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Thread: explain like I'm 5......... 90mm lenses

  1. #41

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    Re: explain like I'm 5......... 90mm lenses

    Quote Originally Posted by Dan Fromm View Post
    Joseph, optical vignetting (the dread cos^4) afflects all lenses equally. There've been many discussions about when a center filter is necessary. To the extent that there's a consensus, it is that 90 mm is the shortest focal length that can be used on 4x5 without a CF.

    When a 90 mm lens is shot straight ahead, i.e., with no movements, the very corners of the 4x5 frame will be 1.5 stops down from the center. Most photographers find this tolerable.

    Benno, if this drop of is more than you can tolerate -- it will be if you shoot reversal film -- you should be aware that there are no center filters for the small thin inexpensive 90s you asked about. There are CFs for the modern wasp-waisted ones. To learn more, especially about CFs for lenses whose manufacturers never offered CFs, read my article on the French LF forum. http://www.galerie-photo.com/center-...at-lenses.html
    Woah that site has a wealth of information. Thank you! I always found CF really confusing but this is super helpful.

  2. #42

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    Re: explain like I'm 5......... 90mm lenses

    Quote Originally Posted by Alan Klein View Post
    I just got an idea. I have an f/5.6 150mm. I'll turn the aperture down to f/8 while viewing and see how bright it is to help make a decision about my next lens.

    Quote Originally Posted by BennoLF View Post
    Wait but doesn't this not work? f/8 on a 90mm lens is a lesser transmittance than a a f/8 150mm, because the 150mm lens is a narrower FOV.
    Both transmit the same total amount of light but with a smaller angle the 150mm is brighter per any given area. Or at least so the astro shooters tell me. Something about 'clear aperture size'
    https://petapixel.com/2014/01/29/pic...y-photography/ look about 1/3 of the way down.

    Am I talking crazy?

    Yep, you're talkin' real crazy!

    Think about it: if f/8 (or any other f-stop) was different from lens to lens, then you'd not get the same exposure for the same f-stop when you changed lenses.

    The whole idea of f-stops is that is proportional to aperture size so the amount of light transmission is always the same for a given number.

    Example: f/8 on a 90mm lens = 90 8 = 11.25mm. f/8 on a 150mm lens = 150 8 = 18.75mm. The longer lens has a larger aperture at f/8 than the shorter, which lets in more light, which compensates for the smaller field of view.

    For a given aperture size for both lenses, your reasoning is correct. It's just that the f-numbers would then be different.

    Example: A 9mm aperture on a 90mm lens = f/10 (90 9 = 10). That same 9mm aperture on a 150mm lens = f/16.6 (150 9 = 16.666...). The division works both ways.

    Some things can affect transmission, like haze on lenses, reflections from lots of elements, etc., but that's a separate issue from the f-stop.

    Best,

    Doremus

  3. #43
    Alan Klein's Avatar
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    Re: explain like I'm 5......... 90mm lenses

    I plan on shooting chromes down the road in addition to BW. Would that change anyone's opinions on which 90mm lens? (Note that I have all filters in 77mm. So I don't want to go above that filter size)

  4. #44
    Alan Klein's Avatar
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    Re: explain like I'm 5......... 90mm lenses

    ...color chromes and color negatives...

  5. #45
    Corran's Avatar
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    Re: explain like I'm 5......... 90mm lenses

    Pick a lens and go shoot! Don't get bogged down with paralysis by analysis!
    Bryan | Blog | YouTube | Instagram | Portfolio
    All comments and thoughtful critique welcome

  6. #46

    Re: explain like I'm 5......... 90mm lenses

    Quote Originally Posted by Alan Klein View Post
    I plan on shooting chromes down the road in addition to BW. Would that change anyone's opinions on which 90mm lens? (Note that I have all filters in 77mm. So I don't want to go above that filter size)
    I'm currently only doing black and white ( 4x5 TMax 100 and 5x7 Delta 100) on LF and then scanning for digital post-processing and printing.

    That hybrid process allows me a fair degree of digital correction in post-processing and I have a wide-format Epson 7900 printer that can do excellent BW prints if carefully calibrated. That affects my own approach.

    Some of the best aspects of LF photography are that a wide range of options and approaches are open to everyone, that nearly any age, make and model lens can be adapted to a LF camera, and that DYI is feasible for virtually anyone with a modicum of experience. That makes LF quite flexible and allows everyone to find their own approach.

    Chromes are certainly more susceptible to vignetting and more difficult to correct. I cannot comment about shooting LF chromes as I lack personal experience there.

    That said, while some may take a different and possibly idiosyncratic view, IMHO sharpness and contrast are very important optical criteria, although certainly not the only ones, because higher sharpness and crisp contrast usually record the image more faithfully and thus provide more "information" and more accurate information, than lenses that are not as sharp nor exhibiting crisp contrast.

    You'll of course find differing opinions - think 1930s Pictorialists vs. the f/64 revolution by Edward Weston, Ansel Adams, et al. It all depends upon what you want to do and whether you want to achieve a particular result and do so in-camera via a particular lens.

    If you want a softer image, that's possible after the fact IF you start out with enough information in the original image capture, but you can't go the other way and try to extract more information from an image where the underlying information was never captured when the shutter was clicked.

    Older lenses would likely be less suitable for chromes than more modern lenses from Nikon, Schneider, Rodenstock, and Fujinon, all of whose more recent products have excellent reputations.

  7. #47

    Re: explain like I'm 5......... 90mm lenses

    Quote Originally Posted by Dan Fromm View Post
    Joseph, optical vignetting (the dread cos^4) afflects all lenses equally. There've been many discussions about when a center filter is necessary. To the extent that there's a consensus, it is that 90 mm is the shortest focal length that can be used on 4x5 without a CF.

    When a 90 mm lens is shot straight ahead, i.e., with no movements, the very corners of the 4x5 frame will be 1.5 stops down from the center. Most photographers find this tolerable.

    Benno, if this drop of is more than you can tolerate -- it will be if you shoot reversal film -- you should be aware that there are no center filters for the small thin inexpensive 90s you asked about. There are CFs for the modern wasp-waisted ones. To learn more, especially about CFs for lenses whose manufacturers never offered CFs, read my article on the French LF forum. http://www.galerie-photo.com/center-...at-lenses.html
    Hi, Dan: Thanks for the information about the 1.5 stop vignetting - I forgot the formula. As I shoot only BW at this time on LF and then scan, post-process, and digitally print, I haven't been bothered by the vignetting due to my own style but I can certainly see how it would be a concern when shooting chromes as per the OP.

  8. #48
    Peter De Smidt's Avatar
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    Re: explain like I'm 5......... 90mm lenses

    Quote Originally Posted by Corran View Post
    Pick a lens and go shoot! Don't get bogged down with paralysis by analysis!
    Yes!
    May tomorrow be a better day.

  9. #49

    Re: explain like I'm 5......... 90mm lenses

    Quote Originally Posted by Bernice Loui View Post
    What were the "test" methods used to determine the SW Nikkor 90mm f8 was the "sharpest" of the lot?

    *Camera used, film used, how was the film processed, subject & lighting conditions used, criteria used, how many representative sample(s) of SW Nikkor 90mm f8 lenses were tested......

    It is more likely the 90mm f8 SW Nikkor had higher contrast not "sharper" than the others. This combined with a very long list of possibilities plus cognitive bias, image rendition bias and LOTs more all figure into that assertion of "sharper".

    As for Fujinon LF lenses being "Superior" again, the is completely subjective and dependent on the needs of image maker and print goals.

    Higher contrast is not "sharper"... In many real world sheet film to print image making realities, the sharpest lens is NOT the best lens for a given print. It is a LOT more complex than optical performance of any given lens.

    As for which wide 90mm for 4x5 or 5x7_13x18cm, what is the print's goal? As previous mentioned and many times before, there are NO ideal lenses for ALL print goals. Go directly back to the intent and goal of the finished print, then figure out what lens-camera-lighting-film-post processing is required to achieve that print.


    Bernice
    Hello, Bernice:

    FWIW, although I have mentioned that modern Fujinon lenses have proven to be reliably good for me and relatively more affordable used, I am not a Fujinon evangelist as I also use multiple modern lenses from Schneider, Nikkor, and Rodenstock. That said, the Fujinons and Rodenstocks have, for me, been the most consistently good optically.

    I certainly understand your thoughts about the look of a certain lens as I also shoot regularly with eight classic lenses, four Zeiss Protar VIIa, a Voightlander 115mm Ultragon, and three Dagor lenses, and keep an appropriate one in every one of my large format kits from 4x5 through the 11x14 outfit. Some of these are as good as the better modern lenses and some less so.

  10. #50

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    Re: explain like I'm 5......... 90mm lenses

    Quote Originally Posted by Doremus Scudder View Post
    Yep, you're talkin' real crazy!

    Think about it: if f/8 (or any other f-stop) was different from lens to lens, then you'd not get the same exposure for the same f-stop when you changed lenses.

    The whole idea of f-stops is that is proportional to aperture size so the amount of light transmission is always the same for a given number.

    Example: f/8 on a 90mm lens = 90 8 = 11.25mm. f/8 on a 150mm lens = 150 8 = 18.75mm. The longer lens has a larger aperture at f/8 than the shorter, which lets in more light, which compensates for the smaller field of view.

    For a given aperture size for both lenses, your reasoning is correct. It's just that the f-numbers would then be different.

    Example: A 9mm aperture on a 90mm lens = f/10 (90 9 = 10). That same 9mm aperture on a 150mm lens = f/16.6 (150 9 = 16.666...). The division works both ways.

    Some things can affect transmission, like haze on lenses, reflections from lots of elements, etc., but that's a separate issue from the f-stop.

    Best,

    Doremus
    Wait now I'm further confused lol.

    f/8 for any two different focal lengths is the same light input total. Isn't it kinda like slow, wide river or fast, narrow river?
    A 3000000mm f/8 is picking up light from like .0005 degrees, so to get a balanced exposure it needs to pick up a HECK ton of light/degree.
    A 30mm f/8 is picking up light from like a jillion degrees, so it's a much lower level of light/degree.

    If you have a totally dark room with one lightbulb in it, metering a 'correct' exposure at f/8 will yield two different shutter speeds for two different focal lengths. Right?
    The wider lens needs a longer shutter speed because it's viewing more darkness, so the lightbulb takes up a lower percentage of the exposure.
    The tighter lens can have a faster shutter speed because it's just looking at a lightbulb.

    This is all based on a metering system looking for an average of zone V.

    I feel even crazier now but there's something in my mind that doesn't click.

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