That old lens problem page 1
Cunt
3rd February 2012, 01:02 AM
So I bought an old lens. Specifically, it is a manual focus f1.2 50mm.
It has an interesting problem now that camera technology has advanced. I will see if I can explain it adequately without resorting to linking references...
The DoF available with an f1.2 is fucking unreal (lets say, 1cm at 1m, just to make up numbers to use). The viewfinder on my Pentax (and all dSLR's today) can 'see' down to about f1.9 or so...maybe f2.8 (lets say, 4cm at 1m) What this means is that I have to 'bracket' my focus point to be sure I have what I want in focus. (it also means that I can see through those super-zooms, so I understand Pentax and others making the compromise)
Now, about bracketing. The military used to use the method for dropping artillery on stuff. By the fourth or fifth shot, you were ranged and going to get dead. Nowadays, they get you in two (sometimes one). What I am hoping is that there is some math trick that allowed them to make that advance, which might be applicable to my lens/camera.
Have any of you got experience with using this kind of lens with this kind of (BEAUTIFUL) problem?
By the way, there is a product called 'Katz-eye' which I can install which will get me closer to seeing properly, but I would rather find a math answer, because it might be a lot cheaper.
Oh, and it IS worth it when it nails the focus...
http://i234.photobucket.com/albums/ee174/Darren8306/_DJK8453.jpg
It has an interesting problem now that camera technology has advanced. I will see if I can explain it adequately without resorting to linking references...
The DoF available with an f1.2 is fucking unreal (lets say, 1cm at 1m, just to make up numbers to use). The viewfinder on my Pentax (and all dSLR's today) can 'see' down to about f1.9 or so...maybe f2.8 (lets say, 4cm at 1m) What this means is that I have to 'bracket' my focus point to be sure I have what I want in focus. (it also means that I can see through those super-zooms, so I understand Pentax and others making the compromise)
Now, about bracketing. The military used to use the method for dropping artillery on stuff. By the fourth or fifth shot, you were ranged and going to get dead. Nowadays, they get you in two (sometimes one). What I am hoping is that there is some math trick that allowed them to make that advance, which might be applicable to my lens/camera.
Have any of you got experience with using this kind of lens with this kind of (BEAUTIFUL) problem?
By the way, there is a product called 'Katz-eye' which I can install which will get me closer to seeing properly, but I would rather find a math answer, because it might be a lot cheaper.
Oh, and it IS worth it when it nails the focus...
http://i234.photobucket.com/albums/ee174/Darren8306/_DJK8453.jpg
FedUpWithFaith
3rd February 2012, 01:18 AM
Cunt,
i saw you asked me in another thread to check this question. Unfortunately I probably can't help you. I haven't done advanced optics for a long time and i was never much into photography at any fancy level.
I'm also not sure I really understand your question. I'm not sure I understand precisely what you want to calculate and what the trade-offs are. As you probably know, not all lenses of any particular rating (speed, FOV, DOF, zoom range) are created equal. All modern lenses are composites designed to compensate for various forms of optical aberration and distortion, color compensation, glare/anti-reflection and other shit I've forgotten probably. There are always trade-off with some lenses favoring one type of aberration over another. Since it sounds like you're dealing with an SLR that means you have potential interface contributions from the internal camera optics (those this may be irrelevant, I can't remember the standard SLR optical train and it may have nothing to do with the end product, only the difference in eye inspection and what the photo looks like.
Anyway, wish I could help but probably no help at all.
i saw you asked me in another thread to check this question. Unfortunately I probably can't help you. I haven't done advanced optics for a long time and i was never much into photography at any fancy level.
I'm also not sure I really understand your question. I'm not sure I understand precisely what you want to calculate and what the trade-offs are. As you probably know, not all lenses of any particular rating (speed, FOV, DOF, zoom range) are created equal. All modern lenses are composites designed to compensate for various forms of optical aberration and distortion, color compensation, glare/anti-reflection and other shit I've forgotten probably. There are always trade-off with some lenses favoring one type of aberration over another. Since it sounds like you're dealing with an SLR that means you have potential interface contributions from the internal camera optics (those this may be irrelevant, I can't remember the standard SLR optical train and it may have nothing to do with the end product, only the difference in eye inspection and what the photo looks like.
Anyway, wish I could help but probably no help at all.
Cunt
3rd February 2012, 01:46 AM
I'm also not sure I really understand your question. I'm not sure I understand precisely what you want to calculate and what the trade-offs are.
The DoF available in the viewfinder is about f2 while the DoF available in the lens is f1.2 (smaller slice of focus/bigger hole)
The 'problem' is the lens which focuses the image onto the viewfinder (part of the camera, not the lens). The thing is compromised to allow you to see enough light through smaller apertures (such as on the super-zooms), and the sacrifice is DoF (though I don't understand how, exactly)
Since it sounds like you're dealing with an SLRdSLR, [/pedant]
that means you have potential interface contributions from the internal camera optics (those this may be irrelevant, I can't remember the standard SLR optical train and it may have nothing to do with the end product, only the difference in eye inspection and what the photo looks like.This is internal camera optics, and does not affect image quality.
Anyway, wish I could help but probably no help at all.
You already helped me explain the question better (I hope) to at least one person. Maybe another one will read this, so thanks.
See, I have to bracket focus at the moment, take several shots adjusting the focus slightly each time, then go look on the computer to see which is in focus.
If I were shooting a ruler, the DoF through the viewfinder would look like 4cm, while in the photo it would be 1cm. Bracketing more efficiently (or learning some other optical trick) might improve my 'hit' rate...
The DoF available in the viewfinder is about f2 while the DoF available in the lens is f1.2 (smaller slice of focus/bigger hole)
The 'problem' is the lens which focuses the image onto the viewfinder (part of the camera, not the lens). The thing is compromised to allow you to see enough light through smaller apertures (such as on the super-zooms), and the sacrifice is DoF (though I don't understand how, exactly)
Since it sounds like you're dealing with an SLRdSLR, [/pedant]
that means you have potential interface contributions from the internal camera optics (those this may be irrelevant, I can't remember the standard SLR optical train and it may have nothing to do with the end product, only the difference in eye inspection and what the photo looks like.This is internal camera optics, and does not affect image quality.
Anyway, wish I could help but probably no help at all.
You already helped me explain the question better (I hope) to at least one person. Maybe another one will read this, so thanks.
See, I have to bracket focus at the moment, take several shots adjusting the focus slightly each time, then go look on the computer to see which is in focus.
If I were shooting a ruler, the DoF through the viewfinder would look like 4cm, while in the photo it would be 1cm. Bracketing more efficiently (or learning some other optical trick) might improve my 'hit' rate...
FedUpWithFaith
3rd February 2012, 01:51 AM
OK, i think I'm getting closer to getting you but let me seek a little more clarification. You are getting a mismatch between what you see in the viewfinder as opposed to what you see in the end-product image. Correct?
If yes, I'm still confused as to whther it is a focus issue, a field of view issue, or both.
Or am i still tits up altogether?
If yes, I'm still confused as to whther it is a focus issue, a field of view issue, or both.
Or am i still tits up altogether?
Cunt
3rd February 2012, 03:27 AM
It is just as you say. When the mirror moves over and lets the light hit the sensor ('film'), everything is fine. When it hits the mirror and travels up into the lens (the replaceable bit inside the camera (http://www.katzeyeoptics.com/item--Pentax-K-5-K-7-Focusing-Screen--prod_K7.html)) it gets a different DoF.
FedUpWithFaith
3rd February 2012, 05:14 AM
It is just as you say. When the mirror moves over and lets the light hit the sensor ('film'), everything is fine. When it hits the mirror and travels up into the lens (the replaceable bit inside the camera (http://www.katzeyeoptics.com/item--Pentax-K-5-K-7-Focusing-Screen--prod_K7.html)) it gets a different DoF.
Is focus offset too? you didn't say.
Funny thing is I had an older Pentax that had the same problem. only i didn't know it was a problem and still don't. I figured that's just the way it was made ( calibrated). I didn't know better because it was the first and only SLR camera I ever bought I had different telephotos for it and none of them ever matched. i just learned to adjust to it.
Is focus offset too? you didn't say.
Funny thing is I had an older Pentax that had the same problem. only i didn't know it was a problem and still don't. I figured that's just the way it was made ( calibrated). I didn't know better because it was the first and only SLR camera I ever bought I had different telephotos for it and none of them ever matched. i just learned to adjust to it.
FedUpWithFaith
3rd February 2012, 05:18 AM
OK, I might know the problem IF you don't have a simultaneous focus problem. I think most SLRs use a relay prism. it would be in the body of the camera. if its on a slider it might have moved. it;s the only thing i can think of. it would probably be sealed in the slider if I'm right. it might not be made for user adjustment and even if you could access the set screws, this is probably not something you should fuck with.
Call Pentax.
Call Pentax.
Cunt
3rd February 2012, 05:19 AM
As far as I can tell, the focus isn't offset, simply that the viewfinder shows a fatter depth of field when I have the aperture open that much.
It doesn't come up much. Most lenses are within the range of the (inside-camera-body) lens that comes with it. This thing has a REALLY large aperture.
For instance, we use the older flourescents in our office, and when I take off the lens cap, you can just see the room get darker. I don't have the figure, but it takes a whale of a lot of photons to fill that barrel.
It doesn't come up much. Most lenses are within the range of the (inside-camera-body) lens that comes with it. This thing has a REALLY large aperture.
For instance, we use the older flourescents in our office, and when I take off the lens cap, you can just see the room get darker. I don't have the figure, but it takes a whale of a lot of photons to fill that barrel.
Cunt
3rd February 2012, 05:20 AM
this isn't a malfunction, it is a limit of the lens inside the camera body.
I have been using bracketing as a workaround, and I thought math might yield a better method and save me buying that (lens inside the camera body) focussing screen.
I have been using bracketing as a workaround, and I thought math might yield a better method and save me buying that (lens inside the camera body) focussing screen.
FedUpWithFaith
3rd February 2012, 05:26 AM
this isn't a malfunction, it is a limit of the lens inside the camera body.
I have been using bracketing as a workaround, and I thought math might yield a better method and save me buying that (lens inside the camera body) focussing screen.
OK, gotcha.
Go buy a dark grease pencil. Remove from wrapper and start doing some Math with it on a piece of paper - maybe some simple addition. As you draw the numbers be sure to tilt the pencil so the grease get sharpened to the thickness of the area you've bracketed away. Now take the grease pencil and draw a border around your viewfinder.
Problem solved.
I have been using bracketing as a workaround, and I thought math might yield a better method and save me buying that (lens inside the camera body) focussing screen.
OK, gotcha.
Go buy a dark grease pencil. Remove from wrapper and start doing some Math with it on a piece of paper - maybe some simple addition. As you draw the numbers be sure to tilt the pencil so the grease get sharpened to the thickness of the area you've bracketed away. Now take the grease pencil and draw a border around your viewfinder.
Problem solved.
Sentinel
3rd February 2012, 06:18 PM
Which Pentax are you shooting, C?
Cunt
3rd February 2012, 11:10 PM
K-5
Sentinel
4th February 2012, 05:41 AM
Have you tried using the DOFP in live view?
Cunt
4th February 2012, 06:07 AM
Yup. No better though.
Sentinel
4th February 2012, 06:49 AM
Welp, then I got nothing.
Maybe over time you'll learn to eye-ball it?
Maybe over time you'll learn to eye-ball it?
Cunt
4th February 2012, 07:05 AM
bracketing, and that practice you mentioned. A KatzEye optics internal lens if I win the lotto...
Sentinel
7th February 2012, 07:15 PM
Depth of Field Calculator (http://www.dofmaster.com/dofjs.html)
might help
might help
Cunt
7th February 2012, 08:49 PM
Thanks, but that just quantifies the problem. The lens 'sees' DoF to f1.2, but the viewfinder only 'sees' DoF to f2 (approximately)
Sentinel
8th February 2012, 10:42 PM
have you asked at pentaxforums.com? (http://www.pentaxforums.com)
Cunt
9th February 2012, 01:58 AM
I have read, but don't think I have asked. I thought photographers would be less helpful than non-photographers. I think the solution could be math, but the knowledge might come from anywhere.
Photographers are a diverse, smart bunch. They have worked this problem.
I used to think the Pythagoreum Theorum was cool until I found out it wasn't a theorum. The fuckers had proof, so says wiki, back in the days of Pythagoras.
Anyway, back when I thought it was cool, I told my younger brother about it, explaining why I liked it so much.
My little brother, who is a concrete worker, showed me the 3 4 5 thing. You make a corner, then measure each side you want to be 90. One should be three, the other four, may the other side 5 and your corner is square. Inches, feet or meters works for this.
Basically, I daydreamed about those triangles and the theory describing them, and he used a real one every day.
Someone out there uses this bracketing formula on something else and if I find it, I can map it over to mine. The only other way would be to learn enough about math. That would be hard.
I just sent my camera out for repair anyway, so I won't need to worry about it for awhile.
Photographers are a diverse, smart bunch. They have worked this problem.
I used to think the Pythagoreum Theorum was cool until I found out it wasn't a theorum. The fuckers had proof, so says wiki, back in the days of Pythagoras.
Anyway, back when I thought it was cool, I told my younger brother about it, explaining why I liked it so much.
My little brother, who is a concrete worker, showed me the 3 4 5 thing. You make a corner, then measure each side you want to be 90. One should be three, the other four, may the other side 5 and your corner is square. Inches, feet or meters works for this.
Basically, I daydreamed about those triangles and the theory describing them, and he used a real one every day.
Someone out there uses this bracketing formula on something else and if I find it, I can map it over to mine. The only other way would be to learn enough about math. That would be hard.
I just sent my camera out for repair anyway, so I won't need to worry about it for awhile.
Hermit
9th February 2012, 01:51 PM
I used to think the Pythagoreum Theorum was cool until I found out it wasn't a theorum. The fuckers had proof, so says wiki, back in the days of Pythagoras.
Anyway, back when I thought it was cool, I told my younger brother about it, explaining why I liked it so much.
My little brother, who is a concrete worker, showed me the 3 4 5 thing. You make a corner, then measure each side you want to be 90.
The Pythagorean theorem is a theorem. It posits that a^2 + b^2 = c^2\. There are at least five proofs for it. The method of connecting three lines with the length ratio of 3:4:5 is a practical way of creating a 90° angle. (Curiously, the other two are approximately 36.86° and 53.13°.) That is not what the Pythagorean theorem is about. It just requires right angles for it to work.
Anyway, back when I thought it was cool, I told my younger brother about it, explaining why I liked it so much.
My little brother, who is a concrete worker, showed me the 3 4 5 thing. You make a corner, then measure each side you want to be 90.
The Pythagorean theorem is a theorem. It posits that a^2 + b^2 = c^2\. There are at least five proofs for it. The method of connecting three lines with the length ratio of 3:4:5 is a practical way of creating a 90° angle. (Curiously, the other two are approximately 36.86° and 53.13°.) That is not what the Pythagorean theorem is about. It just requires right angles for it to work.
Cunt
22nd May 2012, 02:08 PM
I have my camera body back and have been practicing a bit. I thought I would share some of what I have gotten out of it lately.
http://jacquard.ca/SimpleProsperousFire/images/DJK55548.jpg
http://jacquard.ca/SimpleKuzmanBirthday2012/images/DJK55701.jpg
http://jacquard.ca/SimpleKuzmanBirthday2012/images/DJK55629.jpg
I am still missing a lot, but practice is beginning to pay off.
http://jacquard.ca/SimpleProsperousFire/images/DJK55548.jpg
http://jacquard.ca/SimpleKuzmanBirthday2012/images/DJK55701.jpg
http://jacquard.ca/SimpleKuzmanBirthday2012/images/DJK55629.jpg
I am still missing a lot, but practice is beginning to pay off.
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