Various Recirocity Failure charts.

[AdQuo]

Hi.
I´ve been looking for reciprocity failure compensation and I´ve found several different tables.
in the next document you can find the two most "reliables" for all comments post with them. One ¡s by Howard Bond and the other one was submited by Les McLean.

I´m trying to find out times for Kodak triX400, TMax100, FP4+ and HP5+

http://www.megaupload.com/?d=FH5URNQ9

I you compare them you can see that for any film, adjusting times may difer very much from one to another table. It can even be multipled by 4!!!
I cannot believe that such different times can be both right.

So, does anyone make long exposure photography? If so, which times do you use?

Thanks for your help!

Sincerely

Ivan

 

[tlitody]

If the film is old type and not T-Grain type then the Ilford charts you can get at their website will work fine. They may work with T-Grain too but I haven't tried.
However, forget about expose for the shadows and dev for the highlights. Meter a highlight using a spot meter and if and only if the highlight falls into reciprocity, then adjust using Ilfords recommendation from the chart. When I say highlight I mean something that is around zone 7 or 8 if you were using the zone system.
Unbelievable as it may sound, the shadows will take care of themselves.
Now what I have just suggested will work absolutely fine providing you don't over develop and infact a one stop pull will make it almost full proof unless even the highlights are very dim. But in that case you would be photographing in almost total blackness and all bets are off.

 

[AdQuo]

Ok Great!
All pictures I made I never metered in spot mode; just reflected and generally on the scene. I will try to meter that zone 7 or 8.
When you find exposure times of 15 secons, you adjust with the chart that Ilford provides, don´t you? What makes me puzzled is in the charts I included, for example, for metered time of 15 seconds, Howard Bond increased time up to 24 seconds while the table by Les, goes up to 45! Almost double! This is what I cannot understand; with such different times are both to be correct?

Ilford is a newer film, surely made with latest technology but what about when you use TriX or TMax?

Please excuse me for all my doubts!

 

[tlitody]

Ok Great!
All pictures I made I never metered in spot mode; just reflected and generally on the scene. I will try to meter that zone 7 or 8.
When you find exposure times of 15 secons, you adjust with the chart that Ilford provides, don´t you? What makes me puzzled is in the charts I included, for example, for metered time of 15 seconds, Howard Bond increased time up to 24 seconds while the table by Les, goes up to 45! Almost double! This is what I cannot understand; with such different times are both to be correct?

Ilford is a newer film, surely made with latest technology but what about when you use TriX or TMax?

Please excuse me for all my doubts!

TriX is old type film. TMax is newer T-grain.
Ilford HP5 and FP4 or old type films, Delta is newer T-Grain.
Fuji Acros which is also a hybrid T-Grain film allows 2 minute exposures before it goes into reciprocity. But its only 100 speed and if you pull it one stop to 50 then its 3 stops slower than a 400 speed film used at box speed so the gain isn't that much. I really like HP5 for night time shots.

The problem with all these reciprocity methods that people give is that they never tell you what they have calibrated their normal development to or if they are using manufacturers recommended development when exposed at box speed. And they never tell you exactly how they are metering which can make a big difference. So I take them all with a pinch of salt.

The biggest question is what sort of subject you are photographing and how dark it is. In a typical scene which usually has some lighting in it, then its those highlights which need to exposed properly to get a good rendition. Hell its dark so you expect the shadows to be dark and blocked. But if you meter the shadows and try and put them up with reciprocity correction, you will blow your highlights out unless you give massive development pulling. So just let the shadows go where they go cos it's the mid to highlights that are most important at night IMO. If your metering says a zone 8 needs 4 seconds then just read off the ilford chart what time that should be exposed at and you will more or less nail it first time.
If you pull one stop from box speed you are effectively reducing contrast which can be high with night time shots. So that is why I suggest doing it as helps the image not to look like chalk and charcoal. So with a 400 speed film, expose at 200 and reduce manufacturer recommended development for box speed by around 25%. Then just meter your zone 7 or 8. And don't be tempted to meter specular highlights cos that will throw you off.

 

[AdQuo]

Yes. Im agree with you; people just give adjusting times but dont say for which conditions or haw they mettered!
I will give up using TMAX for long exposure and start with FP4+ and aply the adjusting times by Ilford (Ec=Em^1.48). I will just make a table using this formula and apply.

Thank you so much for this surprising advice; "expose for highlights"; I would have never done it properly!

Again, THANK YOU VERY MUCH!

 

[tlitody]

Yes. Im agree with you; people just give adjusting times but dont say for which conditions or haw they mettered!
I will give up using TMAX for long exposure and start with FP4+ and aply the adjusting times by Ilford (Ec=Em^1.48). I will just make a table using this formula and apply.

Thank you so much for this surprising advice; "expose for highlights"; I would have never done it properly!

Again, THANK YOU VERY MUCH!

There's always more than one way to skin a cat 😀

One other thing. If you are exposing at box speed using manufacturers recommended development times and not pulling 1 stop. Then treat each zone as 0.8 stops and not 1 stop. So for zone 7 instead of opening up 2 stops from metered only open up 1.5 stops and for zone 8 only open up 2.5 stops.
This because zone system is based on 10 stop range whereas manufacturers range is only around 8 stops for same highlight(white) neg density.

 

[tlitody]

As an aside its worth knowing that your eyes play tricks on you at night. Firstly they use different cones in the dark which don't correspond to daylight vision. So what you can see in the shadows is different than what you think the film will see. This results in you making false assumptions about what is a zone 3 for example. The tendancy is to try and make shadows too light if you meter for them at night time. The result is again too much exposure for the highlights. Its much easier to assess highlights visually at night than it is to assess shadows IMO.

 

[tlitody]

One other thing. If you meter a zone 3 and work out the reciprocity adjustment and then meter a highlight and work out the reciprocity adjustment , you will often find you get different final exposures. This is because dark areas of the subject may well be further into reciprocity than the light areas. Again another reason to meter the mid to high values which are crucial to a good result. Infact it is possible that brighly illuminated areas at night(by flood lights for example) don't require any reciprocity adjustment whereas the deep shadows indicate you do need it. So you have to ask yourself which is the correct portion of the subject to take the reading from? If you pick the shadows and adjust for reciprocity you will blow the highlights and if you meter the mid to high values then they will be correct and the shadows will be very deep or black. Well thats fine because its night time and that is what you would expect at night.

 

[Roger Hicks]

Generlly, the manufacturers' figures are the most reliable, and based on ISO exposure criteria (density and contrast). To quote an Ilford spokesman, "Why would we lie? Spite? Or because we don't want you to get the best possible results out of our film?"

Cheers,

R.

 

[tlitody]

An example using the metering technique I describe. The actual print looks better, it shows plenty detail in those shadows. Long time ago but I beleive I metered the clock tower. Had I metered the close shadows and worked out reciprocity for those, the clock tower would have been blown out or at a minimum very difficult to print down. As it is its a straight print with no burning or dodging to do.

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