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06-30-2010, 07:11 PM   #16
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as already stated the dof is 1 inch if you where not using a trypod and your young subject was not perfactly still this is type image you will get. so untill lensego sayes he was on a trypod and his rather young and energetic subject was perfectly still and that that is the same with the 30% hes loosing this is most likly user error that is extremely common with this lens and a new user to it.

06-30-2010, 07:55 PM   #17
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Caught myself out for a while when I first went digital, the camera was doing things OK, but not where I wanted.
Sounds obvious, but make sure that the eyepiece diopter is focused too, or you might think you are auto focusing sharp on the right point but you are not.

Easy to do, just push the shutter button halfway down and look at the figures along the bottom in the eyepiece, focus the diopter till they are sharp, job done.
Can do with the lens cap on, probably better as you are not disctracted by what appears via the lens.
06-30-2010, 08:56 PM - 1 Like   #18
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QuoteOriginally posted by lensego Quote
Attachment 65314
Hi guys. What em I doing wrong? I'm getting at least 30% of my pics like that:
Center of the picture is not sharp . I used Fa 50/1.4 at wide open. I'm loosing lots of pics that way. I understand the DOF is very short at 1.4, but why is that lens focusing behind my little beautiful sobject? Lots of funny sad etc faces are gone by that mistake
ps: If it is not obvious :the face is out of focus, but the jumper around the neck is sharp.
Any help would be great
Hi Zoltan,

First of all, the very center of the pic is actually sharp. Look at the line of the side of the child's face in the very center. This focus plane would be just in front of the ear, and too far back to get good forcus at the eyes. if you superimpose an imaginary focusing screen grid over the pic, I think you'll see what I mean. the fact that part of the collar is in focus is probably just coincidental, since it's the same distance as the side of the face. The camera probably didn't focus on it. . .

I'm making a couple of assumptions. I'm assuming that you used center point focusing or select point with the center point selected, and I'm assuming that you either used AF or trusted the AF sensor to indicate proper focus. Even if these are not the case, what I have to say might still help.

With lenses that have very thin Depth of Field, as this one does wide open, you need to know how the focusing system works -- not just "press the shutter button half way and it focuses", but rather how big the focus sensor area is, where it's located, and what it's "looking" for, and to an extent, how it works. I will not state that this is definitive explanation of how the Pentax system works it's just some conclusions from some significant use, but I think it's pretty close. . .

1. The center AF sensor is approximately the size of the central ( ) circular area etched in the viewfinder.

2. The center AF sensor is the largest of the 11 in the SAFOX AF system. It is shaped like a "+" The surrounding eight focus sensor points are also cross-shaped, but more shaped like a "T" with the tail pointed in the general direction of the center of the frame, and are a bit smaller. The two outermost sensors are shaped like an "l", and are line sensors. The center point is located at approximately the central circular etching, but might be displaced slightly due to manufacturing tolerances and/or some limited shifting from impact during shipping or use.

3. All AF sensors detect contrast borders across their areas, and are most sensitive to such borders at right angles to the sensor "lines", so cross-type sensors will look for contrast borders within their areas, but will be most sensitive to higher contrast, and borders that are closest to vertical or horizontal. The line sensors will be most sensitive to contrast borders that are closest to horizontal. The center sensor doesn't much care between horizontal or vertical since the two perpendicular "lines" are of about equal length, but the surrounding cross-type sensors might show some bias from their actual shape and positioning. My guess is that they look for highest contrast first, then, it prioritizes to lower contrast borders that are closer to either the vertical or horizontal planes relative to the viewfinder orientation. Remember that anything within the AF sensor's area is fair game, so make sure that the area that you want to focus on is the dominant one, either by degree of contrast, orientation to vert or horiz, or both.

At this point, let me state that I realize that DSLR AF is usually called Phase Detection as opposed to Contrast Detection, but this terminology has more to do with how the AF system controls the AF motor than how it detects focus. . .this photography stuff can be confusing. . .

Your job as the photographer is to make the camera's AF system work to its greatest potential and accuracy.The thinness of the DOF for a wide aperture lens has been discussed, and I won't repeat it. Also the benefits and detractions of "focus and recompose" has been argued ad ifinitum elsewhere, so I'll defer to those with more exacting requirements than I. Others will argue that the only way is MF, but I can't do it very well, especially in low light, so I'll just discuss AF. . .

What I'd try first is focus and recompose. This is the easiest to learn, the least fiddly and potentially confusing while shooting, and is good enough for most shooters and situations. Keep in mind that what you need to concentrate on is getting the area you want in focus in the central circular etching, actuate AF, wait for a lock (indicated by the steadily lit green hexagon, not the little red light that flashes on), recompose the frame while holding the shutter at half press, then fully depress to take the shot you want. Realize that closer distances and wider apertures both make DOF thinner (there are other factors, but these are probably the most important to remember), so if the DOF is too thin to get the eyes in focus, one strategy would be to back off, take the shot, then crop to get the composition that you want. The alternative is to use a smaller aperture, but in available light shooting, this will make for longer shutter speeds which can make camera shake more of an issue, you have to decide.

You might find this technique doesn't work for you -- an alternative is to first compose the frame, then select the focus point you want the AF system to use by manually selecting your focus point. This is going to be more accurate technically, but has the downsides of potentially being slower, more fiddly and confusing, and uses sensor areas that might be a bit less sensitive and/or accurate. You really can only decide by trying them both. . .

Remember to try to get a high contrast border within the area of the focus sensor, and that they prefer borders that are vertical or horizontal. You might try the border between the iris and the white of the eye, or the eyelid and the white as focusing points when you're at close shooting distances like this. If you're shooting something that has less contrast, and the AF has a problem locking, it might help to twist the camera slightly to get the border to more closely align to the focus sensor orientation (either straight v or h), then tilt the camera back to straight, once you've locked focus.

Sorry for the wordy post -- hope it might help. . .If you already knew this stuff, then you can just disregard it. . .

Scott
07-01-2010, 02:05 AM - 1 Like   #19
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My guess is misfocus and/or subject movement. I sometimes have these kind of "technically bad" pictures even at f4... a very slight movement of my toddler (or myself between focusing and actually releasing the shutter) is enough to have her face blurry. I lock focus and in that 0.3sec to release the shutter she makes a small sudden move (slightly turning her head in other direction is enough) and the photo is screwed up... or focus wasn't even locked at the right distance to begin with, because the AF sensor covers a larger area than the intended target (her eye) and in the viewfinder focus seems to be ok.

07-01-2010, 03:40 AM   #20
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If I ever get pictures which are slightly out of focus (happens more than I'd like ), next time I do what everybody has suggested with deepening depth of field, etc.

But that doesn't really help with your current picture, does it? You could apply sharpening / unsharp mask in whatever post processing program you use, but sometimes that makes the picture look strange or grainy. What I do is turn the picture into a high contrast black and white (although I suppose any artsy effect might help cover up). I don't know if you're into that sort of look, but to my eyes, when I get the focus wrong, it does a decent job of hiding the fact that I am a poor photographer
07-01-2010, 04:44 AM   #21
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Guys
All I can say: I love you all, it is overwhelming, so much info...
I'll stop down in the near future, manual focus is out of question as she is anything but stationery. How can I include the exif data? I thought my signature is a give away: I'm using K7. . thanks thanks and thanks.I only have this camera for a months or more time, is flying with it.The center red little square is lit up only. I use no PP at all. I think I got enough info to try for a couple of weeks. Maybe the 30 % was a bit of understatement it is more like 50%, but that's shameful. I got all the armour now... so this wekend will be a lot more fruitfull..... regards zoltan
07-01-2010, 06:57 AM   #22
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Hi again
I was wrong it was shoot at f 1.7
Attached Images
 
07-01-2010, 07:18 AM   #23
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QuoteOriginally posted by Ben_Edict Quote
A portrait shot (or any other photograph) is not about using the maximum sharpness of a lens, but about achieving a certain visual goal. Therefor using f/1.4 has its own uses and merrits.
Especially for portraits the increased aberrations and the slight loss of contrast can produce very flattering and desirable results.

One should only "generally" do something, if one is prepared to deviate from these "general" rules, to achieve something else.

I would also emphasize, that with this particular image the real problem is not the f-stop, but the general misfocus.

Ben
Yes Ben I think you right, it is misfocus, I think I also left it AF-C, and yes I just wanted to be her eyes to be sharp and nothing else, so that's why I used f1.7
( sorry I said the wrong thing f1.4) so many of you said to :recompose and that is what I will do try to do, and get the focus right

07-01-2010, 07:48 AM   #24
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QuoteOriginally posted by auspentax Quote
Caught myself out for a while when I first went digital, the camera was doing things OK, but not where I wanted.
Sounds obvious, but make sure that the eyepiece diopter is focused too, or you might think you are auto focusing sharp on the right point but you are not.

Easy to do, just push the shutter button halfway down and look at the figures along the bottom in the eyepiece, focus the diopter till they are sharp, job done.
Can do with the lens cap on, probably better as you are not disctracted by what appears via the lens.
Oohh ... how good that is, of couse I done that when I started to use the camera, but I just checked it.. and it was not a 100% good, probably the exitment from the new camera
07-01-2010, 01:32 PM   #25
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My advice:

1) No auto ISO. Turn that off, and select your ISO speed based on where you're shooting. Outside in good sun, 200 to 400. Inside, 800 to 1600. And make sure your pop-up flash is set to manual. In other words, don't use your flash at all for now.

2) Shoot in Av mode to start with. If you're shooting a fast-running jogger or kid, shoot in Tv mode (shutter priority).

This will keep you busy for now while you shoot, post your photos, and folks can comment on your results.
07-01-2010, 07:21 PM   #26
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QuoteOriginally posted by lensego Quote
Guys
All I can say: I love you all, it is overwhelming, so much info...
I'll stop down in the near future, manual focus is out of question as she is anything but stationery. l..... regards zoltan
Actually, in many cases, Manual focus is your best bet. I would highly recommend practicing with it..

Click photo for much larger size....




Taken with a Vivitar 28mm f2.5 Manual focus Screw mount lens (No focus trap for those who may be wondering). I tend to aim for his collar. While it may not be razor sharp, I'll guarantee he's moving faster than Junior is (and he can turn his head and go the other way just as fast).

AF is a good tool to have but it isn't the end-all be-all. Sometimes going back to the basics works the best.

07-02-2010, 02:53 AM   #27
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I just saw that you had it set for Hard sharpness.

Bad idea. Use the lowest setting for that.
07-02-2010, 03:19 AM   #28
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QuoteOriginally posted by Ira Quote
I just saw that you had it set for Hard sharpness.

Bad idea. Use the lowest setting for that.
I am curious, why is hard sharpness bad? Does it result in JPEG artifacts? I'm assuming the RAW image wouldn't be affected...or would it..?
07-02-2010, 06:50 AM   #29
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QuoteOriginally posted by ChooseAName Quote
I am curious, why is hard sharpness bad? Does it result in JPEG artifacts? I'm assuming the RAW image wouldn't be affected...or would it..?
If a shot isn't in focus, hard sharpness is just going to make it look bad in a different way.

If you take a normal, in focus image into an imaging editing program and hit "Sharpen" a few times, the image gradually gets worse each time. Digital sharpening is something to use sparingly--and only when it actually works for the image.

I don't really know how a DSLR handles onboard sharpening as opposed to an image editing program, and I don't know if that sharpening applies to the RAW file. You might be right, that it doesn't at all.
07-02-2010, 09:41 AM   #30
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QuoteOriginally posted by Ira Quote
I don't really know how a DSLR handles onboard sharpening as opposed to an image editing program, and I don't know if that sharpening applies to the RAW file. You might be right, that it doesn't at all.
If I look at the PEF file vs the JPG file in a preview (windows explorer, Win7), they are clearly different. I mention that to suggest that the camera settings do not affect the RAW (PEF) file. Things like WB and exposure are retained but that's about it.

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