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  1. #11

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    The scale with .7 to 2.3 is a magnification scale.
    A general rule of thumb is at 1:1 increase exposure 4X which is two increments of either shutter speed or aperture. At 1:2 the increase is 8X or 3 stops.
    These are just approximations but you will find them to get you right into the ballpark. I just use these values & bracket my exposures.

    The method QG uses is very good, using speed for full stop & aperture for fractions.
    Heavily sedated for your protection.

  2. #12

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    Quote Originally Posted by Rol_Lei Nut View Post
    There's a reason I suggested looking for a table...
    I don't know... i can do 'the drill' on a pocket calculator pretty fast.
    Excluding the input of both extension and focal length, all it takes are 13 keys in a fixed sequence on a standard pocket calculator.


    But yes of course, i have also compiled tables and carry those in my bag.
    But mainly because the 'general' formulae ignore lens asymmetry, and it does make a difference big enough to worry about, and i am not even trying to memorize the relevant data of all of the lenses i might want to use.

  3. #13
    Rol_Lei Nut's Avatar
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    Quote Originally Posted by Q.G. View Post
    I don't know... i can do 'the drill' on a pocket calculator pretty fast.
    Excluding the input of both extension and focal length, all it takes are 13 keys in a fixed sequence on a standard pocket calculator.


    But yes of course, i have also compiled tables and carry those in my bag.
    But mainly because the 'general' formulae ignore lens asymmetry, and it does make a difference big enough to worry about, and i am not even trying to memorize the relevant data of all of the lenses i might want to use.
    I tend to take a more "in the field" approach, meaning I'm unlikely to have a caculator in my bag.

    What I usually do is stick some gaffer's tape alongside the ratio scale (if there's space) and write the exposure compensation values in their proper places. ALso did that in my macro lenses.
    M6, SL, SL2, R5, P6x7, SL3003, SL35-E, F, F2, FM, FE-2, Varex IIa

  4. #14
    Rick A's Avatar
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    Does the lens you are using have a selector switch to set the aperture at auto or manual? If you can select manual, focus, compose, then set the aperture to the f-stop of choice. If you dont have the selector, go ahead and tape the actuating pin down and follow the previous steps.
    Rick A
    Argentum aevum
    BTW: the big kid in my avatar is my hero, my son, who proudly serves us in the Navy. "SALUTE"

  5. #15
    Erik Petersson's Avatar
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    Yes, I will have to tape that pin down on this lens.

    I did not have a chance to do my photos today as I was not feeling well. Hopefully next weekend will be sunny as well.

  6. #16
    Erik Petersson's Avatar
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    Your posts encouraged me to acquire a bellows unit to my Nikon system. I got it on the mail the other day, and now I am playing around with some lenses before going out to make photos. This is strange: I can only use lenses from 35mm and up. The 28, the 24 and the 20 will not focus when attached on the bellows. Only blur. I wanted to use them to get some more depth of field, but it seems impossible. Can something be done, such as mounting the lens backwards or so?

  7. #17

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    Mounting them backwards could work, yes.
    The problem with retrofocus lenses is that the principal plane can lie too far behind the front lens surface, so that subjects need to be inside the lens for a sharp image to be formed given the lens to film distance created by the bellows. And that obviously won't work.

    Depth of field depends on magnification and aperture. Not on focal length.
    So there is no need to try shorter lenses: you will not get an increase in depth of field at all.

    Depth of field is very small anyway.
    Effort put into getting more of it (by stopping down the lens - the only thing you can do) will not produce significantly more. That is: stopping down far enough may double or quadruple DoF, but it then still is minute, compared to the size of your subject. And image degradation due to diffraction will ruin the resolution inside what little DoF you have long before the little bit extra DoF will become apparent.
    So its better to make do with the little DoF there is and concentrate on how to use that to best effect, instead of spending time and energy chasing after what you will not get anyway.

    Welcome to the world of tiny things!

  8. #18
    Erik Petersson's Avatar
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    As depth of field is not achievable on these small scales, I will have to do without then. Thanks for explaining!

    My idea is to catch a small weed just as it is leaving the soil, so I will have to think of a way to keep the camera clean as well...

  9. #19

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    Cheap clear plastic bags.
    Put them around everything, cutting or tearing holes where there need be.
    And a rag to wipe everything clean afterwards.

    Some shots are best set up in a controled setting. Perhaps your emerging seedling shot would be too: if in a container, you could set that on a support in front of the lens, without you having to lie on your belly with you and the camera pressed down in dirt or even mud. The background will be blurred beyond recognition, so you can put such a set up anywhere where you can find a good background (substitute). You could also create a black background by clever lighting and using black card or paper.

  10. #20
    Erik Petersson's Avatar
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    Another question before I go. This leaves me with a 100mm and a 50mm. The 100mm focus further away from the camera than the 50mm, which is practical. Is there anything else to think of when choosing lenses?

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