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09-28-2011, 03:31 AM   #1
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Unable to Focus on both foreground and background

Hi Guys,
I tried to bring the foreground and background together into focus but I succeeded to achieve only one at a time. With my little knowledge, I tried like increasing f- stop number(I used a tripod then). But no luck. I've used Pentax A 50mm f1.7, and a M 28mm f2.8 on my K-r. I'm just finding the bridge between the practical and theory. Also i've struggled to get a well lit photo against a bright landscape. I'd to use an external flash for this(pop-up flash is not enough). With point and shoot camera I could take these kind of pics very easily even with single hand. Please help me to overcome this with your inputs.
Best Regards,
Vass.
Note: I know few basics of SLR and I'm new to use it.

09-28-2011, 04:14 AM - 1 Like   #2
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You seem to know the theory - that a smaller aperture results in a greater depth of field. The DOF is a range of distances for which there is acceptable focus eihter side of the focus position at which the lens is set. If you are using typical new lenses (eg DA 18-55) the lens is intended for auto focus and does not have markings on it to assist manual focusing with awareness of the DOF.
Manual focus lenses do have such markings - so you can seen the band of distances which would be within the DOF for the aperture and focus setting. (Since the DOF is also a function of focal length it is more difficult to show this on a zoom.)
A focus technique you might usefully experiment with is to use these markings and set the lens so that the infinity focus settign is at one end of the DOF range for the apeture and then everyting to the other end of the band should be acceptably focused. The limitation of this method is that you need a lens with the DOF markings and points near to each end of the range will become progressively less sharp.
The approach to photography that I prefer is to acknowledge the finite DOF of a lens and get sharp focus on soem feature that you want to draw attention to in the frame and let the rest be OOF, as a deliberate aesthetic choice. That can be pleasing, and is why you will find many of the reviews on lenses making such a concentration on the bokeh property of the lens.
Now, with DSLR it is almost free to expose a frame, so I would recommend you go out often and take some pictures, and record what you did (EXIF data is a great help for that) and then view them as soon as you can afterwards on a computer, and critically appraise your pictures until you get a feeling for what works well. Start in good light, so shutter speed is normal, and once you get the basic technique right, then stretch yourself to try all kinds of daring things such as extreme open or closed apertures and extreme shutter speeds, including very slow.
Most lenses work best with middle apertures - at neither extreme of what the lens has available - the last stop at each end is likely to give slightly compromised pictures.
09-28-2011, 05:12 AM   #3
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Hi vass,

Regarding depth of field, tim60 really said it all, and you sound like you know that greater f-stop values (smaller apertures) gives you more depth of field. Of course it's true that shallow depth of field can be very pretty, but sometimes you just WANT the whole range in focus, and the right way to go about it is exactly as you say: Highest f-value and a tripod to compensate for the slower shutter speed.

To offer a totally non-technical point of view, if you want a person in the foreground and a landscape behind the person to both be in focus, picking your 50mm and stepping back will give you better results than picking your 28mm and stepping closer. If you have something even longer than 50mm, you can benefit from using this and stepping a bit further away. Also, in this example, be sure to focus on the person, not the landscape: You get a greater range in focus _behind_ your focus plane than in front of it.

So, if you pick your longest lens, pick the highest f-value, use a tripod and focus on the front object that you want to be in focus, you have done your best. Of course, if your shutter time is slow, the tripod will only keep your camera still and not your motive, so if there is a person in the picture you need to get them to stand still!

Your old point-and-shoot only had very small apertures available, so shallow depth of field was not an option - and therefore not something you had to think about. Now you get the choice of a wide or shallow DOF, so now you need to choose!

As for the dark foreground - bright background problem, you are actually BETTER off than with your point-and-shoot camera, because a dSLR is capable of capturing a greater range of shades between completely black and completely white. You just need to make sure that your metering (light measurement) is set to prioritise the area with your focus point, and again focus on the person in the foreground. If you experience worse results than you did with your p-and-s, then it's probably because that one automatically set the metering at the focus point, whereas now you need to TELL your camera that you do not want the exposure set for the whole scene. Once you set the exposure for the person in the foreground, you will see that the background gets more colour details and less pure white (burned out) areas than a shot from your p-and-s.

If you used fill-in flash with your p-and-s you can do this now also, but you should definitely be better off in this area now that you have a dSLR.

All in all, the problems come from having a wider range of choices, and once you get used to it, this also means more fun!

I hope this was helpful - good luck getting to know your new camera!

Mette
09-28-2011, 09:32 AM   #4
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QuoteOriginally posted by tim60 Quote
You seem to know the theory - that a smaller aperture results in a greater depth of field. The DOF is a range of distances for which there is acceptable focus eihter side of the focus position at which the lens is set. If you are using typical new lenses (eg DA 18-55) the lens is intended for auto focus and does not have markings on it to assist manual focusing with awareness of the DOF.
Manual focus lenses do have such markings - so you can seen the band of distances which would be within the DOF for the aperture and focus setting. (Since the DOF is also a function of focal length it is more difficult to show this on a zoom.)
A focus technique you might usefully experiment with is to use these markings and set the lens so that the infinity focus settign is at one end of the DOF range for the apeture and then everyting to the other end of the band should be acceptably focused. The limitation of this method is that you need a lens with the DOF markings and points near to each end of the range will become progressively less sharp.
Older Pentax lenses wider than 50mm are conveniently marked for this already. This is the Pentax-M 28mm f3.5, which should be pretty similar to the OP's 28/2.8. See the orange numbers on the distance scale and aperture ring? :



If you turned the focus and aperture rings so all the orange marks lined up, everything from about 5 feet to infinity would be reasonably sharp. If it is bright enough, f11 will increase depth of field. If your scene doesn't have a lot of distant detail, you can focus a little closer.

Wide-angle lenses are better for getting a lot of depth of field. You can compare the above distance scale to the one on the 50mm f1.7. If you set the 50mm to f8, you'd only get about 15 feet to infinity in focus:



09-28-2011, 01:25 PM   #5
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Just a small practical correction on Just1MoreDave's post above

Those DOF markings apply when those lenses are mounted on a full frame / film camera. As the Pentax dSLRs use a smaller sensor, you have to adjust by roughly one stop (basically 1.5, but 1.4 (one stop) is quite close). So if you have set your lens to f/4, you need to read / use the DOF markings for f/5.6 when using a Pentax dSLR

note: After reading riorico's post below it looks like I swapped the numbers around

You can use Online Depth of Field Calculator to calculate the depth of field and to see the effect of the aperture on the so-called hyperfocal distance. The hyperfocal distance is the focus distance the will give maximum depth of field for a given aperture.

examples (for 50mm lens on Pentax dSLR)
f/4. hyperfocal distance 31.3 meters, DOF from 15.65 meters to infinity
f/16, hyperfocal distance 7.86 meters, DOF from 3.93 meters to infinity

Last edited by sterretje; 09-28-2011 at 11:53 PM. Reason: Added note regarding swapped numbers
09-28-2011, 03:43 PM   #6
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I studied this website a LOT and it took me awhile but once I figured out the hyperfocal distance WHOA! The coolest thing is learning to TRUST the hyperfocal distance. It took me awhile to get over the fact that what I saw through the viewfinder was OOF but the photo is perfectly crisp. It was way cool
09-28-2011, 04:41 PM   #7
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The basic rules for DOF are:

For thicker DOF, use a shorter lens and/or a tighter aperture and/or a further subject.

For thinner DOF, use a longer lens and/or a wider aperture and/or a closer subject.

Those are the variables that control DOF: focal length, aperture, and subject distance. Modern lenses without aperture rings make hyperfocus-DOF work harder. And I don't expect much DOF in lenses longer than 40mm on APS-C unless they're stopped WAY down.

The basic way to hyperfocus an old manual lens on an APS-C dSLR is this:

* Decide on the DOF range you want -- what distance is to be in focus?
* Decide on the tightest aperture you want -- is diffraction a concern?
* Set the far distance on the lens scale to one+ stop LESS than the aperture.
. (So if the aperture is f/16, set the far distance mark to just inside the f/11 mark.)
* Decide if the near distance is acceptable -- if not, try a different aperture.

This gets a little easier if your far distance is infinity and you're using a fairly wide lens. IMHO 28mm isn't really wide, but let's swing with it. I decide to use f/16. I set the infinity mark to just inside the f/11 mark. I look at the other f/11 mark and see that it's at 1.2m / 4ft. So I know that my DOF is about 4ft to infinity. Maybe I don't want f/16; I'll try f/11. Set the infinity mark just inside f/8, look at the other f/8 mark: it's at about 1.8m / 6ft. So my DOF is about 6ft to infinity, maybe 7ft to infinity for best sharpness.

I can't get anywhere near that DOF with a 50mm lens. Let's say I stop it down to f/22. I set the infinity mark just inside the f/16 mark. The other f/16 mark is at 3m / 10ft. So 10ft to infinity is the absolute best DOF a 50mm lens can have. And I might start seeing diffraction effects at f/22. Bugger all; why does optics have to be so cruel?
09-28-2011, 10:14 PM   #8
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Test for pleasing picture

Many good responses.
When I got my dSLR I rapidly learned a rule: "when taking a picture of a person or animal, if the eye is sharp the picture will look OK, if the eye is OOF the picture will be unappealing."
If there is a choice between focusing on the person's eye and soemthing else - get the eye sharp.
Where possible, check the image captured immediately after capture on the camera screen, and zoom in on an eye. If you are still there you can take another chance. It took me a while to get used to checking images immediately, having learned with film.

09-29-2011, 04:00 AM   #9
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Hi Thanks to everybody for your valual inputs.I'll try to apply these inputs and hope i'll get better results.
@tim60
Thanks for the quick response and the nice tip, 'keep the focus on a persons eye'.

@MetteHHH
be sure to focus on the person, not the landscape: You get a greater range in focus _behind_ your focus plane than in front of it.Thanks for the tip. Here, I'm confusing whether to focus on FG or BG. Now it's cleared.Thanks a lot.
In the manual mode can I control the E+/E-(I don't know how to use this and when to use it) with the manual lens on K-r(Say Pentax M-50mm f1.4)? With Pentax A 50mm, I can only control Aperture and Shutter values in Manual mode.

@MoreDave
Thanks for the pictorial explanation. But to say frankly, I'm still confusing about the distances and how can I achieve the focus both FG and BG using this markings.I mean to say, the best we can get with this distance scale?

@sterretje
Again, :-s...sorry,unable use your valuable input as I couldn't understand the Online DOF Calculator, hyperfocal distance etc...Can you(somebody) please come down from your higher knowledge level of explanation..

@Hambino
I'm feeling jelous on you.How did you understand so easily the 'DOF Calculator'. The link you've given is really great and I yet to go through that fully. Thanks a lot.

@RioRico
Very explanation and I've learned 'Avoiding the both extreme values of the Aperture'.

Best regards,
Vass.
09-29-2011, 05:24 AM   #10
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QuoteOriginally posted by vass Quote
I've learned 'Avoiding the both extreme values of the Aperture'.
Actually the full range of aperture settings should be perfectly usable on any decent lens. While there is usually a falling off in sharpness at the ends, this is usually too small to worry about. However you probably won't want to use f/22 without a tripod except in very bright conditions. (For a great example of f/22, have a look at this shot of Jimbo's.)

Using a lens "wide open" (i.e., at the smallest f-number) is another matter. This gets you the thinnest DOF, which is sometimes just the effect you want to emphasize the subject, and also maximizes the lens's light-gathering power, allowing you to use a faster shutter speed. Your A 50 1.7 is a good portrait lens when used this way.

As to using fill flash on a bright day, try the 28mm lens and step closer to the subject. The effect of flash falls off quickly with increasing distance.
09-29-2011, 06:04 AM   #11
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QuoteOriginally posted by baro-nite Quote
Actually the full range of aperture settings should be perfectly usable on any decent lens. While there is usually a falling off in sharpness at the ends, this is usually too small to worry about. However you probably won't want to use f/22 without a tripod except in very bright conditions. (For a great example of f/22, have a look at this shot of Jimbo's.)

Using a lens "wide open" (i.e., at the smallest f-number) is another matter. This gets you the thinnest DOF, which is sometimes just the effect you want to emphasize the subject, and also maximizes the lens's light-gathering power, allowing you to use a faster shutter speed. Your A 50 1.7 is a good portrait lens when used this way.

As to using fill flash on a bright day, try the 28mm lens and step closer to the subject. The effect of flash falls off quickly with increasing distance.

This is for what I'm looking. This's what my requirement is. The grass infront of the water and the hills both are in focus. I appreciate the person behind the lens and thanks for the picture, which emphasizes my requirement more.

Sure. I'd have done it . Just I discovered something like i can increase the intensity of the flash by turning the E-Dial. So, realized that I didn't understand my camera a well enough. Have to explore..
Regards,
Vass.

Last edited by vass; 09-29-2011 at 06:06 AM. Reason: Mu comments embedded in baro-nite's quote.
09-29-2011, 07:17 AM   #12
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You're getting a lot more theory, and all the calculations to determine hyperfocal distance can be confusing and often inaccurate. It is harder to get the kind of foot-to-infinity clearity of a P&S simply because of sensor size. Here's some simple advice that works for me:
Always use a tripod. I'm a big fan of flash-fill, but not for scenic shots. It's much better to time your exposures for when the light is right (usually early and late in the day). Also shoot when there is no wind. Use the lowest ISO possible, center-weighted metering and AV mode for the desired f-stop and whatever shutter speed the camera selects. Use delay or remote for mirror-up function.
I've shot a lot of lenses over the past 40 years or so, and I've never found one that doesn't suffer undesirable diffraction at f-22. For what you want to do, your 28mm is best, because the wider the FL the wider the DOF, as Rio ponts out.
Set up and compose your shot. The sweet spot (or how high you can go on the f-stop number before suffering diffraction) varies with lenses. F-8 is a safe starting point. Expose a shot at f-8, then another at each apature setting above that (higher f-stop number) all the way to f-22.
Before each shot, twist the focus ring to infinity and very slowly bring it back until it just captures the foregound object you want in focus. Do it by eye, not by math. This way you are utilizing the maximum hyperfocal distance behind the foreground object for a given f-stop, instead of wasting any of it on the air in front of your foreground object. Refocus the way I described after each change in f-stop, because the hyperfocal distance doesn't just move away but toward you as well. It sort of expands from the middle, or maximum focal point, so if you simply change the f-stop without refocusing, you're only utilizing half the increase in DOF, while wasing the other half on dead air.
Examine these test shots full screen at 100 percent to compare them on your computer to determine the acceptable level of diffraction for that lens and your standards. This number is your standard for that lens for all-inclusive, yet sharp scenic shots. In brighter conditions, you can bump it up one f-stop. In duller conditions, it's best to drop it down one f-stop.
Get to know your lenses well. The body gets you there, but it is the eye (lens) that sees.

Last edited by Ron Kruger; 09-29-2011 at 07:25 AM. Reason: changed one worde
09-29-2011, 03:18 PM   #13
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Hi, Just gone through the DOF Master Hyperfocal Chart and gained a little knowledge on 'Hyperfocal distance'. Thanks to Hambino for posting the link. My doubt is, I'm using older lens on my Pentax K-r and I was told that I've to use a multiplication factor ,1.5(don't know exactly what's this, why to use and by what name it's called). So, say, my 50mm lens become 50*1.5=75mm. In this case which length should I consider? whether 50 or 75??
Regards,
Vass.
09-29-2011, 04:13 PM   #14
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QuoteOriginally posted by vass Quote
So, say, my 50mm lens become 50*1.5=75mm. In this case which length should I consider? whether 50 or 75??
Oh yes, lenses magically change their focal lengths when moved to different cameras. It's because of the faster-than-light neutrinos. I'm awaiting my Nobel for discovering this linkage.

Seriously: A 50mm lens is a 50mm lens no matter where it is. Different size frames (film or sensor) see different amounts of the projected image. That is, the CAMERA crops more or less of the image. The lens is totally innocent here. As baro-nite said, use the actual focal length in the hyperfocal calculator. Tell that to the SR'bot too.

Unless you're an experienced 35mm film photographer transitioning to APS-C, forget you ever heard of crap.factor. The format-faktor is useful when visualizing what AOV/FOV (angle/field of view) a lens will see on a different-size frame, and is otherwise confusing. And it doesn't even relate to DOF, which is a function of a frame's AREA, not its DIAGONAL. The 1.5x-factor is the ratio of the diagonals of FF and HF / APS-C frames. The ratio of their areas is 2x, which is why we adjust the on-lens DOF scale by 1 f-stop. I hope this isn't too confusing.

Last edited by RioRico; 10-01-2011 at 01:59 AM.
09-29-2011, 04:48 PM   #15
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QuoteOriginally posted by RioRico Quote
As baro-nite said ...
Heh. I guess I shouldn't have deleted that post. I decided it was slightly oversimplified and didn't want to elaborate. Anyway, as RioRico said ...
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