Handheld 5X7 thoughts

**Randy** · 16-Jun-2013, 15:41

Christoph, for my 115mm mounted on my 5X7 camera with bellows I think I measured about 18mm travel needed from infinity to 1 meter, but I may be mis remembering

I will try your formula but being bad a math you may have to help me.
I have a helical coming that I got on eBay. It has 28mm of travel, more than I need. Will keep y'all posted as I screw this project up.

**cgrab** · 17-Jun-2013, 14:53

According to my formula, which is unfortunately not mine, but something which I have picked up somewhere (and it might even be this forum), extension for a 115mm lens would be 13,225 mm. With 28 mm of travel, it should be good for a 165mm lens. I must avow that I have not corroborated the formula by taking measurements as I should have, but I estimate my limited experiences to be close enough. I would be grateful if some precision-minded person would take a caliper to his camera and check this out.

**Randy** · 17-Jun-2013, 16:26

I used your calculations and I believe you are correct. That's the good news. Now for the bad - my helical focuser just arrived from Hong Kong and I did not pay close enough attention to the measurements provided by the seller in the ebay listing...the rear cell of my 115mm will not fit up inside the back of the focuser. $160 shot. Back to the drawring board.

**Carsten Wolff** · 10-Jul-2013, 20:16

Originally Posted by Randy

I used your calculations and I believe you are correct. That's the good news. Now for the bad - my helical focuser just arrived from Hong Kong and I did not pay close enough attention to the measurements provided by the seller in the ebay listing...the rear cell of my 115mm will not fit up inside the back of the focuser. $160 shot. Back to the drawing board.

- If you shortened the helicoid a bit, would you be able to fit the rear cell? Any local fitter would be able to put that on a lathe for you and shorten it, for a carton of beer, or reasonable money, I bet, but it may of course be just too wide, or the helicoid not suitable to be shortened on a lathe (or milling machine).

(As an aside, I've made two DIY cameras recently: A 6x9cm (w. 58mm Omegaron): I used the helicoid from a focussing teleconverter I had bought for $2(!). The other is actually a 5x7" underwater camera, which I use without a helicoid (75mm w/a, hyperfocal distance (87cm-infinity) at f22, interchangeable with e.g. a 135mm Macro 1:3 @ f22). (The 75mm can make good use of the camera's Scheimpflug provision, but of course we're not talking handheld in that context)

**Drew Bedo** · 21-Jul-2013, 08:34

Weren't the HOBO cameras a DIY type to start with?

**ic-racer** · 21-Jul-2013, 10:57

Originally Posted by Randy

:-) I already have a few decent DSLR's, and since I will be mostly shooting Xray film cut to 5X7, I can afford to screw up a couple sheets.

You know the speed of your film, you know the speed of your lens, you know how slow of a shutter speed you can use, you know how many inches of DOF you will have at your target print size and acceptable CoC size, right? Can you think of any reason why 5x7 hand helds are not already available

If you don't want to do all the calculations, just lift your 5x7 camera off its tripod before each shot and see how they come out. I know in my hands they would be blurry with X-ray film.

**Ramiro Elena** · 16-Aug-2013, 05:48

Hey Randy, how's your project coming along?

I've been wanting to build a plank 5x7. Mine would be fixed focus though (at the moment). I am planning on using a 190mm Velostigmat fixed focused at 19m. I need to figure out how thick the body will need to be yet.