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03-21-2010, 06:18 AM   #16
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QuoteOriginally posted by RioRico Quote
Hi, Sung. For snap-ons, I don't know. I know that screw-on diopter sets were and are quite common, and can be easily found on eBay, often within mixed LOTS of miscellaneous gear. They're often just called CLOSE-UP LENSES. I usually see them in sets of three, of +1, +2 and +3 diopters. Let's see... a +2 on the kit lens at 55mm seems to have a working distance of around 2 feet / 61cm. And the +1 focuses out to 1.5-2m.

I suppose it COULD be possible to find a locate a 43mm-thread +1 diopter lens to screw into a snap-on Raynox universal adapter, bought separately -- but besides likely vignetting, the diopter lens would be a bit further from the primary than if it were screwed on. This would increase magnification somewhat and narrow the working distance. Maybe that would work for you. Maybe not.
Thanks, RioRico -- found a bunch on eBay and I just put a bid for one, so I can't wait to try it out. I couldn't find one with a +3, but I did get one with +1, +2, +4, and Macro. My guess is that +2 might be exactly what I'm looking for. I'm doing this for an extremely shallow DOF portrait...

- Sung

03-21-2010, 04:08 PM   #17
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QuoteOriginally posted by RioRico Quote
...Gosh. All these years in photography, and a bit of playing with diopter lenses for closeups, and I'd never bothered before to try them as portrait-mode DOF-bokeh machines. Duh! I'm sure glad the OP raised the question. So now we have a few ways to shrink DOF and increase background blur:

* Use a longer focal-length lens
* Set / use a bigger aperture
* Move subject further from background
* Move camera closer to subject
* Defocus / front focus a little
* Add slight extension to lens
* Use not-too-strong diopters

Can anyone think of any other tricks (other than PP)?
It's not within the context of bokeh, but a moving background works. I'm thinking of a subject in a city at night, probably lit by a flash, with traffic in the background.
03-21-2010, 04:33 PM   #18
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QuoteOriginally posted by sjwoo Quote
Thanks, RioRico -- found a bunch on eBay and I just put a bid for one, so I can't wait to try it out. I couldn't find one with a +3, but I did get one with +1, +2, +4, and Macro. My guess is that +2 might be exactly what I'm looking for. I'm doing this for an extremely shallow DOF portrait...
You checked to see that they'll fit your lens, I hope. I sometimes humiliate myself by accidentally buying a 49mm-thread filter for a 52mm-thread lens. Duh. And yes, a +2 has a dramatic effect. Have fun!

QuoteOriginally posted by Just1MoreDave Quote
It's not within the context of bokeh, but a moving background works. I'm thinking of a subject in a city at night, probably lit by a flash, with traffic in the background.
That's good, especially with slow-speed sync or trailing shutter sync. (NOTE: The K20D manual says to switch SR off and use a tripod for trailing shutter sync.) That trick, which I didn't mention since it's not precisely about DOF, ensures the subject is much better lit than the background. It's also fun for both shooter and subject to be on a merry-go-round, in a moving vehicle, etc -- as long as you're both strapped down! And to use a slow shutter with moving water or machinery as a (safely distant) backdrop.
03-23-2010, 07:01 AM   #19
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QuoteOriginally posted by RioRico Quote
I decided to experiment a little, with the FA 50/1.4, whose close focus is 5.5 inches / 135mm. I put a +1 diopter on the wide-open 50 and focused at a target about 1.5m away, a reasonable close portrait distance. Background blur (bokeh) increased slightly but noticeably. Then I tried a +2 diopter. Close focus distance dropped to under 1m and the bokeh softened dramatically. For *close* portraits, this cuts DOF about as thin as you'd want to go. Don't slice off your fingers!

* Defocus / front focus a little
* Add slight extension to lens
* Use not-too-strong diopters
1 Can you explain more about this how this affect the dof?
- front focus a litte
if taking a portrait where would you focus?
2 add slight ext to lens
- dont really understand this
3use not too strong dipoters
how can adjusting the diopter affect the dof?
Thx

03-23-2010, 07:40 AM   #20
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QuoteOriginally posted by rustynail925 Quote
1 Can you explain more about this how this affect the dof?
- front focus a litte
if taking a portrait where would you focus?
2 add slight ext to lens
- dont really understand this
3use not too strong dipoters
how can adjusting the diopter affect the dof?
Thx
Front-focus: focus a little in front of the subject. For instance, if you're shooting a portrait, have the subject hold their hand in front of their face. Focus on that. Then move hand away, and shoot. Your goal is to have the front of the face sharp enough, and everything else fuzzy enough, to make the face stand out.

Slight extension: I'll put a screwmount 35mm or 50mm lens on a flanged adapter, which is about 1mm thick. Or I'll put a 135mm or 180mm lens on the shortest possible macro tube, about 12mm. Now the lens will no longer focus to infinity -- but I don't WANT infinity, I WANT what's behind the subject to be fuzzy. The extension brings the working distance down, makes me shoot closer, and shrinks the DOF. If I use SR, I add that extension to the focal length -- so with a 135mm lens and 12mm extension, I tell SR that the focal length is 150mm. (Close enough!) And that 135 lens, which used to focus 1.5m to infinity, now focuses about 1m to 2.5m, good for portraits.

Diopter lens: I don't mean the diopter adjustment on the camera's viewfinder. There are close-up or diopter lenses, often sold (cheap!) in sets of +1, +2, +3 or 4, that you can screw onto the front of any lens like a filter. These act as magnifiers. They force you to shoot closer, and they shrink the DOF. On a kit lens, +3 or stronger make you get mere inches from the subject -- good when shooting snails, not so good for people. On a kit lens at 55mm, with the lens focused to infinity, a +1 diopter gives a working distance of about 1.5m to 2m; a +2 diopter works at about 0.6m. The subject at that distance is sharp, everything further is fuzzy.

EDIT/CORRECTION: About extensions -- using a 135mm lens with 12mm extension would work with a 35mm FF film camera, but not with our dSLRs. It's better to use a 180 or 200 or 240mm lens, otherwise too much of the APS-C frame is filled with too much of a face.

Also note that when shooting with very thin DOF for portrait work (especially feminine), a tack-sharp *LTD lens with precise AF may not be best, or even desirable. Such portraiture favors softness. Pentax even made a (rare) 85mm f/2.8 Soft portrait lens. Anyone without the time and money to acquire that baby can play DOF tricks with cheap lenses wide-open.

Last edited by RioRico; 03-23-2010 at 08:44 AM. Reason: correction
03-25-2010, 07:37 PM   #21
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Thanks all for the responses! It seems that in order to get bokeh out of the kit lens without any other accessories, I'd need to be amazingly close to the subject....

For this reason, Im thinking of going the two lens route: one wide or ultra wide (perhaps a Sigma 10-20) and one portrait (50 1.4), instead of the kit lens..
03-26-2010, 11:26 AM   #22
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Being very close to your subject is one way to get shallow DOF. But simply having a background that is much further away than your subject is another.

I think you'd be making a huge mistake not getting the kit lens in favor of lenses are either much shorter or much longer than "normal". There's more to like than shallow DOF, and much of that life is best captured with somewhere around a "normal" FOV (28-40, say). by all means, get a wide angle and a fast prime lens too for the situations that require it, but if you're not already such an expert in photogrpahy that you know for absolutely sure that you'd be in the tiny minority of photographers who doesn't use the '"normal" rnage much, I think you need to assume you'd be like the vast majority who do.
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