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  #21  
Old 23rd August 2013, 08:53 PM
Michael Michael is offline
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This interesting thread provoked me into wanting a copy; so I ordered it direct from Mr Barnbaum (not Baunbaum, by the way). It arrived today, signed by him for a small extra charge; and I'm looking forward to read it. Will never catch up with some of you lot though!
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  #22  
Old 28th August 2013, 10:00 AM
Mark Snowdon Mark Snowdon is offline
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Just to fan the flames of the zone III vs zone IV debate, here is a link to a YouTube clip of Bruce Barnbaum talking about why he places shadows on zone IV and not III:-

www.youtube.com/watch?v=rlnt5yFArWo

Since reading his book I have started to follow his advice regarding the placement of the shadows, with reduced development to control the highlights if needed and I must say that the negs look all the better for it. Contrast in the shadows is excellent as you would expect.

Another interesting tip he gives is the use of long exposures, using a ND filter if necessary, to give N+1 to negs. So if you have a roll of film and you do not want to give extended development to the whole film as only a few frames would benefit from it, you can use the expansion properties of long exposures to give N+1 to just those frames, whilst giving normal development to the film as a whole.
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  #23  
Old 28th August 2013, 05:07 PM
peterlg peterlg is offline
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Quote:
Originally Posted by Mark Snowdon View Post

Another interesting tip he gives is the use of long exposures, using a ND filter if necessary, to give N+1 to negs. So if you have a roll of film and you do not want to give extended development to the whole film as only a few frames would benefit from it, you can use the expansion properties of long exposures to give N+1 to just those frames, whilst giving normal development to the film as a whole.
hello Mark,
just listened to Barnbaum on the Youtube clip. Fine explanation of difference between tonality and texture - I'll certainly try if I can improve my negs - I know the problem with flat prints!
You make another point about long exposures. I don't quite understand what's the use of this with relation to development? If you measure the shadows and put them on zone IV, what's the difference between using f22-1/500 and say f2-1/8 sec?
Peter
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  #24  
Old 28th August 2013, 05:09 PM
Mike O'Pray Mike O'Pray is offline
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Quote:
Originally Posted by Mark Snowdon View Post

Another interesting tip he gives is the use of long exposures, using a ND filter if necessary, to give N+1 to negs. So if you have a roll of film and you do not want to give extended development to the whole film as only a few frames would benefit from it, you can use the expansion properties of long exposures to give N+1 to just those frames, whilst giving normal development to the film as a whole.
I am a little lost here. I had always thought that ND filters simply allowed increased shutter speeds to prevent existing top end camera shutter speeds from being too short thus giving overexposure. An example being a D3200 film in the camera with an unexpected bright day and the need for say 1/2000th when the top speed on the camera is 1/1000th and changing aperture to compensate for correct exposure isn't acceptable when you want shallow DoF

Can a ND filter change things simply by increasing exposure when by allowing the same bigger aperture to remain appropriate? What I am somewhat longwindedly getting to is that my assumption is that the ND doesn't change the correct EV setting for the shot but simply allows for a bigger aperture.

The best example of this and one that makes sense to me which I have seen is a shot of a motorway requiring a certain EV for proper exposure but with the requirement to show it as if there were no vehicles there by slowing the shutter speed so that fast moving vehicles aren't recorded.

Am I missing a use of ND which actually does something that simply manually increasing the exposure for shadow density to ZIV instead of ZIII in that frame doesn't

Thanks

Mike
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  #25  
Old 28th August 2013, 07:03 PM
Mark Snowdon Mark Snowdon is offline
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The ND filter does not increase contrast itself it is the long exposure which it allows that will give expansion to the neg. Reciprocity characteristics come in useful in this case. If you give a film an exposure of say 60secs this will give n+1 with the neg developed normally. Long exposures give increased contrast.

That is why film manufacturers recommend a cut in development time for long exposures to compensate for the increase in contrast.

Hope this makes sense?

Mark
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  #26  
Old 28th August 2013, 07:18 PM
Mike O'Pray Mike O'Pray is offline
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Thanks, I hadn't realised this. So the exposure at the same EV as is achieved with a shorter exposure time but bigger aperture to achieve the correct light quantity hitting the neg will deny you increased contrast compared with longer exposure but the same EV which takes into account the correct light quantity?

Any idea how this works in simple theoretical film terms?

Mike
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  #27  
Old 28th August 2013, 08:25 PM
Mark Snowdon Mark Snowdon is offline
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Hi Mike / Peter,

The sensitivity loss of film depends on the amount of light falling onto it. In low light the shadows are more affected by this reciprocity failure than the highlights which receive more light. This means that reciprocity failure tends to increase contrast because exposure is reduced more in the shadows than the highlights. So if you expose enough to get good shadow detail you will raise the value of the highlights. This is why you need reduced development to bring the highlights down.

So if you have a low contrast scene with the shadows on Z4 and highlights on Z6 say and you want the highlights on Z7 instead you can either give more development or use reciprocity failure to give you this expansion by giving a long exposure of say 60secs.
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  #28  
Old 28th August 2013, 09:41 PM
Mike O'Pray Mike O'Pray is offline
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So to gain the benefit of this reciprocity failure you presumably need to increase the exposure to that level at which reciprocity failure takes effect. Do you then apply the compensatory increase in exposure that reciprocity problem gives or simply ignore this aspect and rely on what the camera's meter says?

In other words any increase in exposure time that gets you into the reciprocity failure area will work?

I have to say I don't recall seeing this as a method in any book but it may be that it was explained but didn't register with me. Things often fail to register with me until I have read a book several times

The reciprocity gap increases with the increased exposure method via a ND filter so is there a way of working out where the exposure has to be to give the right level for say a one zone increase as you mention in your last paragraph?

While reciprocity failure will occur after as little as 1-2 secs with some film, you presumably should avoid the likes of Acros where it doesn't occur until after 120 secs unless you want a long wait

The other problem I see with this method occurs with any shot that requires motion to be stopped so it has to be used with static scenes only.

Mike
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  #29  
Old 29th August 2013, 07:39 AM
Mark Snowdon Mark Snowdon is offline
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Hi Mike,

You need to use an exposure time where reciprocity failure occurs if you want to get expansion, (eg N+1). Also you have to apply the increased exposure indicated on reciprocity charts / graphs otherwise your neg will be underexposed. Any exposure which puts you into reciprocity failure will give a degree of expansion.

I first saw info on this many years ago in some Agfa tech literature for the old Agfapan films (pre APX), and it is of course in Bruce B's book. In the Agfa literature it advised reducing development when using long exposures with its films to compensate for the increase in contrast.

There is a table in Bruce B's book for Tri-X, I think, but it will be different depending on what film you are using and what reciprocity characteristics it has. As you say, expansion with long exposures on Acros probably would not happen because of its good reciprocity characteristics.

Also I expect this is something that has to be taken into account with pinhole work as you normally end up with long exposures due to the use of a very small f number.

It is only since reading Bruce B's book that I have started thinking about this. It probably explains why many of my pinhole photos have not worked. In future I will give reduced dev to my pinhole films to compensate for the increase in contrast, unless of course I am photographing a low contrast subject.

Mark
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  #30  
Old 29th August 2013, 12:41 PM
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dsallen dsallen is offline
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Quote:
Originally Posted by Les McLean View Post
David, this does make an interesting subject for discussion re methods of determining exposure.


I used a Weston IV when I first made photographs but the friend who guided me to the Zone System also suggested I would be well advised to use a spot meter so I did as I was told and purchased my Soligor Analogue meter for £59, what a bargain and my friend was right. I still use the same meter. My Zone tests were done using the spot meter.


You are right on the mark regarding the problem of flare when using a spot meter, luckily I spotted the problem quite early and solved it simply by shielding the lens with my left hand by cupping it around the top of the lens as I made my reading. I still use that method today, perhaps I'll nick your toilet toll core dodge but ensure that you get the credit Flare on the spot meter lens could result in underexposure by as much as two stops.


Please bare with me while I explain another reason why I think placing shadows on Zone IV produces a better negative, particularly in the shadows.


Imagine we are making a photograph of a passage with a closed, black gloss painted panelled door at the end of this longish dark passage also with dark painted walls. The passage is lit by natural light from one small window on one side wall. The black door does reflect a little of the window light which does not directly light the door. I metered the darkest part of the door and placed it on Zone IV. I could not meter the darkest area in the picture even with a spot meter because it was too small, but for me it was essential that I show difference in tone between the door and the small area of darkness between it and the frame. I also metered the lightest area I wanted in the final print simply to determine the contrast range which governed how I would develop the film.


The resulting negative enabled me to make a print that showed the subtle differences in tone on the black painted, dimly lit door and quite clearly showed the black rim of darkness between the door and the frame. I had total separation in the shadows and an image on the paper that had quite considerable depth because of that separation. Placing the readable shadow on Zone III would have resulted in no separation at all and a negative that would have been very difficult to print. I always read my shadows in that manner and place them on Zone IV for there are dark little corners in shadows that are so easily lost at the metering stage.
Hi Les,

having mulled over your example, I have to say that I would be confident in getting a good result placing my shadows on Zone III. I think the difference between our approaches must be down to where the film is calibrated (of course, in practice, so long as we both achieve the results that we want it doesn't matter if you use Zone IV and I use Zone III).

In the video of Bruce Barnbaum explaining why he uses Zone IV, there is a clear demonstration of how he has misinterpreted the fundamentals of the Zone System. He quite correctly refers to the toe of the curve being flat and therefore leading to a lack of separation (or texture in his parlance). However, the point of 'real world' testing to establish your personal Exposure Index is to ensure that no part of Zone III lies on the toe. In effect, he is saying that he places Zone III to low down on the curve (thereby landing on the toe) and therefore has to place his shadows on Zone IV.

All of this can be quite ambiguous when using Zone system terms as
the placing of a particular area of a scene on a particular Zone tells other photographers nothing if they do not know where you have set your Zones I, II and III in reference to the toe. Perhaps it would be more helpful to give an example with exposure used as people can then refer to what exposure they would have given using their own methods of exposure and development.

Generally, in Berlin, because of the buildings being 5 stories high (about the equivalent to 8 stories in a typical post war block in the UK) there are often areas in deep shadow and, as many buildings are plastered in white (or near white colour) there is a high subject brightness ratio. Often this results in the shadow area I want to render dark but with detail falling on 10 on the Weston exposure dial (highlights often land on 16 or even higher). This equates to an exposure of 1/60 @ f16 when using Delta 400 rated at a personal exposure index of 200 in a Mamiya 7 with 65mm lens and developed in Barry Thornton's two-bath developer. As you can see, this is a long way from 'Sunny 16) but is an exposure that delivers consistently good shadow detail.

A quick comment on the N+1 expansion with reciprocity - I just don't get it. The expansion can only happen if you use the reciprocity failure to loose shadow detail. If you give adequate exposure to the shadows and control you development accordingly, you will have a correctly exposed negative. My main experience of long exposures is with night time photography in the city. Here, the subject brightness range can be huge. However, as I use a two-bath developer and know that my highlights will not be blown, I still use the same approach to metering: meter the shadow area I want to retain detail and place it on Zone III. This approach works consistently well even if there are streetlights captured within the image.

Bests,

David
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