1. AshleyC

    AshleyC

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    Anyone know of a review site for LF lenses? I've a hankering to treat my Wista to a new lens since I haven't bought one for it since they day I picked it up, but know absolutely nothing about the quality of lenses out there.
     
  2. Woodsy

    Woodsy POTY Winner 2009

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    Though not a *review site* as such, Kerry Thalmann is a good start; particularly his future classics list. I bought my Schneider Super Symmar 120mm HM lens on his (and backed up by many other) recommendation, and it's been completely worth it. I also started my justification for my recent purchase of a Fujinon A 300mm lens from his site.

    http://www.thalmann.com/largeformat/

    Best thing really to do is decide on what focal length you're after and then see what reviews say from there about the various offerings.
     
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  3. StephenM

    StephenM

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    I may have - but what size board? IF I have one, it's probably Wista fit; although I might have a Canham one as well,

    NB. I'm in Callandar as I type this, and may not have internet access again until next week.
     
  4. Kevin Allan

    Kevin Allan

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    If rain stops play, try the second-hand bookshop on the main street.
     
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  5. Woodsy

    Woodsy POTY Winner 2009

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    A linhof / wista / etc style one is the type I need, in copal 1 :)

    If you do have one for sale, how much are you looking for?
     
  6. StephenM

    StephenM

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    Sorry - back home now and I've checked the case with the boards. I have 2 Wista Copal 0 boards but the Copal 1 board is a Toyo/Canham one.
     
  7. StephenM

    StephenM

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    Wet; visited; two books bought :)
     
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  8. Woodsy

    Woodsy POTY Winner 2009

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    Not to worry, many thanks for looking :)

    Anyone else have a spare linhof copal 1 lens board?
     
  9. Andysnap

    Andysnap POTY (Film) 2015

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    Sorry mate, my spare one is also copal 0. :(
     
  10. Woodsy

    Woodsy POTY Winner 2009

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    Might be a daft question, but does anyone have a schematic diagram of a lens board with dimensions? Might be able to get one made at work...
     
  11. StephenM

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  12. stevelmx5

    stevelmx5

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    What's the outside diameter of your existing lens board and how thick is it? Copal #1 is just a 41.6mm hole. I've got 2/3/5mm Acrylic here so could draw one up for you and laser cut it later this week when I go down to do my camera.
     
  13. Woodsy

    Woodsy POTY Winner 2009

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    Very kind of you to offer matey! Might you be able to send me the part number of the 2mm acrylic? I'm concerned about the optical properties is all :)
     
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  14. stevelmx5

    stevelmx5

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    I can send you the optical properties of the black vinyl sheet that will be stuck to the back of the board if you like ;0)
     
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  15. eeyore

    eeyore

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    One the intrepid 8x10 vibe... How will people be developing 8x10 film?
    Seen a few options..
    There is a kickstarter for a tank, catlabs have a MOD45 type holder (ebay), there what look like mini pipe bombs for single sheets (ebay) or do you use tube or rings to hold them in a big patterson tank?
     
  16. Carl Hall

    Carl Hall

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    I think if I were to invest in an 8x10 system then I would just tray develop in a dark room. I can't see trying to unload 8x10 sheets in a dark tent going well!
     
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  17. eeyore

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    I did consider this but the problem with that sort of route I don't really have space, not even sure I could have a dark tent to put up and down
    That and my clumsy hooves would be a disaster waiting to happen! :exit:
     
  18. StephenM

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    On developing 10x8, I have a number of options.

    1. Use a Paterson orbital processor which I have. Disadvantage - I'd prefer not to have continual agitation.

    2. Buy a 10x8 tank from Stearman when they become available.

    3. Buy an open tank and hangers and use my darkroom (possibly adding in a pair of IR glasses which were recommended on another forum to let you see in the dark without fogging film). Or use ortho film (I'm black and white anyway) and a suitable safelight (I have one already).

    4. Tray development with IR goggles - I have plenty of developing dishes.
     
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  19. Andysnap

    Andysnap POTY (Film) 2015

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    Just thought I would say, and I fully understand that most people are fed up with my inner LF wranglings, that this weekend on at least 3 occasions, I thought 'I wish I'd brought my Wista '. Basically I'm keeping the lf kit. :D
     
  20. Woodsy

    Woodsy POTY Winner 2009

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    Good on you mate :) Perhaps treat it as the backup camera. Get the shots you want on the cheaper-per-photo cameras, then get yourself a stress free 'backup' on the Wista?
     
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  21. Carl Hall

    Carl Hall

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    For those large formaters that do close up work, what's your method of calculating bellows extension factors? I have an idea for a photo that I'd like to take (*cough* FPOTY *cough*) on the 4x5 and I've not used it up close before.

    From what I've read it's (1+M) where M is the magnification factor. So say I'm taking a photo of an apple, which is 75% of the size on the ground glass as in real life 1+0.75 = 1.75 (which I calculate as about 68% of a stop ?) So my 5 second exposure becomes around 8.5 seconds.

    Then adding reciprocity for FP4, that 8.5 seconds becomes somewhere around 25 seconds (I say "somewhere" because Ilford's reciprocity charts are uselss).

    So my metered 5 second exposure would be 25 seconds.

    Have I got this more or less right? I've not considered bellows factors before!
     
  22. steveo_mcg

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    I've limited experience with bellows factors, I could never work out the chart on the RB. 25 seconds is about right for a 5s exposure on FP4 though.
     
  23. ChrisR

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    Bearing in mind I know NOTHING about this... I presume the "bellows factor" comes in to play because there is a significant extension beyond the focal length, that changes the effective aperture. In a conventional camera a 50mm f/2 lens would have an aperture diameter of 25mm. The movement of the lens to focus will affect this, but not enough to count. But if you have, say, a 200mm lens at f/8, the aperture is also 25mm... then if you extend the lens by a lot in order to focus much closer, then that 25mm aperture becomes effectively smaller. If it extended to 250mm from the film plane in order to focus on the closer object, then the aperture is effectively f/10, near enough to a full stop smaller. I can't at this minute do the maths to relate this to magnification factors....

    ... and I expect someone will come along in a minute and explain why I'm wrong!
     
  24. Kevin Allan

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    Bearing in my mind I only took my first large format image half an hour ago (my Intrepid camera is here), but the method I have used is the calculator at this site:

    http://www.cookseytalbottgallery.com/photo_blog_article.php?blRecordNumber=24

    There's an online calculator with a link near the top of the page, and further down a link to a printable ruler.

    In simple terms you divide the bellows extension by the lens focal length and the result is the number of stops extra to add.

    Eg with 300mm bellows extension and a 150mm lens you would add two stops of exposure.

    The full version is Bellows extension squared / focal length squared but the squares either side cancel each other out so you can ignore them,
     
  25. ChrisR

    ChrisR

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    Well, using my example of 200 mm lens with a 50mm extension, his calculator gives -4 stops, so I guess my idea was wrong! I'm struggling to see the logic behind the Cooksey Talbott formula, though...
     
  26. StephenM

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    I can't copy and paste and still keep the formulae from a word document; but my take on "useful formulae" can be downloaded here (2 page pdf). Pasting has this effect (so if you think it might be helpful, download and you'll see the equations that I can't paste in).

    3. Useful formulae for close up photography

    There are two basic formulae used with lenses:



    [​IMG]

    where f = the focal length

    u = the distance the subject is in front of the lens

    v = the distance of the plane of focus behind the lens.

    Equation 1 Basic lens equation



    Since lenses used in photography are thick lenses with several elements, the actual plane within the lens used for these measurements are the nodal planes, and these won’t be marked for you. But, as we’ll see, this doesn’t matter a great deal. The other basic formula relates the magnification of the subject to the distances in front of and behind the lens:



    [​IMG] where M = the magnification and u and v are as above

    Equation 2 Magnification as a function of subject and image distances



    Using simple algebraic substitutions in these formulae, we can get equations to answer the most common questions in close up photography



    The distance the subject will be in front of the nodal plane of the lens at a given magnification is given by



    [​IMG] When working at 1:1, M = 1 and u = 2f

    When working at 1:2, M = ½ and u = 3f



    Equation 3 Subject distance as a function of magnification

    We saw in chapter 9 that this formula is actually an approximation that works reasonably well until you get really close to the subject, but is increasingly in error after (say) 1:1. The exact formula should substitute [​IMG] for M, where P is the pupil magnification which can be a significant size, as we saw in chapter 9 when we looked at reversing a lens.





    Many lens makers specify the closest focusing distance in terms of distance from the focal plane of the camera, rather than the front of lens; this formula will give you a reasonable idea of what your working distance will really be.



    If you want to calculate more exactly how far in front of the lens the subject will be, or if the camera maker only tells you how far the subject is from the lens and you want to work out what the value of M is (some compact cameras specify the closest focusing distance in this way, and leave you wondering what that means in terms of magnification) then you can use the following formula:

    [​IMG]

    Equation 4 Subject distance as a function of magnification

    If you know the closest focusing distance from the front of the lens, then you also know that if you add the distance from the focal plane to the front of the camera to this distance, the result will be approximately u + v (or exactly if the front and rear nodal planes of the lens coincide) which is

    [​IMG]



    And knowing f, you can work out the magnification.



    Exposure increases when using tubes or bellows can be worked out either from the length of the extra extension E and the focal length of the lens F using the formula



    Exposure increase = [​IMG]

    Equation 5 Exposure increase for a given extension

    Or using the magnification M and the marked aperture f you can calculate the effective aperture F



    [​IMG]

    Equation 6 Effective f stop and magnification
     
  27. StephenM

    StephenM

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    If you're using a large format camera where you can easily put a ruler on the ground glass, if you place an object of known size at the plane of focus and measure the size of the image on the ground glass, you can work out the magnification by simple division. You then add one to this number, and multiply the marked aperture by the result; this gives the effective aperture. As far as I know, this is the only method that doesn't involve squaring quantities (short of marking the camera bed with exposure factors) to allow for extension.

    F (effective aperture) = (1 + Magnification) x f (marked aperture).

    Hence, as everyone knows that 1:1 (M = 1) requires 2 stops extra exposure

    F = 2 x f and hence f/16 gives an effective exposure aperture of f/32 - which in stops is f/16-f/22-f/32 = 2 stops.
     
    Last edited: Jun 22, 2017
  28. ChrisR

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    Thanks Stephen. I couldn't read the formulae in post 1466, but the PDF is interesting. Your formula (equation 5) for exposure increase related to bellows extension is (F+E)**2/f**2 (using a FORTAN-like pseudo notation where **n means raised to the power of n). This makes much more sense than the Cooksey Talbot formula which is E**2/F**2. Your formula is greater than 1 for all positive extensions, while the latter can be less than or greater than 1 depending on whether the extension is less than or greater than the focal length. I was already suspecting last night that the second formula was wrong in this sort of way, perhaps the result of confusing the extension with the extended length..

    Bit of a problem between equations 5 and 6 as in 5 F is focal length, while in 6 F is the effective aperture!

    Applying your equation 5 to my 200 mm lens example, the effective exposure increase would be 1.56, say 2/3 of a stop, not too far from the f/10 from my simple calculation! I couldn't see a way from your formulae of working out the magnification from a given lens extension, though I guess a little bit of work on equations 5 and 6 (with adjusted notation to avoid clashes) would give the right results.
     
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  29. StephenM

    StephenM

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    The basic lens equation relates (for an in focus subject) the subject to lens distance, the lens to sharp image distance and the focal length. With a simple, one element lens, the subject and image distances can be measured from the centre of the lens; with compound lenses they are measured from two different planes which are often within the lens physically. But if we assume that for all practical purposes for exposure, we can assume some arbitrary point on the lens (let's say the lens board position on a LF camera) then we can simply calculate the magnification as the ratio of lens to subject and lens to image distances. Maths on request, but it's simple trigonometry from similar triangles.

    Hence a tape measure can be used with one piece of long division.
     
  30. Andysnap

    Andysnap POTY (Film) 2015

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    :confused::runaway::thinking: What? Who? Where?..... Aaaargh my head hurts.
     
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  31. FruitFlakes

    FruitFlakes

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    Re: Bellows compensation.

    Print this, laminate it, and keep it with your LF kit:

    http://www.salzgeber.at/disc/

    I also use an app (Reciprocity Timer on iOS) as a backup, it calculates bellows compensation, filter comp, and reciprocity. Very useful.
     
  32. StephenM

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    Ah, if you think that's complicated, you should see what happens if you take the equation for depth of field and partially differentiate it to obtain equations for how the depth of field varies with aperture, focal length and focusing distance independently :D

    In practice, I'm more slapdash relying on latitude and simply going for half a stop if I get close, 1 stop for a close up and that's it, as I don't do macro. But given that 2 stops is the maximum you'll probably need and film latitude in black and white (my chosen medium) is pretty good, I get away with it.

    While I'm typing, a thought crossed my mind which is such a rare occurance that it ought to be documented. I said that 2 stops is the maximum. I based this on large format field cameras having limited bellows extension (only 300mm in Wista, I think) which makes 1:1 to maximum for a standard 150mm lens. It's long been one of my hobbyhorses that the sacred "true macro means 1:1" is nonsense, as (for example) a postage stamp fills a 4/3 frame at 1:1 but it takes a dinner plate to fill 10x8 at the same ratio. Does this in effect mean that as format size goes up, so true macro requires much greater extensions than large format camera typically provide? Or do large format photographers simply think big and do macros of large objects rather than small ones?
     
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  33. StephenM

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    Well spotted that man! I've just corrected the offending place to put "f" for "F" in the final equation. This was appendix 3 to my book, by the way.
     
  34. ChrisR

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    Would it not be better to use A and a for aperture in equation 6 instead of F/f? Of course I haven't seen the rest of the text so don't know how this might conflict with other uses of A/a.
     
  35. StephenM

    StephenM

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    Ah, "f" for "fresh" thinking! I was using "f" as enshrined in f numbers for apertures. My only concern would be that everyone and his dog is familar with f and t stops; "a" might be a stop too far. More seriously, I agree that some letters are overworked. And I'll admit that even over 50 years after I first came across the 1/f = 1/u + 1/v I still can't remember which of the u/v pair is the subject distance and which the object distance! I've tended to stick to the terms I grew up with; from memory, some American optics books use different letters to the "u" and "v" I've just quoted.

    You can pick up the 410 page pdf here when you have an idle year or two. (Table of contents at the end, courtesy of Microsoft Word).
     
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  36. Andysnap

    Andysnap POTY (Film) 2015

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    I finally developed my last 2 shots from the Cornwall meet, wish I'd done them earlier as they are the best of a bad bunch. :D

    Wista 45, Nikkor 180mm f5.6 on Fuji 160NS , first one looking out over Porthcothan Bay and the second from just about a mile along the coast.
    [​IMG]Porthcothan1 by Andy, on Flickr

    [​IMG]Near-Porthcothan by Andy, on Flickr
     
  37. ChrisR

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    Two definite successes there, Andy. I took many shots trying to get the sea thrift in sunlight to figure in the foreground of an interesting background, without success. I think you cracked it!
     
  38. Andysnap

    Andysnap POTY (Film) 2015

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    Thanks Chris. I've done a little more tweaking to the second one and I have printed it out at home just to see how it looked. I did use a sheet of Hannemuhle 320gsm rag paper and my very old and cheap Epson printer, but I think it looks pretty good. I may get a larger print done on similar paper.
     
  39. stevelmx5

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    Quick question. Would you choose a Xenar 150mm 4.5 or a Symmar 180mm 5.6 to go alongside an Angulon 90mm?

    As far as I can see, the 180mm has a larger image circle so gives more options for movement but other than that, the results I've seen seem to offer similar quality. Decisions!
     
  40. StephenM

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    From memory - this is a quick answer to a quick question! - the Xenar is a telephoto design, which means it's not so easy to use when you tilt/swing. So I'd go Symmar, especially as (assuming it IS a Symmar not Symmar S etc.) it will be a convertible lens and give you another focal length if you need it.
     
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