-135mm because it's not any faster of a lens. So where does that leave me? Tamron has the 28-75mm f/2.8 but it lacks the wide angle view of 18-28mm. Sigma has a 17-50mm f/2.8 but it lacks on the tele end. The 17-70mm from Sigma seems like a good choice but it is variable aperture. Perhaps the 17-70mm is the best lens on paper for what I do but I wonder about that variable aperture. There is no single f/2.8 lens that does it all.

I wonder if this means I would be better suited to carrying two bodies, each with their own lens, for different purposes. Could I mount a fast focusing f/2.8 lens on my K-3 and use a slower, broader lens on my u4/3 body? The K-3 would be great for tracking action whereas the u4/3 body would be good for static or slow moving shots.

I'd like to hear from my fellow forum members on how they would approach this shooting scenario. Would you simply give up some shots to get other shots? Would you go for a two body/lens system? Am I starting to cross over into equipment that would require me selling my internal organs oversea to fund new purchases at home?
Pretty interesting!

At least two times the year I shoot Taekwondo events in sports halls and did a similar analysis 3 years ago. I use my K5 with 18-135 and get nearly the same amount of images with similar spread of focal lengths at each event. In my opinion a focal length of 18 - 135 is really perfect for the events because I don't need to change lenses.

After I had analyzed the images I changed my technic as follows:
single shots using AF.S, Tav (T= mostly 1/125, A = f4.5/5.6 - f7.1), adjust focal length, prefocus with autofocus (center point), recompose and using quick shift to adjust focus if necessary.

Depending on the situation I change time and aperture slightly. I think the keeper rate is better today. 50% of the images are at least ok images I think.

But I also would like to get some images with less depth of field.

Because of that I'm thinking about buying the f2.8/24-70 plus using something like a f2.8/50-135 with second body. I'd really like to see a second version of the 50-135 with reliable and fast autofocus, ...

Last edited by acoufap; 11-02-2015 at 01:50 AM.
11-02-2015, 12:46 AM   #6
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Its a shame you don't do the analysis on the whole set and the keepers.

It would be useful to know what didn't work, not just what did.

Just looking at this, my tamron 28-75 would capture 90% and the 16-85 I bought my daughter would be a little better, plus for the ones over 85mm you can always crop a little.

From the middle of the graph, you certainly don't need the 18-135. The questions will always carter around what shots you like the best. You realistically can't cover everything with one lens. But is there something you perhaps miss at either end of the range, that's why it is interesting to see what you didn't keep.
11-02-2015, 04:44 AM   #7
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For AF tracking, a f2.8 lens helps. If I compare the DA300 f4 and Tamron 70-200 f2.8 lenses in AFC tracking, the number of in focus shot with the 70-200 screw drive is twice as much as with the DA300. The reason is not the speed of AF motor, the reason why the DA300 is less often in focus is because the AF module is not able to distinguish distant planes of focus as well as the f2.8. So, you would NOT go for a DA16-85. A 50 f1.4, 70 f2.4 , 24-70 f2.8, 70-200 f2.8 would serve you better for AFC tracking. The other thing is the AF hold setting that can be selected on the K-3. The more hold you select, the less sensitive it is to subject background but is also less sensitive for tracking in the Z direction, that means there is a tradeoff to be decided depending if tracking in Z or XY. When tracking in Z axis (aligned with lens axis), AF holding #1 is more reactive (closer tracking). When tracking in the XY plan (perpendicular to lens axis), AF hold #3 is better, and AF hold #4 is very sticky but less sensitive.

Last edited by biz-engineer; 11-02-2015 at 02:56 PM.
11-02-2015, 05:04 AM   #8
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This is one of the reasons I rejected the 16-85 as my go-to lens for all damp-weather work; no faster across the board, and I need the top 50mm more than I need an extra 2mm at the wide end. Lowell Goudge is right - you should have run the curve on all the pics you took. This is also the reason why I keep almost all my shots - except for the ones where I obviously fudged the settings or forgot to pop up/turn on the flash or something stupid like that, and ended up with either complete dark or total blow-out.

The data, by the way, are very clearly presented.

Going for the 28-75 would have lost you eleven of your keepers at the wide end and (theoretically) 27 at the tele end (assuming you weren't willing to crop to get them). The question we'll never be able to answer, of course, is how many more it would have got you in the middle.

Your theoretical perfect setup is two bodies, 16-50 and 50-135, both of which give you f/2.8 across the board. But oh, the price... and that's before we get into the thorny issue of how much you can trust the SDM lenses (provided you haven't already converted them to screwdrive) and the physical encumbrance of carrying both.

11-02-2015, 06:50 AM   #9
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QuoteOriginally posted by biz-engineer Quote
For AF tracking, a f2.8 lens helps The reason is not the speed of AF motor, the reason why the DA300 is less often in focus is because the AF module is not able to distinguish distant planes of focus as well as the f2.8. So, you would go for a DA16-85. A 50 f1.4, 70 f2.4 , 24-70 f2.8, 70-200 f2.8 would serve you better for AFC tracking.
Did you mean 16-50?
11-02-2015, 07:13 AM   #10
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Your next lens would depend on what happens to your pictures after you take and distribute them. If they are going to go on the interwebs, you could use a fast lens like Pentax 16-50mm f2.8 or the Sigma 17-50mm f2.8 and simply crop the needed portion - the 24MP should give you enough room to play with substituting the longer focal lengths.

If you are going to print then yeah, you would do better with the two lenses (16/17 - 50 and 50-135/150).

I shoot indoor roller derby with Sigma 50-150mm f2.8 and have been pretty happy with the pictures. For some situations I wish it were wider (when the skaters are close to me) but I try to anticipate and step back in time...better than carrying two cameras. I really need the 150mm end when they are at the far end, and the f2.8 for low indoor lighting. I always use center-point focusing (since I don't want the camera to automatically pick up focus on the opposing team's skater at f2.8) and pick the right subject using the back-focus AF button (so the shutter button is de-linked from focusing). Pretty content with this setup.

All that said, since your walk-a-thon is outdoors, the 18-135mm seems like a great focal range and you probably don't need apertures wider than what the 18-135 has for lighting purposes. Try center-focus (not multi-point) and take time to focus on the right subject rather than let the camera decide where to focus. Lesser shots that deliberately focus on your 'correct' subject (and therefore a higher keeper rate) is better than a higher number of shots with a lower keeper rate where focus on the 'correct' subject is by chance, IMO. As UncleVanya said, give that lens one more go.
11-02-2015, 07:59 AM   #11
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You could could continue to use a zoom, but if you crop, it looks as though an SFL lens of 30 to 40mm would capture a huge percentage of the images. A Pentax 40mm f2.8, which can be had used at very attractive prices, especially the original version, might serve you well. It has excellent IQ and could probably survive rather severe cropping and still deliver good sharpness.

Last edited by WPRESTO; 11-02-2015 at 04:01 PM.
11-02-2015, 02:57 PM   #12
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QuoteOriginally posted by UncleVanya Quote
Did you mean 16-50?
I corrected my writings...
11-02-2015, 03:06 PM   #13
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QuoteOriginally posted by biz-engineer Quote
For AF tracking, a f2.8 lens helps. If I compare the DA300 f4 and Tamron 70-200 f2.8 lenses in AFC tracking, the number of in focus shot with the 70-200 screw drive is twice as much as with the DA300. The reason is not the speed of AF motor, the reason why the DA300 is less often in focus is because the AF module is not able to distinguish distant planes of focus as well as the f2.8. So, you would NOT go for a DA16-85. A 50 f1.4, 70 f2.4 , 24-70 f2.8, 70-200 f2.8 would serve you better for AFC tracking. The other thing is the AF hold setting that can be selected on the K-3. The more hold you select, the less sensitive it is to subject background but is also less sensitive for tracking in the Z direction, that means there is a tradeoff to be decided depending if tracking in Z or XY. When tracking in Z axis (aligned with lens axis), AF holding #1 is more reactive (closer tracking). When tracking in the XY plan (perpendicular to lens axis), AF hold #3 is better, and AF hold #4 is very sticky but less sensitive.
You need to consider what the OP is doing, I don't disagree that for distant shots a 200/2.8 will give better separation that an300/4 (maybe, ) but we are discussions the difference between 50 and 85mm and shooting close in. Also given the range of focal lengths the use of primes while giving better separation is wholly impractical with a single body at a sporting event needing range of 16-85'm. A zoom is warranted here, and since DOF is inversely proportional to focal length you don't need as fast at the long end for the same DOF
11-03-2015, 01:16 PM   #14
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From the graph I think that a 28-75 or 24-70 would cover almost everything. I would go for the sigma 24-70 f/2.8, I think this is great lense for tracking better than a 16-50, the 24mm still allow for moderate WA and for many events and people you don't need to be wider than often and could still out the 18-135 from the bag for theses cases without having to switch too much. This is great solution for 1 lens setup because 50mm is really too short and that 17-18mm is not that needed.

Sure 16-50 + 50-135 would be much better but you spend more money, you need to swap lenses or bring in 2 cameras and even you need to swap cameras so you'll miss more shoots than if you are 100% ready with 1 lense.
11-03-2015, 01:31 PM   #15
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You rarely go UW or longer tele. There are several lenses in the 24 or 28 to 75 category which are much better than what you have - f2.8.

Keep a couple of primes in the bag or car for wider or longer, but truth be told, you could probably do without them altogether, according to that distribution.

My own would probably have two humps ... the shots are either very wide or closeups, not much in between.
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