Then do pinhole. Look at this site. http://www.mrpinhole.com/
Then do pinhole. Look at this site. http://www.mrpinhole.com/
Tin Can
What lenses do you have? Five inch (125mm) will focus at infinity at five inches of blows extension, and will provide a 1:1 representation of an object at twice that distance (ten inches or 250mm). Do you have a ground glass?
I`m really embarrassed because I don`t know math or any of the figures on the charts.
The lens`s I have are like the one I used in the box camera, 35 mm I think, their out in the shop so can`t see now.
The lens is about 1/14 inch in diameter.
I just made a glass . it looks to me that I`ll have to have the glass the same distance from the lens as I do with the box camera I made, about 8 inches.
Does the distance that the subject is from the lens make a difference on the image circle?
Here`s the link to my box camera with pictures of some of the lenses I have.
http://http://www.largeformatphotogr...ade-box-camera
G'day Len,
Good to see you've found yourself a new photographic project.
I'm not super at the maths either but as mentioned above, 5" lens focused at infinity needs 5" between lens and film plane. Put an object 5" (or maybe it's 10"?) in front of that 5" lens and to focus it you'll need 10" between lens and film plane. The object will be life size on the film. So closer you focus, the more bellows required.
Now what I think you need to think about is how much does your super-size bellows compress. Is it going to squash down enough to use a 5" lens at a usable distance (unless you want to do some macro shots, you've got plenty of length for that!). Maybe not.
The other aspect to consider is the Image Circle the lens produces. Someone should be able to tell you what happens when you focus closer than infinity, I don't know.
Maybe dig around where you found the bellows, there might be a big old brass lens lurking to be discovered which would be more suitable for your contraption!
Cheers, Nige
Thanks Nige, I don`t get what infinity is, that seems to me to mean any distance to the end of the universe or something.
No big lens to be had but I do have a magnifying glass that is three inch in diameter.
To me a big lens would make a big image and the further I extend the bellows looses the focus.
I`m afraid I`ll just have to put what lens`s I have on it and see what focus`s where.
Pitchy, on the first page of your box camera thread you show three lenses. One is brass and has a shutter with fittings for an air bulb release. Can you give us a snap of the writing on that? It looks like it might be for 5x7.
It`s out in the shop so will check it tomorrow, it will work for 5x7 but I`ll have to have the bellows all the way back which kinda defeats the purpose of having long bellows.Originally Posted by Tim Meisburger
I forgot to say that I can get the lens within five inches from the glass.
The focal length of a lens is the distance from the lens to the ground glass when the image is in focus. So with a 135mm the lens will be 135mm from the ground glass when focused on a subject at infinity. In practice, infinity is something at least a few hundred yards away. Clouds work, as do distant buildings or mountains. As subjects get closer to the camera you need to extend the bellows more to get them in focus, so that a subject at eight feet shot with a 135mm lens might require 220mm of bellows extension to focus (in this case the focal length for a subject at eight feet would be 220mm). For convenience lenses are described using their focal length at the standard distance of infinity (far away).
Okay. So what you need is a lens with a longer focal length. At least about 200mm. Since you have 20" of bellows (500mm) you don't want anything longer than that, and actually you want shorter so that you can focus at closer distances than infinity. You might check the focal lengths of your magnifying glasses.
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