Chroma - Lasercut Acrylic 4x5 Field Camera

StephenM

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I suppose I might as well add a missing advantage to plates over film. They are rigid, meaning that film flatness is a given; there is no possibility of the emulsion surface bowing in towards the lens. If depth of focus is a potential issue (as with wide angle lenses) this could possibly result in sharper images.
 
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I suppose I might as well add a missing advantage to plates over film. They are rigid, meaning that film flatness is a given; there is no possibility of the emulsion surface bowing in towards the lens. If depth of focus is a potential issue (as with wide angle lenses) this could possibly result in sharper images.
Both points interesting, Stephen. I'm just a little confused, though. Is flatness of film an issue? I thought the film holders/DDS had the film pretty well confined on all four sides, and even Fomapan 100 (which apparently has a curly reputation in other formats) seems remarkably flat in its 4x5 polyester configuration. I haven't used any other film yet, though.

On the second point, in 35mm (my normal area of comfort), wider lenses seem to produce a greater depth of field. Is there something I should understand to change this in 4x5? (Although again not an issue for me as I only have one 135mm lens.)
 

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Film flatness is a theoretical advantage - at least, in my limited experience. It may be more of a problem with the larger film sizes that used to be used than the miniature 5x4 of my experience.


On the second point, in 35mm (my normal area of comfort), wider lenses seem to produce a greater depth of field. Is there something I should understand to change this in 4x5? (Although again not an issue for me as I only have one 135mm lens.)
It's more of an issue with longer focal lengths.

Steve.
True; short focal length lenses do have more depth of field. But I said

If depth of focus is a potential issue (as with wide angle lenses) this could possibly result in sharper images.
Depth of field is how much the subject can move and still look sharp; depth of focus is how much the film can move and still record an image that looks sharp.
 
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I originally put some additional text in the post above, and then removed it after a few minutes as being less clear than I would like. I'll now add as an afterthought the following extract from the Walker Cameras site:

The Walker Titan XL 4x5 Field camera is primarily a wide angled camera with a fixed back which addresses the inevitable problem that afflicts all view cameras when used with extreme wide angle lenses, namely parallelism of the front and rear standards; critical depth of focus declines as focal length diminishes as does the need for swings and tilts.
 
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Extreme wide angle large format cameras are usually made in some sort of fixed cone or box form with helical rather than bellows focus with only a rise and fall or cross slide.

Flatness of the film was a real issue with aerial photography as the film could be sucked toward the lens with a bellows camera.
Rollies were sometimes issued with a glass front pressure plate to sandwich the film, to prevent this. I had two with this feature, when not needed it was kept in a pouch built into the case.
depth of focus is less critical with short lenses when doing extreme macro work. as the film to lens distance can be longer than the lens to subject distance.
 

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the film could be sucked toward the lens with a bellows camera.
This is the reason why some people who shoot old folding bellows cameras wait until they actually want to expose a frame before advancing the film.

If the film is already advanced to the next unexposed frame, it can be sucked towards the lens when the camera is opened and the bellows extended, thus potentially bowing the film.

I'm talking more about 120 / 620 roll film folders in this instance but as has been mentioned, it can apply to other formats including sheet film.
 
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True; short focal length lenses do have more depth of field. But I said

Depth of field is how much the subject can move and still look sharp; depth of focus is how much the film can move and still record an image that looks sharp.
I think wide lenses have more tolerance to film position. I made a 6x12 camera with a 65mm Super Angulon. It has a focusing helical, but doesn't really need one. When I accidentally took a shot with it focused to eight feet, I couldn't tell the difference between that and one focused at infinity. That's a difference of about 6mm in lens to film distance.


Steve.
 

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You seem to still be talking about the subject to camera distance...

We'll have to agree to differ on this, as I still believe that there's a difference between depth of field and depth of focus.
 
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Absolutely.. except in macro work, film to lens depth of focus, is always shallower than lens to subject depth of field. Surprisingly monorails and technical cameras are often set up with remarkably poor parallalism. And when using them, exact movements are not that critical, and are usually done by eye.
I have spent hours zeroing the set up of lage monorails, and it has made little difference to the images produced. But it does make you feel happier to have it right, for a while at least.
 
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You seem to still be talking about the subject to camera distance...

We'll have to agree to differ on this, as I still believe that there's a difference between depth of field and depth of focus.
I was trying to work this out in my head and came up with this... A wide lens has good depth of field (range of subject distances), ie it compresses a large range of distances into a small range of distances at the film plane. Conversely, a relatively small movement at the film plane would be equivalent to a large movement of the subject.

Well, it makes sense to me!

(But probably the wrong thread to discuss this...)
 

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Probably the simplest way to think of it is pictorially. As I can't draw easily with letters, try sketching this on a piece of paper.

Draw a couple of curved lines to represent a lens, sketch in the parallel rays (from infinity) on one side, and the converging-to-a-point lines on the other side to the plane of focus. Now consider the angle made by the lines you've just drawn that converge. As you increase the distance to the plane of focus, that angle will become smaller - this, since we're focused on infinity, represents the focal length length increasing.

Now, depth of field depends on our eyes interpreting a circle as a point, which always happens if the circle is small enough. From consideration of the diagram(s) you've just drawn, you can see that this circle increases much more rapidly with distance when the angle is large (i.e. a shorter focal length, usually referred to as a wide angle lens). And conversely, the longer the focal length, the further away you can go from the plane of focus before the circle becomes as large as the one from a shorter focal length.

Q.E.D. (or something).

Edit to add: do we need a new thread "The advantages of plates - or why we should ditch film"?:D

DOF2.jpg

This diagram doesn't show rays from infinity, but it should still make the point clear.
 
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As far as I know, I don’t think anyone else has an (unofficial!) KanYe Edition mirrored gold and white large format field camera

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I built this special edition for Sam Cornwell (Solarcan Sam) as a thanks for his advice and support throughout my Kickstarter campaign. He’s certainly going to find a love/hate response
 

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I’ve now got a printed double dry-plate (and sheet film) holder ready to test.

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I’ve fitted it into a Chroma back with no issues, using either the spring back or the Graflok plates, which means it should work on pretty much any other camera too. I’ve fitted a polypropylene spring plate to each side of the holder and used bookbinding tape to hinge the bottom pieces (like a traditional film holder) to allow the plates to be inserted/removed. Just waiting for my material to arrive to cut the darkslides before I send it over to Jason Lane (Pictoriographica) to test it out with some ‘live’ plates :0)
 
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It's been on the 'to do" list for a long time, but I finally got chance to sit down and write a userguide for the Chroma last night. I finished it at 1am this morning, so still need to check for any typos!, but if anyone gets the chance to have a read over it I'd appreciate any comments/feedback before I share it elsewhere.

https://www.dropbox.com/s/xp7xvnq6yv83cev/Welcome to the Chroma Family.docx?dl=0

It's a 22 page Haynes-esque manual as I've tried to cover all bases!

Cheers
Steve
 

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It's a 22 page Haynes-esque manual as I've tried to cover all bases!
I've only very quickly skipped through the pages Steve so can't comment on the possibilities of typos, however it looks to be well presented and will, I suspect, be very helpfull to Chroma users, myself included!(y)
 

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I'm now on page 8 and without a notebook. So far, at least one typo, a few places where I have stylistic queries, one query on a change of font size and one place where either I don't understand it or it may but wrong! I'll return when I can make notes as I read :D
 
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Hi Steve - firstly it seems very well written and certainly will be very useful to new Chroma users (including me)!

I've read through it all and have very few comments, so will put them here rather than commenting the doc and resending to you:

Page 2, line 1
"its'" shouldn't have the apostrophe - just "its"

Page 14, line 14
"the same one that secure" - secure should be secures

Page 19, end of 1st paragraph
It might be worth mentioning that after tripping the shutter, to remember to replace the darkslide before beginning the process of removing the DDS holder (only because several Chroma users will be new to LF photography)

Page 22, line 3
"ready to packed" should be "ready to be packed"

Cheers,

Conrad.

P.S. Reading through this has made me even more impatient waiting for my Chroma! :)
 

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Page 2 line 1 is probably the typo I spotted.

About to go out; have a broken computer to fix, an article to write for an impending deadline and a holiday to arrange. Plus replying to some important email(s). I will be back...
 
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Hi Steve - firstly it seems very well written and certainly will be very useful to new Chroma users (including me)!

I've read through it all and have very few comments, so will put them here rather than commenting the doc and resending to you:

Page 2, line 1
"its'" shouldn't have the apostrophe - just "its"

Page 14, line 14
"the same one that secure" - secure should be secures

Page 19, end of 1st paragraph
It might be worth mentioning that after tripping the shutter, to remember to replace the darkslide before beginning the process of removing the DDS holder (only because several Chroma users will be new to LF photography)

Page 22, line 3
"ready to packed" should be "ready to be packed"

Cheers,

Conrad.

P.S. Reading through this has made me even more impatient waiting for my Chroma! :)
Thanks a lot Conrad, I’ll go through the doc this morning and update it. I’ll then get back on with building Chroma’s ;0)
 
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Another update on my holders;

- Dry plate/sheet film holder is now ready for testing. I’m sending this one over to Jason Lane so he can expose some plates with it. He’s just finished developing his 25iso plates too so is going to try those.

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This is fitted into the Chroma using the Graflok plates here but also fits under the spring back.

- Wet plate holder is almost ready for testing. I’ve got to cut another version today as I’ve lengthened it by 15mm to make it easier to grip when removing from the camera.

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Final design is 11mm thick so fits easily under a spring back and also works with Graflok plates (as it is here) :0)
 
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Quick update on the holders. We're still testing both the moulded 4x5 plate/sheet holder (currently 3D printed) and acrylic holders to compare pros/cons of each. At the same time I've been drawing up the acrylic 8x10 double plate/sheet holder along with an 8x10 reducing frame to allow the use of 4x5 sheets/plates in any 8x10 camera, without needing a dedicated reducing back.

Acrylic Plate Holders.jpg

Left to right shows the 8x10 holder, 8x10 reducing frame and 4x5 holder. Next job is to draw up the 5x7 holder and equivalent 8x10 reducing frame. The 4 orange tabs on the 8x10 reducing frame are Graflok plates that secure the 4x5 holder into the frame.

The 8x10 holder is 19mm thick, the 8x10 reducing frame is 18mm thick and the 4x5 holder is 16mm thick. They will take both glass plates and sheet film (using a slot in adaptor plate).
 
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that looks ace, what number is that one mate? how many more for the 1st order to be fulfilled-just being nosey:LOL:
Thanks bud. That's the 46th Chroma I've built/shipped. I've got the last few "Kickstarter Specials" to build then I've completed the first three 'early' batches from the campaign and can get on with the Release Editions.
 
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Thanks bud. That's the 46th Chroma I've built/shipped. I've got the last few "Kickstarter Specials" to build then I've completed the first three 'early' batches from the campaign and can get on with the Release Editions.
edit: good on you, they do look amazing. just looked @ kickstarter 112 to go then:cool::eek: be a while till open sales then i take it
 
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