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  1. #181
    kintatsu's Avatar
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    Quote Originally Posted by StoneNYC View Post
    ... Let us pretend that this is a photograph, or a negative, and that the image was taken with both of 35mm and a 4x5. As you can see in the center The man is visible in both the larger format and the smaller format, but the surrounding area is visible only by the larger format film, however where both images line up, within that 35mm frame, the depth of field would be the same that is what I'm talking about as far as surface area, The depth of field doesn't change depending on the format, it's the perception of the depth of field the changes... If for example you could see clearly 5 feet in front of the man and 5 feet behind the man and that was the only distance that was visible clearly, a total of 10 feet, within the 35mm frame it appears as if almost the entire image is in focus, and only slightly may be in the corner behind him you could see the edge of a mountain that would be may be slightly out of focus, but with the large-format image you see more area, so your perception is that the depth of field is much smaller given that you're looking at much more information within the image, when actually both depth of field are the same within both images, a total of 10 feet... However within the 35mm frame we are only seeing just outside of 10 feet, where with the 4 x 5 image we are seeing much much more information and much much larger field of view and so our perception of the depth of field is that it is smaller in comparison to what we can see but the depth of field itself does not change, it will always be 10 feet (in this given hypothetical example...).

    Does this help or make you more confused?
    DOF is very complicated. The COC for 35mm is approximately .03mm, while for 4x5 it's approximately .1mm, while 6x7 MF runs about .06. Given that the same image on each format requires a different focal length to get the same image, the DOF on each would be quite different. Also resolving power limits COC. It can get quite complicated. You can use a 35mm film COC when shooting 4x5 and run the math, adjusting your focus accordingly. Therefore, DOF changes with format, focal length, and distance from the lens to the subject. Of course, when referring to DOF, it's in relation to the focal plan, not the image plane. With 35mm or MF, your focal plane is generally parallel with your image plane. With movements it changes things, as not everything is on the same plane.

    Given the same focal length in both, as you showed, the DOF would still be different due to COC and lens resolution. With a 100mm lens at 10 feet, your DOF on 35mm is a total of 2.89 ft, on 4x5 it's 12.1 feet, and on 6x7 MF it's 6.15 feet. The hyperfocal distance on 4x5 is 20.8 feet and on 35mm it's 68.7 feet. These numbers come from the http://www.dofmaster.com/dofjs.html website. A great resource, the linked calculator shows it all. Wikipedia has a great breakdown of the formulae, as well.
    Last edited by kintatsu; 12-24-2013 at 05:10 AM. Click to view previous post history. Reason: focal plane

  2. #182
    kintatsu's Avatar
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    Quote Originally Posted by analoguey View Post
    You could do the following - 'guesstimate' with your digital and then roll 2 or 3 stops forward or backward depending on what you want to achieve -restricting your shutter speed under 400 or 320 as the larger format goes... Then again, nothing beats experience and taking notes. :-)...
    I try, with digital. But with my large format, I like to be as accurate as possible. It's easier to have the reference for later when printing or talking about the shot. It also helps for when my daughter starts getting more involved in what we do. I also agree about notes and experience. Nothing beats that combination.

  3. #183
    markbarendt's Avatar
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    Quote Originally Posted by StoneNYC View Post
    If you look at this image, you have a larger frame 4x5 which encompasses both a mountain and the river and a person on the mountain, we also have a smaller square which represents a 35mm image of just the person and maybe a little bit of the mountain in the corner of the frame.
    The characteristic you describe is real. In fact it is said of medium format (paraphrased here) that there is a great headshot in every 1/2 length or head and shoulders portrait; that headshot (like the crop the 35mm sized box in your drawing shows) is simply cropped from the original composition. Similarly if we were using 4x5 we may be able to shoot a nice full length portrait and crop out that same great headshot.

    Switching film formats behind a given lens at a given aperture, at given distance from the film simply changes the crop (the crop is the composition/the portion taken from the entire scene in front of the camera that ends up printed on the paper), the effect on the print is essentially the same as if we crop after the fact using an enlarger (or crop a scan) to print from 4x5 negative.

    There is no change in the DOF when we crop within these constraints but the subject matter changes so completely, and the importance (finished/printed size) of each subject within the scene (mountain, sky, trees, people, faces) changes so markedly, that IMO the cropping you describe creates a completely new and different photo; a completely different work of art designed to suit a different audience or intent. Using your drawing as a base just visualize moving your 35mm box an inch and a half in any direction, at that point there isn't even any overlap in content from your original 35mm crop. (Your drawing is fine and fit for purpose BTW)

    This is a fun and important theoretical concept to understand but it's application has significant limits, most notably is if we are trying to shoot to get to a print of a "given" composition.

    When I go out to shoot a full length environmental portrait, that is what I want and what I plan for; cropping a headshot out later doesn't need to be considered when I plan that shot, it just happens to be there. I choose my tools, like most, first to suit the geometry required to get the planned composition; the angle of view from my chosen camera position defines the optimal focal length for a given composition, not DOF. Once I have the focal length figured out, only then can I choose the aperture to get the DOF I want.

    Also, the aperture is limited by the physical size of the lenses that can be mounted on a camera and supported comfortably.

    It would be really tough for example to get 150mm f/2 lens to mount on any 4x5 field camera. The physical aperture size (f=150 so f/2=150/2=75/1) would be 75mm, divide that by 25.4 to get inches and you have a lens roughly 3" inside diameter. Need a pretty big lens board to put that in, and the weight would be considerable, much bigger and heavier than the cameras I own could handle. You might need some really deep pockets to get one built too.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  4. #184

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    Quote Originally Posted by kintatsu View Post
    Basically this is true. Although, different shutter speeds are used on different camera/shutter combinations. On one camera I have (or used to, can't remember.), the shutter speeds include 1/50, 1/25, 1/15, 1/10. We all know time is universal, and thanks to the power of math and standards, so are f/stops, now. It wasn't always the case though.

    My comment there was mostly referring to the fact that I don't shoot without a meter. I need a meter to at least determine a basic luminance. Another aspect of this is that, as many can attest, not all shutters operate correctly. Many lag or lead the listed speed by a certain amount. If you noticed, I also said I use a small range of exposures. The exposure has nothing to do with format.
    Gotcha,

    Well before meters existed photographers used a system that basically works in most conditions

    The basic and most fundamental rule is the sunny 16 rule, where on a bright sunny day you should set that f-stop to f/16 and you match your shutter speed to the film speed (example an ASA100 film shutter should be 1/100 (or 1/125 is probably fine) and in the shade (but still bright day, it's f/11 and an overcast day is f/11 and heavy shade is f/8.

    Once you know these values you can guesstimate fairly well in all outside conditions what exposure to choose, and then you can extrapolate those into other combinations of shutter speed/aperture amounts.

    Get it?

  5. #185

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    Quote Originally Posted by kintatsu View Post
    I try, with digital. But with my large format, I like to be as accurate as possible.
    If you want accuracy, digital is your man. If you want to spend your life trying to achieve 'accuracy' with traditional materials, well... John Sexton beat you to the punch.
    'Cows are very fond of being photographed, and, unlike architecture, don't move.' - Oscar Wilde

  6. #186
    markbarendt's Avatar
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    Quote Originally Posted by batwister View Post
    If you want accuracy, digital is your man. If you want to spend your life trying to achieve 'accuracy' with traditional materials, well... John Sexton beat you to the punch.
    No, digital methods are neither more nor less accurate than traditional materials, both can be done to very high levels of accuracy/quality, any real difference in accuracy or quality of result is generally imparted by the photographer in question.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  7. #187

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    Quote Originally Posted by markbarendt View Post
    No, digital methods are neither more nor less accurate than traditional materials, both can be done to very high levels of accuracy/quality, any real difference in accuracy or quality of result is generally imparted by the photographer in question.
    I'll be honest, I'm not completely sure what we're talking about when using the word accuracy in relation to creative photography - what's the target?
    'Cows are very fond of being photographed, and, unlike architecture, don't move.' - Oscar Wilde

  8. #188
    markbarendt's Avatar
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    Quote Originally Posted by batwister View Post
    I'll be honest, I'm not completely sure what we're talking about when using the word accuracy in relation to creative photography - what's the target?
    That is a good question.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  9. #189
    Sirius Glass's Avatar
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    Warning!! Handling a Hasselblad can be harmful to your financial well being!

    Nothing beats a great piece of glass!

    I leave the digital work for the urologists and proctologists.

  10. #190
    Chris Lange's Avatar
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    so is photography art?

    I need to know.
    See my work at my website CHRISTOPHER LANGE PHOTOGRAPHY

    or my snaps at my blog MINIMUM DENSITY
    --
    If you don't have it, then you don't have it.



 

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