tlitody
Well-known
An extract from Zeiss camera Lens News:
Depth of Field – An Insider’s Look Behind The Scenes
Maybe the same thing happened to you recently: Upon receiving some rolls of film back from processing, you briefly check the color rendition, and then examine the new images with an 8x magnifying loupe for fine detail, for sharpness.
Every once in a while you may encounter an image with double contours and you know immediately that some bad vibration tricked you. But you may also find images that show stunning sharpness in some areas, whereas detail resolution in other areas does not meet your expectations. When you took those photos you knew exactly what depth of field you were after and with the help of the depth of field scale on your lens or the table supplied with it you set the aperture and the correct focus accordingly. However, the result is disappointing.
If images like this accumulate, you suspect your lens to be at fault and turn it in. You mail it to Contax or Hasselblad or Carl Zeiss. Be assured it will be in good company: "Depth of field is insufficient“ is the most common complaint to meet the Carl Zeiss service department today. And there is an upward trend. Why? To find the answer, let’s take a short look at the basics:
• In your image the one plane will be perfectly sharp that you set the focus for.
• Everything on either side of that plane will come out blurred, more or less.
• How much a subject detail is blurred, depends mainly on its distance to this plane of perfect sharpness, and on the aperture setting, and the focus setting.
• A certain amount of blur is supposed to be tolerable. According to international standards the degree of blur tolerable is defined as 1/1000th of the camera format diagonal, as the normally satisfactory value. With 35 mm format and its 43 mm diagonal only 1/1500th is deemed tolerable, resulting in 43 mm/1500 » 0.030 mm = 30 μm of blur.
Imagine the very tip of a pin with a size of exactly zero, located precisely in the plane of perfect sharpness, that means, it is imaged to the film with a size of exactly zero, not widened by any blur. Now, move this pin towards the camera and watch the diameter of its tip increase by blurring. When it has reached 30 μm, halt the pin! It is now right at the inner border of the depth of field. Now, do the same in the opposite direction. Beyond the plane of perfect sharpness you will reach the outer border of the depth of field.
All the photo school books in the world explain that same principle and tell a similar story, although with different words and sketches and images. And all the camera lens manufacturers in the world including Carl Zeiss have to adhere to the same principle and the international standard that is based upon it, when producing their depth of field scales and tables. But here’s what the school books don’t tell:
A blur tolerable of 30 μm equals a resolution of 30 line pairs per millimeter (lp/mm). The normally satisfactory value was standardized with the film’s imaging quality in mind – at the time the standard was defined which was long before World War II! Meanwhile some decades have passed, today’s color films easily resolve 120 lp/mm and more, with Kodak Ektar 25 and Royal Gold 25 leading the field at 200. Four-color printing processes have also improved vastly and so have our expectations about sharpness. The depth of field standard, however, has remained unchanged…
This is still absolutely okay as far as the large majority of photo amateurs is concerned, that take their photos without tripods and have them printed no larger than 4 x 6. Be aware that these amateurs represent 90% of all picture takers, so don’t expect the depth of field standard to change fundamentally before long, creating a reason for the camera lens manufacturers to introduce new depth of field scales. If you are not satisfied with the results you achieve using the existing scales, tables, and formulas, keep tuned to CLN. We will provide you with information on how to achieve utmost sharpness in photographic images.
Let’s sum it up for today:
• The international depth of field standard, the basis for all camera lens manufacturers to calculate their depth of field scales and tables, dates back from a time, when image quality was severely limited by the films available.
• Those who use depth of field scales, tables, and formulas (e. g. for hyperfocal settings), restrict themselves – most probably without knowing why – to the image quality potential of an average pre-World-War-II emulsion.
Now isn't that interesting. The resolution of film is very important and the DoF scales were designed with it in mind. But it seems if you increase the resolution by increasing the pixel count of a sensor that doesn't count, according to some.
Depth of Field – An Insider’s Look Behind The Scenes
Maybe the same thing happened to you recently: Upon receiving some rolls of film back from processing, you briefly check the color rendition, and then examine the new images with an 8x magnifying loupe for fine detail, for sharpness.
Every once in a while you may encounter an image with double contours and you know immediately that some bad vibration tricked you. But you may also find images that show stunning sharpness in some areas, whereas detail resolution in other areas does not meet your expectations. When you took those photos you knew exactly what depth of field you were after and with the help of the depth of field scale on your lens or the table supplied with it you set the aperture and the correct focus accordingly. However, the result is disappointing.
If images like this accumulate, you suspect your lens to be at fault and turn it in. You mail it to Contax or Hasselblad or Carl Zeiss. Be assured it will be in good company: "Depth of field is insufficient“ is the most common complaint to meet the Carl Zeiss service department today. And there is an upward trend. Why? To find the answer, let’s take a short look at the basics:
• In your image the one plane will be perfectly sharp that you set the focus for.
• Everything on either side of that plane will come out blurred, more or less.
• How much a subject detail is blurred, depends mainly on its distance to this plane of perfect sharpness, and on the aperture setting, and the focus setting.
• A certain amount of blur is supposed to be tolerable. According to international standards the degree of blur tolerable is defined as 1/1000th of the camera format diagonal, as the normally satisfactory value. With 35 mm format and its 43 mm diagonal only 1/1500th is deemed tolerable, resulting in 43 mm/1500 » 0.030 mm = 30 μm of blur.
Imagine the very tip of a pin with a size of exactly zero, located precisely in the plane of perfect sharpness, that means, it is imaged to the film with a size of exactly zero, not widened by any blur. Now, move this pin towards the camera and watch the diameter of its tip increase by blurring. When it has reached 30 μm, halt the pin! It is now right at the inner border of the depth of field. Now, do the same in the opposite direction. Beyond the plane of perfect sharpness you will reach the outer border of the depth of field.
All the photo school books in the world explain that same principle and tell a similar story, although with different words and sketches and images. And all the camera lens manufacturers in the world including Carl Zeiss have to adhere to the same principle and the international standard that is based upon it, when producing their depth of field scales and tables. But here’s what the school books don’t tell:
A blur tolerable of 30 μm equals a resolution of 30 line pairs per millimeter (lp/mm). The normally satisfactory value was standardized with the film’s imaging quality in mind – at the time the standard was defined which was long before World War II! Meanwhile some decades have passed, today’s color films easily resolve 120 lp/mm and more, with Kodak Ektar 25 and Royal Gold 25 leading the field at 200. Four-color printing processes have also improved vastly and so have our expectations about sharpness. The depth of field standard, however, has remained unchanged…
This is still absolutely okay as far as the large majority of photo amateurs is concerned, that take their photos without tripods and have them printed no larger than 4 x 6. Be aware that these amateurs represent 90% of all picture takers, so don’t expect the depth of field standard to change fundamentally before long, creating a reason for the camera lens manufacturers to introduce new depth of field scales. If you are not satisfied with the results you achieve using the existing scales, tables, and formulas, keep tuned to CLN. We will provide you with information on how to achieve utmost sharpness in photographic images.
Let’s sum it up for today:
• The international depth of field standard, the basis for all camera lens manufacturers to calculate their depth of field scales and tables, dates back from a time, when image quality was severely limited by the films available.
• Those who use depth of field scales, tables, and formulas (e. g. for hyperfocal settings), restrict themselves – most probably without knowing why – to the image quality potential of an average pre-World-War-II emulsion.
Now isn't that interesting. The resolution of film is very important and the DoF scales were designed with it in mind. But it seems if you increase the resolution by increasing the pixel count of a sensor that doesn't count, according to some.
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ampguy
Veteran
interesting
interesting
I would guess that 3d live-view r&d is probably well in progress somewhere.
Some things that exist now, that might sound like bokeh only controls affect dof too - one is the Nikon 105/2 defocus lens with hardware control of spherical abberation - interesting link here:
http://www.stacken.kth.se/~maxz/defocuscontrol/
also, the FujiF70exr I have will let one change the bokeh with 3 setting levels, while keeping the focal length and aperture constant.
I'm tempted to say that this is an example of why bokeh circle sizes have nothing to do with blur circles as used in subjective dof calculations, let alone the obvious fact that it is lens and light point source specific, but don't really want to go there...
interesting
I would guess that 3d live-view r&d is probably well in progress somewhere.
Some things that exist now, that might sound like bokeh only controls affect dof too - one is the Nikon 105/2 defocus lens with hardware control of spherical abberation - interesting link here:
http://www.stacken.kth.se/~maxz/defocuscontrol/
also, the FujiF70exr I have will let one change the bokeh with 3 setting levels, while keeping the focal length and aperture constant.
I'm tempted to say that this is an example of why bokeh circle sizes have nothing to do with blur circles as used in subjective dof calculations, let alone the obvious fact that it is lens and light point source specific, but don't really want to go there...
ampguy
Veteran
right
right
HCB's works were or are considered acceptably sharp for magazine covers by many back in his day.
Today, I would hazard a guess that fewer would find his images acceptably sharp (or unsharp, depending on what you're looking for...)
The fact that Leica states that their lens barrels don't need extra tweaking for the M8, is their company statement on what is acceptably sharp, for the camera they designed. Saying they are wrong about that is no different than saying an HCB photo is unacceptably sharp, or that someone's mother is ugly.
You can say it, but it's just mean. I can take photos, and show that mother is pretty. :angel:
right
HCB's works were or are considered acceptably sharp for magazine covers by many back in his day.
Today, I would hazard a guess that fewer would find his images acceptably sharp (or unsharp, depending on what you're looking for...)
The fact that Leica states that their lens barrels don't need extra tweaking for the M8, is their company statement on what is acceptably sharp, for the camera they designed. Saying they are wrong about that is no different than saying an HCB photo is unacceptably sharp, or that someone's mother is ugly.
You can say it, but it's just mean. I can take photos, and show that mother is pretty. :angel:
I'm thinking that the EP2 (or other camera) can sweep the lens from min to max focus, at maximum aperture. Use spatial gradient for scene segmentation to isolate the areas in focus at each distance. Build up a set of objects along with there distances from the camera. Then, focus on the spot selected for the user for the final image, and build up the preview using the stored objects. Figure 30FPS, to do this- maybe 1-second latency. About the same for Contrast Autofocus lenses now. Maybe they are already doing the 3D scene segmentation, but have not implemented the display routines yet. That would explain why the AF is so slow.
tlitody
Well-known
Just to make sure everyone has the facts:
http://www.zeiss.com/C12567A8003B8B6F/EmbedTitelIntern/CLN_35_Bokeh_EN/$File/CLN35_Bokeh_en.pdf
http://www.zeiss.com/C12567A8003B8B6F/EmbedTitelIntern/CLN_35_Bokeh_EN/$File/CLN35_Bokeh_en.pdf
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ampguy
Veteran
You might want to check this thread out, thanks for the reference to the nice article. It's good to see what people are thinking - regardless of whether they are right or wrong.
http://www.rangefinderforum.com/forums/showthread.php?threadid=91694
http://www.rangefinderforum.com/forums/showthread.php?threadid=91694
antiquark
Derek Ross
Amazing that a mathematical equation is so controversial.
ampguy
Veteran
here's another reply from Leica
here's another reply from Leica
to a customer on the issue -
I am gearing myself mentally up for an extended trip where I will be using my M8 gear (body plus 5 lenses) as my my main camera setup. How accurate is the depth-of-field scale of Leica lenses on the M8? Is the scale on the lenses as accurate as on film M bodies? Any feedback is appreciated.
---End Quote---
-------
-----------------------------------------------
Dear Mr. Watts,
thank you very much for your interest in the Leica system.
No matter if you use an analogue M camera, a Leica M8 with a slightly smaller sensor or the new Leica M9 with full size sensor, the reproduction scale remains the same, if the same focal length is used. That is why the depth of field engravings do not need to be changed, also with your Leica M8, they are still accurate.
Thank you very much for your understanding and have a nice time with your Leica M8.
Mit freundlichen Gruessen / kind regards
Martin Seeliger
Leica Camera AG
Informationsservice
Gewerbepark 8 / D-35606 Solms / Germany
Leica Camera AG (http://www.leica-camera.com) / martin.seeliger@leica-camera.com
Telephone +49(0)6442-208-111 / Fax +49(0)6442-208-339
here's another reply from Leica
to a customer on the issue -
I am gearing myself mentally up for an extended trip where I will be using my M8 gear (body plus 5 lenses) as my my main camera setup. How accurate is the depth-of-field scale of Leica lenses on the M8? Is the scale on the lenses as accurate as on film M bodies? Any feedback is appreciated.
---End Quote---
-------
-----------------------------------------------
Dear Mr. Watts,
thank you very much for your interest in the Leica system.
No matter if you use an analogue M camera, a Leica M8 with a slightly smaller sensor or the new Leica M9 with full size sensor, the reproduction scale remains the same, if the same focal length is used. That is why the depth of field engravings do not need to be changed, also with your Leica M8, they are still accurate.
Thank you very much for your understanding and have a nice time with your Leica M8.
Mit freundlichen Gruessen / kind regards
Martin Seeliger
Leica Camera AG
Informationsservice
Gewerbepark 8 / D-35606 Solms / Germany
Leica Camera AG (http://www.leica-camera.com) / martin.seeliger@leica-camera.com
Telephone +49(0)6442-208-111 / Fax +49(0)6442-208-339
antiquark
Derek Ross
In a technical sense, Leica is lying. In a practical sense, they're telling the truth.