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Author Topic: Pinhole photography with Leaf and Phase One backs  (Read 2332 times)
rogerxnz
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« on: October 17, 2012, 02:35:55 PM »
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I have hijacked the thread How does the Dalsa-based backs know the Copal shutter speed? into a discussion about how to turn a Hasselblad 5xx camera into a digital pinhole camera with an Aptus or Credo back and I reckon the new subject deserves more prominence. So, I have copied an edited version of the discussion on pinhole photography here but please see the other thread for the links and images.

My initial query:
I know it [pinhole photography] can be done with a Phase back because they are triggered by the metal "feeler" that comes out of the rear of the body when a shot is taken to ensure the film slide is absent and they have a button you can press to turn the sensor on and off. But a Leaf back is triggered from the flash synch and that won't be present with a pinhole lens attachment.
Roger

Reply from DOUG PETERSON (dep@digitaltransitions.com)


0. Set the back to "large format"
1. Unplug the sync cable from the lens.
2. Take a ballpoint pen and hold it against the contacts of the cable sync cable, while doing this uncover the lens.
3. Prior to releasing the ball point pen recover the lens so the sensor is in darkness when you release the ball point pen.

Alternatively you can use the "old style wakeup cable" from Phase One with the Leaf back. This is part #50300131 on our estore. Same end result, but much easier mechanics (just hold the button down for the length of the shot - the very slight camera shake will be hidden by the utter lack of sharpness of the pinhole camera).

See more medium format pinhole images. http://www.doug-peterson.com/?s=pinhole

Comment from Yair


See also Chris Ireland's article [see the article at http://www.directdigitalimaging.com/article/technical-articles/]
« Last Edit: October 17, 2012, 02:44:27 PM by rogerxnz » Logged

Roger Hayman
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rogerxnz
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« Reply #1 on: October 17, 2012, 02:42:00 PM »
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Now, to continue the discussion, I would like to know how the photographers get away with the long exposures usually required for pinhole photography when the backs have a limit for exposures of one or two minutes?

Chris Ireland uses a Phase One back and mentions exposure times of 1 second up to 9 mins (at f180!).

How can he do that? Wouldn't the sensor have gone into meltdown before it got to 9mins?
Roger
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Roger Hayman
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Doug Peterson
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« Reply #2 on: October 17, 2012, 02:59:19 PM »
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Now, to continue the discussion, I would like to know how the photographers get away with the long exposures usually required for pinhole photography when the backs have a limit for exposures of one or two minutes?

Chris Ireland uses a Phase One back and mentions exposure times of 1 second up to 9 mins (at f180!).

How can he do that? Wouldn't the sensor have gone into meltdown before it got to 9mins?

Phase One IQ180 and Mamiya Leaf Credo are each spec'd for 2 minute max exposures.
Phase One P20+, P21+, P25+, P30+, P45+ are each spec'd for max one hour exposures. Of these the P45+ is generally acknowledged as the king of long exposure amongst all backs, especially at times over 30 minutes.

So 9 minutes is not even breaking a sweat for a P45+.

Given that there is not that much scene detail (cause it's a pinhole, not an uber sharp modern lens) you can safely apply fairly aggressive single-pixel noise reduction and exceed the stated specs by a bit.

My pinhole was a larger-than-normal pinhole and I hand held it at something like ISO800. Probably some camera shake, but I mean, it's a pinhole - I wasn't exactly obsessed with sharpness :-).

These times are:
- at lowest ISO
- at ambient temperatures around 68F (20C). Longer is possible at lower temperatures, less at higher temps.
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FredBGG
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« Reply #3 on: October 17, 2012, 10:27:39 PM »
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Another option is to get an old large format shutter out of the middle of a large format lens.
That way you can just attach your sinc to the flash connector on the shutter.



Just make sure you get one with a b and t setting on the shutter speed. makes long exposures easier.

You can also mount a skink pinhole "lens" on the front.
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HarperPhotos
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« Reply #4 on: October 17, 2012, 10:41:57 PM »
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Now that’s using the old grey matter Fred. Good idea.

Cheers

Simon
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rogerxnz
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« Reply #5 on: October 28, 2012, 02:28:10 PM »
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If you attach a ground glass viewing adapter to the rear of your pinhole camera (similar to the viewfinder arrangement for the Flexbody), can you preview your pinhole shot or is there not enough light?

I'm thinking that turning a Flexbody into a pinhole camera could open up many possibilities but it only be worthwhile if you could preview the effects of the tilt/shift/bellows extension.
Roger
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Roger Hayman
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Stefan.Steib
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« Reply #6 on: October 28, 2012, 02:37:41 PM »
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With an HCam and our electronic timer you can do this 1 hour shots with a P45+ easily.
You caneven set it up  to wait 1 hour and a minute before the next eposure (because this is what you need for the dark calibration)

regards
Stefan
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Graham Welland
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« Reply #7 on: October 28, 2012, 03:51:40 PM »
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Another option is to get an old large format shutter out of the middle of a large format lens.
That way you can just attach your sinc to the flash connector on the shutter.



Just make sure you get one with a b and t setting on the shutter speed. makes long exposures easier.

You can also mount a skink pinhole "lens" on the front.

This is what I did for my Alpa. Rather than buy a new Copal 0 shutter I was able to find and buy a damaged Nikon LF lens for $100 and took the as-new Copal 0 shutter from it. I got the pinhole from Lennox Laser: http://www.lenoxlaser.com/index.php?dispatch=products.view&product_id=122 and then mounted them on a lens board/helicoid for a 47mm lens that I found used on GetDPI.

I use the Copal shutter with my wake up cable to trigger the back with wake up pulse and then keep open using T or B mode. With the P25+ there is no problem with long expsoures. With my IQ160 you can shoot longer than the 'official' 1 min limit without problem although noise increases significantly and you'll need to clean up in post. I've shot 4 min+ with my IQ160 for long exposure B&W but it does need noise clean up. The P25+ just keeps on chugging and i specifically bought it for this purpose because the resolution difference is pretty immaterial when you start shooting these types of things.
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« Reply #8 on: December 28, 2014, 01:53:05 AM »
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My research since starting this topic about two years ago shows:

The easiest solution (but not the cheapest) is to buy a Copal #0 shutter and mount a Skink Pinhole Pancake Pro Kit for Copal, Compur, Prontor #0 shutters in it. You would then mount that assembly in a lens board for a technical or view camera and adjust the distance from the lens to the sensor to suit the focal length that matches the size of the pinhole you intend to use. There are tables which show what size pinhole is the optimum for a given focal length—see below.

You then control the exposure from the flash synch socket on the shutter as usual.

A less expensive option is to glue a pinhole holder from Skink and others onto a lens board and to control the exposure using the shutter and flash sync on an external shutter or lens which you could hold in your hand. Alternatively, you could use Doug Peterson's suggestion of holding something metallic against the sync cable going to the DB. See Doug's post above.

Kapture sell a sensor activation device for Phase One backs and Leaf have a cable with a switch. see the discussion at:

 http://forum.phaseone.com/En/viewtopic.php?f=45&t=17803&p=84856&sid=d85825128a88917cd84bc0f2b9e128e9#p84856

As Doug says, you must cover the pinhole so the sensor is in complete darkness before ending the exposure by removing from the sync cable the metallic something used to fire the sensor.

You need to do this because, when the sensor is reading out data/doing black calibration, there must be complete darkness otherwise you will get strange image errors.

I originally wanted to use my Hasselblad 5xx body for pinhole work but I have abandoned that as you would have a fixed focal length of about 73mm, which is too limiting in my opinion. In theory, using a view/technical camera gives you the flexibility of different focal lengths but I have yet to test it.

For every focal length there is an optimum pinhole diameter. Lord Rayleigh's formula in Excel is =1.9*SQRT(0.00055*x)*1000 where x is the focal length and 0.00055 is the wavelength of green light in mm.

The above comments also apply to using zone plates and zone sieves with DBs.

I have ordered various components and I will edit the above to reflect reality!
Roger


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Roger Hayman
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« Reply #9 on: December 28, 2014, 02:15:03 AM »
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So, while I am waiting for my pinhole gear to arrive, I wonder if the sequence described below could be used to give multiple exposures on a DB with normal lenses.

If you have a technical camera with a sliding back and a shutter and lens as usual to control the exposure for the subject but you controlled the exposure of the DB using another shutter set to B or T and wired in the usual way to the DB, could you:

•  Compose the first shot;
•  Turn the sensor on using the shutter attached to the DB set to T or B (T is probably easiest);
•  Take the first exposure based on an ISO twice the speed of the ISO set on the back, which would end with the shutter closed;
•  Move the DB across the sliding back adapter into darkness;
•  Compose the second shot;
•  Take the second exposure based on an ISO twice the speed of the ISO set on the back, which would end with the shutter closed; and
•  Turn the sensor off using the shutter attached to the DB (press again for T or release the plunger for B).

If you wanted to combine x number of images, you would set each exposure according to an ISO which is x times the ISO set on the DB.

Would the length of time the sensor is active have any adverse effect on the image? For example, would more noise be created as the time the shutter is active increases?

Would the outcome be different from combining two images in Photoshop? Would the technique give anything of value to justify the effort?

Your feedback would be appreciated as I do not have time to test my idea right now.
Roger


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Roger Hayman
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« Reply #10 on: December 28, 2014, 05:18:18 AM »
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Although on 35mm my experiments on pinhole size do show how critical size is, depending on the result you want. My calculations showed for a Leica 35mm 0.2mm was optimal but as I was looking to mount on the Hasselblad with a P20 (regrettably not a +) as well  I ordered a 0.3mm hole as well. This shows the difference:

My concern on a technical camera where you would be varying the extension would be finding the sweet spot. Larger holes are easier to make though!!
I am mounting the 0.3mm on the 'blad soon when I fit it around other projects.
These are 10% of full frame (relative as this is an M8) from centre frame 0.2mm LHS 0.3mm RHS
A good gauge of the correct size is how well the crud on the sensor shows up!!


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