Positioning DoF

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benlonghair

benlonghair

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What's the best way to test this? Set up a target of some sort, focus on it manually and see the results?
 

Flash Harry

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1/3 in front and 2/3 behind the point of sharp focus is the old rule, this is why we focus 1/3 into an image, the eyes of a person for example, everything else either towards or away from this area will drop off depending on your aperture or distance to subject, which is the reason most pros do not shoot wide open unless distance to subject will allow it.

On another note I think you need both camera and lens recalibrated if sharp focus is not achieved on the subject you shot, try stopping down slightly for critical focus. H
 

OrionsByte

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I may be over-simplifying the problem or not understanding it correctly, but if the problem was with the lens, wouldn't that be apparent in the viewfinder as well? I mean, if the focal plane looks right in the viewfinder, it should look right in the picture... right? It sounds like what you're saying is you focus on something, say, 10' away, but the pictures come out looking like you focused on something 10' 6" away. Regardless of DOF (which could just be making the problem easier to see rather than being the problem itself), the focal plane shouldn't be any different between the viewfinder and the photo because it's all coming from the same lens.

Not to insult your intelligence or anything, but could this be as simple as a diopter adjustment to the viewfinder? I'm new to DSLRs so there may be something important that I'm not understanding properly, but sometimes the easiest solutions are the ones most overlooked.
 

Derrel

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>SNIP>

Not to insult your intelligence or anything, but could this be as simple as a diopter adjustment to the viewfinder? I'm new to DSLRs so there may be something important that I'm not understanding properly, but sometimes the easiest solutions are the ones most overlooked.

I was going to ask the same question--is the viewfinder's diopter adjustment set correctly for Infinity focus with your vision or eyeglasses, if you wear corrective lenses???? I once got my D2x's diopter out of whack somehow, and shot a bunch of photos using a manual focus 400mm lens, and they were OOF when I got back to the computer...
 

Gaerek

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>SNIP>

Not to insult your intelligence or anything, but could this be as simple as a diopter adjustment to the viewfinder? I'm new to DSLRs so there may be something important that I'm not understanding properly, but sometimes the easiest solutions are the ones most overlooked.

I was going to ask the same question--is the viewfinder's diopter adjustment set correctly for Infinity focus with your vision or eyeglasses, if you wear corrective lenses???? I once got my D2x's diopter out of whack somehow, and shot a bunch of photos using a manual focus 400mm lens, and they were OOF when I got back to the computer...

I thought this too, but he said it happens with AF and MF both. If that's the case, the diopter would only affect MF.
 

Derrel

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Hmmm....the OP is a slight bit confusing to me, but it sounds like it might be a case of back-focusing. Have you set the shutter on B for Bulbm, pressed the shutter release, allowed the mirror to swing up, and then blown or brushed out AF sensor module area located at the bottom center of the mirror box??? Is there some dust or debris there, in front of the AF sensor???

ALSO, and this is a possibility that just occurred to me--is the viewfinder focusing SCREEN firmly latched into place and riding properly in its frame???? That is one thing that would affect both AF and MF focus ascertainment, if the viewfinder's focusing screen were slightly out of position, the focus ascertainment would be out of whack in AF and MF.

Has the camera been dropped? Has it been loaned out? Has it been checked for demonic possession, or the much more likely culprit, gremlins???
 

OrionsByte

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>SNIP>

Not to insult your intelligence or anything, but could this be as simple as a diopter adjustment to the viewfinder? I'm new to DSLRs so there may be something important that I'm not understanding properly, but sometimes the easiest solutions are the ones most overlooked.

I was going to ask the same question--is the viewfinder's diopter adjustment set correctly for Infinity focus with your vision or eyeglasses, if you wear corrective lenses???? I once got my D2x's diopter out of whack somehow, and shot a bunch of photos using a manual focus 400mm lens, and they were OOF when I got back to the computer...

I thought this too, but he said it happens with AF and MF both. If that's the case, the diopter would only affect MF.

That occurred to me, except he said when he focused on the grass behind the dog the focus looked okay. I don't know if that means he was using AF or MF at the time, and whether it looked okay before or after the shot. So I thought I'd toss out the suggestion anyways just in case.

And if it's not the viewfinder, what would make it look correct in the viewfinder but not okay in the photo? Like I said, there's no reason for the focal point to change just because the curtain's up, so I'm guessing there's something wrong with the viewfinder optics.

He also said his other lenses appear fine, but that could be because they have a larger minimum aperture so the problem isn't as noticeable compared to an f/1.8.
 

Gaerek

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I was going to ask the same question--is the viewfinder's diopter adjustment set correctly for Infinity focus with your vision or eyeglasses, if you wear corrective lenses???? I once got my D2x's diopter out of whack somehow, and shot a bunch of photos using a manual focus 400mm lens, and they were OOF when I got back to the computer...

I thought this too, but he said it happens with AF and MF both. If that's the case, the diopter would only affect MF.

That occurred to me, except he said when he focused on the grass behind the dog the focus looked okay. I don't know if that means he was using AF or MF at the time, and whether it looked okay before or after the shot. So I thought I'd toss out the suggestion anyways just in case.

This was from one of his earlier posts:

Both AF and MF have this problem.

So only going off of that. If he says both have the problem, I'll assume that both have the problem.

And if it's not the viewfinder, what would make it look correct in the viewfinder but not okay in the photo? Like I said, there's no reason for the focal point to change just because the curtain's up, so I'm guessing there's something wrong with the viewfinder optics.

Look at an image on your LCD. Then look at the same image fitted to the screen on your monitor. The image on your LCD probably has a lot more areas that look sharp than on your monitor. I personally find it difficult to determine everything that is or isn't in focus, through the viewfinder, especially with regards to DoF. I understand that the image in the viewfinder and the image that is produced should look the same, but determining the exact amount of focus of everything in the image can be difficult through the viewfinder.

He also said his other lenses appear fine, but that could be because they have a larger minimum aperture so the problem isn't as noticeable compared to an f/1.8.

I don't mean to nitpick, but you probably mean a smaller minimum aperture? I don't think there are any non-primes with a larger minimum aperture than 2.0. Chances are, unless he shoots all primes, all of his lenses will have a smaller minimum aperture (larger f-number).

Like I said, I'm going to rule out the diopter simply because he said the problem is both AF/MF. I could very well be wrong. This who issue is very difficult to make a call on, simply because we don't have any pictures to evaluate or anything like that. You very well could be right, but I'm just going to go off of the information as presented.
 

OrionsByte

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He also said his other lenses appear fine, but that could be because they have a larger minimum aperture so the problem isn't as noticeable compared to an f/1.8.

I don't mean to nitpick, but you probably mean a smaller minimum aperture? I don't think there are any non-primes with a larger minimum aperture than 2.0. Chances are, unless he shoots all primes, all of his lenses will have a smaller minimum aperture (larger f-number).

I'm sorry, yes, I reversed my train of thought mid-sentence (probably a good reason why I shouldn't post from work). What I meant to say was that the large aperture on the f/1.8 lens might just be obviating a problem with the camera that isn't as apparent on the other lenses, since the additional depth of field from their smaller apertures could make a slight focusing problem harder to detect.

Thanks for the correction though.
 

fokker

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Sounds like user error to me - it's pretty hard to accurately manul focus a camera like D60. Even if what you think you're focuing on looks sharp in the viewfinder chances are it won't be perfect when you see it larger.

If you're having the problem with manual focus it cannot possibly a camera/lens calibration issue - what you see is what you get with manual focus. (unless your diopter is out of whack, in which case fix it!)
 

Gaerek

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I'm sorry, yes, I reversed my train of thought mid-sentence (probably a good reason why I shouldn't post from work). What I meant to say was that the large aperture on the f/1.8 lens might just be obviating a problem with the camera that isn't as apparent on the other lenses, since the additional depth of field from their smaller apertures could make a slight focusing problem harder to detect.

Thanks for the correction though.

No problem, I thought this was the case. :)

I'm just a bit OCD when it comes to using jargon. Like when someone tells me they download pictures to their computer...that one irritates me to no end. :x
 

fokker

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Like when someone tells me they download pictures to their computer...that one irritates me to no end. :x

Whats wrong with that? :scratch:
 

Gaerek

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Downloading is bringing data from somewhere.

Uploading is moving data to somewhere.

To use the phrase I posted earlier properly you have 2 choices:

1) I uploaded pictures to my computer.

Or

2) I downloaded pictures from my camera.

I'm in IT, and it annoys the crap out of me when people use download to mean moving data both downstream AND upstream. Another one that annoys me is when people call those wireless cell phone headsets "a Bluetooth." Bluetooth is a wireless protocol people! Not a piece of hardware!

:soapbox:

Nerd rant over...now back to your regularly scheduled thread. :)
 

pbelarge

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I'm just a bit OCD when it comes to using jargon. Like when someone tells me they download pictures to their computer...that one irritates me to no end. :x


There is medication for this :mrgreen:


Maybe I am completely wrong, but could his camera be off focus, creating this problem??
 

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