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08-19-2010, 07:44 AM   #1
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Bokeh walking down the street and other problems.

Hi all,

I have a Pentax k-x with the 18-55mm kit lens and am thinking of upgrading my lens.

What I'm interested in shooting are people walking down the street or in action poses and sports(soccer players mainly).

I was initially going to spend money on an 18-200mm sigma lens because I couldn't get the depth I needed without walking right up to what I was trying to focus on but then I read up some more and it seems I may be mistaken.

I want to shoot pictures of someone (my gf) walking down the street with just her in focus while the background and foreground or blurry (bokeh as I recently found out).

Would the 18-200mm lens be appropriate or would I be better served with a 50mm f1.4 or f1.7mm lens instead?

Would the 18-200mm be useful for cityscapes or would the 50mm lens be useful for that as well?

Thanks in advance.

theteerex

08-19-2010, 08:03 AM   #2
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You'll actually want something long but with a large aperture, such as the sigma 70-200mm f2.8. Please check the lens reviews for details on that lens

It should be able to generate the smooth bokeh you're looking for!
08-19-2010, 08:05 AM   #3
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Just to clarify, the blurriness of the background is due to it being out of the focal plane. The quality of the rendering of that out of focus area is bokeh.
08-19-2010, 08:12 AM   #4
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A 50mm 1.4 or 1.7 should do the trick for you - subject isolation with decent borkeh - if you shoot wide open, or close to it. Pick up a SMC A 50 1.7 from eBay for a few bucks and give it a try. It's a useful portrait focal length on crop.

08-19-2010, 08:13 AM   #5
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Bokeh will be a function of focal length and speed of lens. In terms of portraits, a fast 50 will give you nice bokeh, but so will a 300mm f4. The question is how close to you want to get for your portraits?

The most versatile portrait lens for Pentax is the DA 50-135 f2.8, but that's an expensive lens. The FA 77 would also make an excellent portrait lens, but again, it's pricey.

QuoteOriginally posted by theteerex Quote
Would the 18-200mm be useful for cityscapes or would the 50mm lens be useful for that as well?
By "cityscapes" I suppose you mean wide angle shots, in which case, a 50mm lens would probably be too tight. What you could do is go out and shoot some cityscapes with your 18-55 mm lens and see what focal lengths best serve your needs.

While the 18-200 would be a versatile lens, it is so at a price. At 18mm, there's probably going to be serious barrel distortion, which may be an issue with photographing buildings, and at the long end of the lens you may have issues with lack of contrast and sharpness.

If you're looking for an economical one lens solution and are willing to go manual focus, the old Pentax A 35-105 f 3.5 might fit your needs, assuming that 35mm is wide enough for cityscapes. The lens is sharp and capable of very pleasing bokeh (though, for portraits, you may need to shoot it at 105mm to get what you want). Otherwise, I would be inclined to go with a fast 50 and use your kit lens for cityscapes until you can afford something better.
08-19-2010, 08:45 AM   #6
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QuoteOriginally posted by theteerex Quote
I have a Pentax k-x with the 18-55mm kit lens and am thinking of upgrading my lens.What I'm interested in shooting are people walking down the street or in action poses and sports(soccer players mainly).
Some here will argue that instead of "upgrading", you should "supplement" the kit lens. Whatever. You know what you need for longer reach -- a longer lens. If you don't mind switching views at around 55mm, a 50-200 or 55-300 would do. If you don't like switching there, an 18-200 or 18-250 (what I use) is comfortable. I've tried an 18-55 and 60-300 pair and I just don't like switching there.

QuoteQuote:
I want to shoot pictures of someone (my gf) walking down the street with just her in focus while the background and foreground or blurry (bokeh as I recently found out). Would the 18-200mm lens be appropriate or would I be better served with a 50mm f1.4 or f1.7mm lens instead?
Now it gets complicated. What you want, with a sharp subject and everything else blurred, is thin DOF (depth-of-field). Various methods will achieve that. The cheapest is to add a +1 diopter lens, but that only works with a nearby subject. Or, buy a very fast lens and use it wide-open. Or, buy a longer lens and shoot from a distance. I can fill a frame with a headshot with a wide-open 50/1.4 (many bucks). I can also fill a frame with a headshot with a wide-open 135/2.8 (ten bucks) from a greater distance. DOF will be about the same.

Some tricks here: If using an AF lens, set your Program Line to Hi-Speed Priority; this keeps the aperture open as much as possible when in Green or P modes, for thinner DOF. Keep your subject away from a background; the further away the background, the blurrier it will be. Keep the camera as close to the subject as possible; again, this blurs the background. If shaded, use a fill flash; this lights the subject while the darker background fades away.

QuoteQuote:
Would the 18-200mm be useful for cityscapes or would the 50mm lens be useful for that as well?
Yes. I use my 18-250 for land-, city-, ocean-, village-, and mountain-scapes. I also use 24-28-35-50-58-85-100-200mm lenses for such scapes. And a Fast Fifty is useful in many situations. AF or manual, new or old, it doesn't matter. My original lens set for my K20D were the DA10-17, DA18-250, and FA50/1.4. I sometimes replace the 10-17 with a Zenitar 16/2.8 (US$170), and the FA50 (US$200 then, $350 now) with an A50/1.7 (US$50) or ST55/1.8 (US$9 then, $30 now).

Good luck!
08-19-2010, 08:50 AM   #7
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How does b(r)okeh compare from 50 mm F1.4 to for example 100 mm F2.8?
- I thought longer with same F number was better for "blur"
- Of course you also need to make the distance to object twice as large (can become impractical...)


FYI: I want to buy K-x with 18+55 kit lens + DA*50-135 mm F2.8 lens and I am also wondering if I should add a 50 mm F1.4 for portraits or rather go for something shorter to more general low light photography (e.g. 30 mm F1.4 or 40 mm pancake).
08-19-2010, 09:09 AM   #8
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Thanks for the replies.

Just to clarify, I want a full body shot of someone walking down the sidewalk and focus while both the foreground and background have good bokeh.

If I don't want to be close to the person, I should be able to get the effect at say 5 meters away with a sigma 70-300mm F4-5.6 APO DG Macro or sigma 18-200mm F3.5-6.3 DC?

Or use a 50mm f1.7 pentax but stay a bit closer like 1 to 2 meters away?

I desperately want to stay below $400 as money is tight.

Thanks.

08-19-2010, 09:26 AM   #9
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How much does the Sigma 50 mm F1.4 or Pentax FA 50 mm F1.4 cost?
- I thought the Sigma was < 500 (sorry) and Pentax actually < 400, but not sure if I am thinking in Euro's or USD...

Maybe also interesting to read:

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/109830-best-po...ml#post1148576
08-19-2010, 10:28 AM   #10
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QuoteOriginally posted by JoepLX3 Quote
How much does the Sigma 50 mm F1.4 or Pentax FA 50 mm F1.4 cost?
- I thought the Sigma was < 500 (sorry) and Pentax actually < 400, but not sure if I am thinking in Euro's or USD...
About $379 so right up there. The one the moderator suggested had a retail price of $2400 on the sigma site. I'm sure cheaper somewhere else but not by so much that it becomes <$400.
08-19-2010, 11:11 AM - 1 Like   #11
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QuoteOriginally posted by JoepLX3 Quote
How does b(r)okeh compare from 50 mm F1.4 to for example 100 mm F2.8?
- I thought longer with same F number was better for "blur"
QuoteOriginally posted by theteerex Quote
Just to clarify, I want a full body shot of someone walking down the sidewalk and focus while both the foreground and background have good bokeh.
...I desperately want to stay below $400 as money is tight.
Don't confuse bokeh with blur. Blur can come from camera or subject movement (oops) or from controlling the DOF via aperture and distance. Bokeh is the *quality* of the blur, according to your (or your clients') tastes, and the needs of an image. I'd argue that while you'd want smooth, creamy bokeh to offset a sharp, detailed subject, so you might want a jagged, ugly bokeh to offset a smooth, bland subject.

The goal is to highlight the subject, to make them distinct from what's around them. How? Controlling OOF (out of focus) blur is pretty straightforward: wider aperture, and/or longer focal length, and/or more separation of subject from surroundings. A portrait or tele lens (in the 50-200mm range) acts like a knife, slicing the subject out of their visual matrix. So does a well-used ultra-wide lens, by shrinking the background into insignificance. And so does the right lighting -- illuminate the subject, keep everything else dark.

How to do this cheap? Go manual. Good manual zooms in the 70-210/4 area can be had for well under US$50. I'm still seeing 50-55's f/1.7-2 selling for under US$20. Get some undervalued Sears or Vivitar glass (CHEAP!) and see if those focal lengths and speeds give the effects you want; this could help you decide whether to spend more money on new AF lenses. Good luck!
08-19-2010, 11:32 AM   #12
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In that case, I'm going back to the store I was just at and picking up the manual 50mm f2 the owner had for $45!!!
I'll post the results later.
08-19-2010, 11:49 AM   #13
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One really big point I haven't seen mentioned (might have missed it) is focusing distance. This has a major effect on depth of field with any speed or focal length lens.
08-19-2010, 01:16 PM   #14
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Here are some shots i made today with my SMC Pentax-M 50mm F1:1.2 lens (i just bought it today)

The shots are taken with F1.2, F2.0, F2.8 and F4.0
You can see that wide open at F1.2 there is a extremely shallow DOF, while at F4.0 the DOF is much larger.
I didn't use any PP

I know the 50mm F1:1.2 is rather expensive, but the same story for DOF goes for the Pentax-M 50mm F1:1.7 that can be found for $50.- or so.
It is really worth the try.








Last edited by Sakura; 08-19-2010 at 01:24 PM.
08-19-2010, 02:16 PM   #15
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You already received some good advice. Let me add that your original lens option (18-200mm or 50mm) might not be the best. The Sigma 18-200mm is an older lens; a better choice would be the Tamron/Pentax 18-250mm that is considered a better package than the kit lens (see lens reviews in the Forum database).

I think that some good prime lens (eg 50mm) may give you some better bokeh than a zoom lens, and there are many good primes for Pentax mount. A zoom lens need to be a compromise over the focal distance range *eg 18 to 250mm) and it cannot be optmised like a prime lens.

Hope that the comments will assist.
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