Hasselblad 500c and Phase One P45 Back - long exposure not working?

[kristyansen]

What position should the lenses be in?
a) for „normal“ exposures and
b) for „B“ exposure?

The lenses that work well are in X mode. No issue.

 

[FloatingLens]

Ah sorry, I meant M mode on the compur shutter because that one will NOT have the required sync timing.

 

[itsdoable]

The P45 is ready when it gets the wakeup call, and starts integrating light when it gets the sync signal, which is when the contacts close, and stops when the contacts open. If the contacts in the lens do not stay closed, or are noisy, the back may assume the exposure is over.

Note that the flash contacts are tricky to aligne when reassembling a C lens.

The back should work in both X and M mode. M will pretrigger the back, same as using the body sync. X will allow the back to cycle faster, and record the estimated shutter speed on the exif metadata, it's usually pretty close. M will record a much longer shutter speed.

 

[kristyansen]

A wake-up cable allows Phase One digital backs to be used on cameras with mechanical shutters. It has a button that, when pushed, wakes up the digital back.
Here is a graphic from my site of the type I use (there are less expensive cables available):

--

It sounds like a timing (latency) issue.
You may need to use a wake-up cable in long latency mode.
I know what the manual says about short latency, but that is not working!

Try this, as this is how I do long exposures with my tech cameras and the P45:

1. Attach wake-up cable to the P45 back
2. PC flash sync to the lens
3. Put the camera in B mode
4. Press the wake-up cable,
5. Then do your long exposure in B mode with the mirror locked up

Let us know how it goes.
Best of luck!

While thinking of options regarding some of my lenses being CLAed, I am still intrigued about this special wake-up cable.
@darr if you have some seconds I would be grateful for some more details on Step 5:

• When does the exposure on the body actually start and end, and how?
• When should the mirror locked-up - after waking up the body or before?
• Do I lock the mirror up from the special 500C button below the winding knob or by pressing the shutter button of the camera and holding it pressed and eventually depressing it?
• When is the shutter knob of the body being pressed, when is it depressed? (thus activating the lens PC sync...) - if at all?
• Do I need to press the wake-up knob of the cable again at the end of the photo?

Apologies for the many questions but I am really interested in this technique which seems less dependent on some not so reliable lens contacts...

 

[darr]

The only thing 'special' about the ALPA cable is it is made to attach to ALPA camera bodies (with the proper attachment).

The steps I went through are the ones I go through when performing a long exposure on my Hasselblad bodies.
Nothing special there, either. You said you were doing long exposures with a Hasselblad 500.

My P45 is an M645, not a Hasselblad V. My V digital backs have Live View, which is much easier to use with my Hasselblad bodies.

 

[darr]

• When does the exposure on the body actually start and end, and how?
• When should the mirror locked-up - after waking up the body or before?
• Do I lock the mirror up from the special 500C button below the winding knob or by pressing the shutter button of the camera and holding it pressed and eventually depressing it?
• When is the shutter knob of the body being pressed, when is it depressed? (thus activating the lens PC sync...) - if at all?
• Do I need to press the wake-up knob of the cable again at the end of the photo?

1) exposure happens when you open the lens after mirror lock-up
2) prepare your camera body before wake-up
3) mirror lock-up first with the lever below the winding knob
4) after mirror lock-up, press wake-up cable, then quickly press the shutter release cable
5) There is no need to wake-up the back again after the exposure

 

[darr]

You are operating a film camera first, then a digital back.

It can be overwhelming if you are not an experienced Hasselblad film shooter, as shooting older medium-format film cameras has distinct shooting checklists and is nothing like shooting a digital camera. Practice, practice, practice, as I said when I taught.

 

[kristyansen]

Thank you, Darr, yes, I am getting better at it.

Regarding the wake-up cable, I understand that the lens must still send the signal correctly to the digital back to end the exposure, so if my lens does send the signal too early while the exposure is still ongoing (the release button is still pressed), the wake-up cable will not solve the issue I am having and cannot send the end exposure signal to the digital back.

Thanks again!

 

[darr]

The P45 back functions within a sleeping architecture. It requires two signals: one to awaken and another to initiate exposure. This design ensures the CCD remains as cool as possible, eliminating the need for external cooling.

I have used wake-up cables with a push button to wake up the back and a shutter release cable to take the picture after the back awakes.
If you see a timeout error, the back gets your first signal and never gets the second one.

I do not think the statement "the lens must still send the signal correctly to the digital back to end the exposure" is correct. The second signal opens the lens shutter, and then the shutter closes as it would normally, and the back no longer receives any light, thus ending the exposure. I would like someone to clarify this.

So, are you saying your lens shutter is not operating correctly?
Did you try another lens and have success?

The Hasselblad 'C' lenses are old, some from the 1950s. I used them at the start of my career in the 1980s, and at least one 'C' lens was in the shop monthly, having the flash sync replaced. Sometimes, they even had burn marks on the metal from all the pop flashes I fired from them at special events, weddings, etc. The flash sync stub sticking out of the lenses caused problems with new assistants pulling the cords off haphazardly.

I never want to discourage a photographer from using Hasselblad gear, but old Hasselblad gear with digital backs might be challenging unless you have a good repair person.

Then, there is a possible shutter-in-body issue. Did you have a technician look at the body as well?

 

[anwarp]

do not think the statement "the lens must still send the signal correctly to the digital back to end the exposure" is correct. The second signal opens the lens shutter, and then the shutter closes as it would normally, and the back no longer receives any light, thus ending the exposure. I would like someone to clarify this.

Actually the back does need a signal from the shutter to stop.
The wake up signal is a brief pulse to tell the controller to wake up the sensor. When the shutter opens a switch closes and should remain closed until the shutter closes again.
At this point, the controller can start reading the data from the sensor.

If the switch contacts are dirty or oxidised, the signal from the shutter may stop intermittently, causing the controller in the back to mistake it for the end of the exposure.
it will then start the dark reference exposure (while the shutter is still open) and really mess the image up.

 

[darr]

Actually the back does need a signal from the shutter to stop.
The wake up signal is a brief pulse to tell the controller to wake up the sensor. When the shutter opens a switch closes and should remain closed until the shutter closes again.
At this point, the controller can start reading the data from the sensor.

If the switch contacts are dirty or oxidised, the signal from the shutter may stop intermittently, causing the controller in the back to mistake it for the end of the exposure.
it will then start the dark reference exposure (while the shutter is still open) and really mess the image up.

Thank you. I did not know what happens in the back after the shutter closes.

 

[anwarp]

Actually, my last sentence is incorrect.
The exposure will finish early if the shutter-is-open signal is interrupted, but the reference darkframe will only happen once the user confirms that the shutter has been closed.

 

[kristyansen]

Hi @darr and @anwarp, thank you.
Yes my Planar C 80 and an independent Planar C 80 from an owner of a photo store dealing with many older Hasselblads have the same effect on the digital back on B - the exposure cuts in the middle after a few seconds. This gets me the question - were all Planar lenses like that? Normal speeds without B are ok, but B is important to me.
Other C lenses such as a 50 or 150 work. Very interesting.

 

[darr]

Sorry, I do not know about the ‘C’ 80 lens and the ‘B’setting problem. We had a very knowledgeable Hasselblad repair guy for decades, but he sadly passed away last year; David Odess, RIP. Let me see if two of this forum’s Hasselblad experts can chime in. @docholliday @TechTalk

In the meantime, I will do some research about this and report back.

Darr

 

[kristyansen]

Thank you so much - it could be hard to find something - for film this would no issue since flash sync would work as the PC-Sync sends one signal. Maybe the solution is indeed to switch to a newer Planar 80 type, I have not yet tested one though…

 

[mristuccia]

So, firstly I must admit that I've not read the whole discussion here.

I can confirm however that my Planar C 80 behaves the same way as you've described: on B, the PC-sync circuit opens a second after it closes, and that happens even if the camera (shutter) trigger is still pressed. That shows a different behaviour from, for example, my CF 60. The CF 60 keeps the PC-sync circuit closed till the camera trigger is released and the shutter closes.
This is not a show-stopper for me, as on my digital back (CFV-50c) I can set the minimum exposure duration. Once triggered by the PC-sync, my back exposes in any case for the configured amount of seconds and then, if the PC-sync circuit is still closed, it continues until it opens.

So, on B, with the C 80 my back exposes only for the configured exposure duration, while with the CF 60 it exposes at least for the configured duration and then, when this moment is reached, it continues till I release the camera trigger.

Unfortunately I don't have a CF/CFi 80 to compare the behaviour.

 

[anwarp]

Here is an experiment you can try.

1. do not connect the cable to the sync socket on the lens
2. wake the back like you usually do
3. with a paprclip or something similar, short the centre pin in the cable with the outer shell. This should start the exposure on the back, but as the shutter is still closed, it doesn’t matter.
4. trip the shutter to make the exposure
5. After the desired period, close the shutter, then remove the short from the cable to finish the exposure.

If this works, the problem is with the shutter.

 

[itsdoable]

Hi @darr and @anwarp, thank you.
Yes my Planar C 80 and an independent Planar C 80 from an owner of a photo store dealing with many older Hasselblads have the same effect on the digital back on B - the exposure cuts in the middle after a few seconds. This gets me the question - were all Planar lenses like that? Normal speeds without B are ok, but B is important to me.
Other C lenses such as a 50 or 150 work. Very interesting.

This and mristuccia's observations are interesting, as the 4/50, 3.5/60, 2.8/80, 5.6/120, 4/150 and 5.6/250 all use the same Compur shutter, in that you can interchange them between lenses. So the flash contact behaviour should be the same.

One thing to keep in mind is these older C lenses were used with +300V flash syncs, so the sync contact in the shutters typically shows arcing damage. These are inside the shutter, so the contacts are not easily replaceable, but for electronic flash, this is not usually a problem. Mechanically, the contacts close when the shutter opens, and open when the shutter closes. For electronic flash the 1st closing contact is all it needs, so damage/service/modifications to the shutter that did not maintain the sync contact while the shutter is open would not affect this function.

 

[docholliday]

If that's an old 500C body, does it have the sync port in the side of the body? If it does, that syncs with the rear baffles instead of the lens and might do the trick. Since it stays closed as long as the baffles are open, it should give the back the sync it needs. It doesn't matter if you are in long B exposures since there's no need to sync to the lens opening - the sensor is just on whilest recording blackness if the lens shutter isn't opened yet.

I never owned any of the chromey C lenses. I've always had at least CF, but mostly CFi, CFe, and F lenses. I've also never owned any 500/501 bodies. I've always had at least 503 bodies and a lot of 20x bodies. The 500c, some 500c/m, and I'm not sure on the 500cm had the body shutters (they were technically used for M sync, not the lenses X sync).

One thing about all of the C lenses (new and old) is that the sync contact are mechanical, and hence prone to oxidation/corrosion. They may close, but can get a high resistance. That is fine to "pulse" a strobe which is only looking for 100ms contact, but extended duration may result in loss of "sync" because the resistance is going up as the spring pressure equals out over a few seconds. The contact can usually be cleaned with something like some 10000-15000 grit material, like what we use to smooth out fountain pen nibs. It's like filing points on old cars to clean up the carbon buildup. I also tend to put a tiny drop of DeOxit red on the contacts to keep them from oxidizing further.

If you can get an ohmmeter and old sync cable, you can put it in resistance mode, cut the old cable and connect the meter across the wires (no polarity, just one lead on the center and the other on the shield), fire the lens and watch to see what it does. It should go down to < 1Ω and stay there. If it goes back open immediately, the contact are opening back up. If the resistance starts to vary, jump, or climb, it's most likely corrosion.

 

[kristyansen]

Here is an experiment you can try.

1. do not connect the cable to the sync socket on the lens
2. wake the back like you usually do
3. with a paprclip or something similar, short the centre pin in the cable with the outer shell. This should start the exposure on the back, but as the shutter is still closed, it doesn’t matter.
4. trip the shutter to make the exposure
5. After the desired period, close the shutter, then remove the short from the cable to finish the exposure.

If this works, the problem is with the shutter.

Hi @anwarp thanks for the idea, I will investigate this, I hope later in the week. I am quite curious myself how it behaves. I will report back.