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Thread: Image Circle too small?

  1. #1

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    Image Circle too small?

    Hi all, I'm new here and new to LF - so it's all a bit daunting!

    I may have made a boo boo - I've just got a Ebony RSW45 and a second hand Rodenstock 55mm f4.5, I'm now worried that the image circle is too small at 163mm at f22. Is this image circle OK with the 4x5? It's on a recessed board, would it help if it were a non recessed board, will it allow for ny movement or would it be OK at a smaller aperture?

    As I say, I'm new to all this so it's all seeming a bit complicated!

    Oh yeah - Can I not use standard filters with this lens either, as it's so wide angle?

    Thanks for any help

  2. #2
    All metric sizes to 24x30 Ole Tjugen's Avatar
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    Re: Image Circle too small?

    The image circle is enough, but only just.

    The image circle is the same regardless of lens board, but it increases a bit with close subjects. Think of the image circle as a cone projecting out from the back of the lens, with the tip at the aperture. when you focus on something close you rack the lens a little bit further from the film, so the cross section of the "image cone" at the film plane makes a larger circle.

  3. #3

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    Re: Image Circle too small?

    As Ole said, you lens will work, just. However, a lot of the fun of a large format camera is using the movements to create photos that a standard 35mm camera can't get. This requires a lens whose image circle is much larger than the minimum needed for the format. My advice is to get a cheap, longer length lens. Something in the 150 range would be good for your camera. Play with that lens and learn how all the movements work. A really short lens is tough to learn on as they tend to have pretty minimal movements and are hard to focus well. Also, it is hard to compose a really good wide angle image as it gets very cluttered, fast. As an example, when I backpack and take landscape photos, I have 90, 135, 200 and 300mm lenses. The 135 is my most used lens by a lot. I use the 300mm more than the 90. I have a 47mm lens for my Ebony but have never really gotten a good shot with it. Most scenes have too much stuff in them to really work as a photo.
    Good luck,
    Dave B.

  4. #4

    Re: Image Circle too small?

    This most recent post should be of interest.

    http://www.largeformatphotography.in...ad.php?t=27857

  5. #5

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    Re: Image Circle too small?

    Hi. What makes you think the image circle is too small? have you seen results on transparencies/negatives to suggest vignetting? The reason I ask is that I have used the same lens/camera combo and never had a problem. The thing to remember is that the angle of view of the 55mm is wide - the need for any movements is rare. You can, however, employ a few degrees of front tilt without undue concern. I never needed a recessed lens panel either. I did use a 67-77mm step-up ring for filters though.

  6. #6

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    Re: Image Circle too small?

    Thanks for the info everyone, I realise now that getting a 55mm for a first lens wasn't my most successful decision! My reckoning was that I mainly use a 12mm on my dSLR for landscapes so I'd go for something similar. I'll look at getting something that may prove easier to use whilst I'm getting used to the camera.

    Glad to hear you've used the same set up Paul O and it's works fine, I have a Cokin X-pro set up for filters, I wonder if these are usable without vignetting with a slim holder?

  7. #7

    Re: Image Circle too small?

    Paul, this has not been my experience with the lens. I am using a Heliopan 67-77 SUR and with a Singh Ray thin mount filter (4.8mm) I see a bit of vignetting. And forget base tilts of more than 2 degrees (accurately measured on my Arca). Front axial tilts even less. Bob Solomon has recommended that a larger SUR (minium 86mm front) is required to circumvent vignetting.

  8. #8

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    Re: Image Circle too small?

    Quote Originally Posted by Paul O View Post
    Hi. What makes you think the image circle is too small? have you seen results on transparencies/negatives to suggest vignetting? The reason I ask is that I have used the same lens/camera combo and never had a problem. The thing to remember is that the angle of view of the 55mm is wide - the need for any movements is rare. You can, however, employ a few degrees of front tilt without undue concern. I never needed a recessed lens panel either. I did use a 67-77mm step-up ring for filters though.
    If coverage is close you're better off using back tilt than front. Back tilt moves the film within the image circle so you don't need any more coverage with back tilt than you do without it (well a little in some situations but not much). Front tilt moves the image circle itself relative to the film and so requires a larger image circle.
    Brian Ellis
    Before you criticize someone, walk a mile in their shoes. That way when you do criticize them you'll be
    a mile away and you'll have their shoes.

  9. #9

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    Re: Image Circle too small?

    [quote]If coverage is close you're better off using back tilt than front.[quote]

    While this is very true, the Ebony RSW45 is restricted to using front movements.

  10. #10

    Re: Image Circle too small?

    Just to add to Brians suggestion, you can squeek a bit more rear base tilt out if you drop the front standard no more than 5 mm. Remember, with rear base tilt, the top of the image is moving into the image circle where the coverage is somewhat reduced. To correct for any vignetting, dropping the front standard adds a bit more coverage without sacrifice to the bottom of the image (since it is in a larger part of the image circle).

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