Delta 100 in DDX 1+4 Film Test Curves

[Bill Burk]

... So, my suggestion to use f/8 at 1/500 of a second (if my metered board is f/5.6 at 1/60) would work too, right? I'm not going to use 1/60 since some of you think this may be wrong.

I think the fastest speeds are the least likely to be accurate.

You're familiar with the way the leaf shutter works right? If you use B and press slowly you may be able to watch as the blades open. First the middle opens, and then there is a star shape that expands outward until wide open, then it closes down to a star and then closed.

At the fastest speeds, when used with a wide open aperture, you get a bell-curve of exposure, which adds-up to the equivalent of your shutter speed.

I'd need someone who knows to chime in to explain what relatively fast shutter speeds have the problem of opening and closing the worst... and at which relatively slower speed it becomes a non-issue.

I don't think using 1/60 is particularly wrong, I just think your shutter is really running at 1/40. Because I know that you are a meticulous worker and every other variable is checking out. I think in your case, shutter speeds are the weakest link in the whole chain.

 

[markbarendt]

Bill,

All mechanical shutters have the same bell curve issue. It simply takes some time to get physical parts out of the way and then put them back.

Flash sync speed is the proof of this for focal plane shutters. Try to use too fast a shutter speed with flash and the shutter curtain's shadow gets in the way and shows up on the film as an underexposed band.

Leaf shutters don't have an issue with sync speed because they work like a variable aperture, as soon as they open the light from the whole scene can affect the whole film. The shutter's aperture simply gets progressively larger then progressively smaller and finally shuts. A problem with flash sync when using leaf shutters shows as a general underexposure, no band. (A flash timing lag may be caused by a slow flash triggering system "downstream" of the shutter.)

Timing problems for basic open time with either type of shutter are external, they are clockwork problems; not intrinsic problems, based on shutter type.

If the clockwork and mechanical parts are in good order there is no problem with either.

 

[StoneNYC]

So is it fair to say that a shutter exposure would be more accurate closed down than it would be wide open because of this effect/curve?

 

[K-G]

Karl, I have seen that others have also gone against Ilford's recommendation of 12 minutes for 1+4 and have developed at lower times like 7 or 8 minutes. How did you arrive at a lower development time?

So, at 12 minutes, do you think the EI I came up with, 160, is normal?

I will post my results later tonight, when I get home.

Thanks.

My personal recommendation is to not make things to complicated. If your negatives look fine when exposed after ISO 160 and developed for 12 min, then use that combination. As has been mentioned here, the fluctuations in shutterspeed accuracy and also in accuracy of aperture settings are so large , especially combined, that you just have to work out your own combination , with your own camera and your own way to develop. Spend less time on testing and more time on learning to see the light and the motifs and I think you will end up as a more happy photographer. Good luck !

Karl-Gustaf

 

[markbarendt]

So is it fair to say that a shutter exposure would be more accurate closed down than it would be wide open because of this effect/curve?

Not necessarily. It would depend on the design specification.

As a practical matter, given the 1/400 or so limit of leaf shutters, I doubt it matters.

 

[StoneNYC]

Not necessarily. It would depend on the design specification.

As a practical matter, given the 1/400 or so limit of leaf shutters, I doubt it matters.

It ALWYAS matters if you're being technical, and if you already have a lens with dark edges... I just want to know if scientifically this would be a correct statement about leaf shutters.

It has no effect on my choice of shooting, just a curious question.

 

[Bill Burk]

My thinking is that fast shutter speeds in leaf shutters have to run a little longer than the engraved time in real time so that the dim light as the shutter opens, the bright light while open fully and the dim light as the shutter closes, gives the film the sum total exposure equivalent to the engraved speed.

The smaller apertures will get opened more instantaneously, thus they get MORE exposure than equivalent setting at full aperture.

 

[StoneNYC]

My thinking is that fast shutter speeds in leaf shutters have to run a little longer than the engraved time in real time so that the dim light as the shutter opens, the bright light while open fully and the dim light as the shutter closes, gives the film the sum total exposure equivalent to the engraved speed.

The smaller apertures will get opened more instantaneously, thus they get MORE exposure than equivalent setting at full aperture.

Would this also affect sharpness? (To a microscopic degree?) because 1 the aperture isn't "round" and the light coming in is stopped down as the shutter is moving from closed to open, so that fully open shutters would have a degree of less-sharpness at the edges just by nature of the function of light in reaction to the aperture being more open at the edges of light? Or something like that? Again this wouldn't really be important for normal photography, but if a leaf shutter could run at 1/8000 would it have a greater effect and if the film were finer grained (or digital pixels with no compensation) would we have some measurable difference?

I noticed this as I recently shot something that began at f/32ish and light changed and had to go to f/8 to compensate, the image is sharp-ish but there is some strange difference in the sharpness as the aperture changed mid-exposure so did the way light hit the film during exposure.

 

[MattKing]

The f/32 portion of the exposure might involve some diffraction effects.

 

[markbarendt]

It ALWYAS matters if you're being technical, and if you already have a lens with dark edges... I just want to know if scientifically this would be a correct statement about leaf shutters.

It has no effect on my choice of shooting, just a curious question.

As a technical issue, sure it could be figured/measured.

As to the accuracy though??? You would need to ask someone who knows more.

The dark edge thing though is most likely not a shutter issue, more likely a glass issue.

 

[Xmas]

If you are doing critical work like E6 then you should compensate for shutter efficiency.

1/500 at f/16
and
1/500 at f/3.5

with your /3.5 TLR BTL shutter

have different efficiency

/16 100% - or close to
/3.5 50% - or less

say for simplicity

what you need is a Avery label stuck to the back of the hood with...

f...................8.......11........16
1/125........-..........-...........-1/3
1/250........-.......-1/3.......-2/3
1/500....-1/3....-2/3.......-1

ie at 1/500 /16 you get 5 stops less light than 1/125 /8 cause the shutter is less efficient not the 4 stops you thought... the intermediate values pro rata

I accept a bit of flaming but this is what I do...

I have no shares in Avery

 

[markbarendt]

Xmas, there are a few things we don't really know.

How fast does the shutter open and close? At 1/2 second exposure time, open and close time is probably inconsequential, at 1/400 ?

Is the open/close time always added to the exposure time that is set?

Did the manufacturer design the "count" to start when shutter reaches full open, or half open, or ... ?

Did the manufacturer do the math to figure the loss already?

Is the time adjustment infinite or does the shutter work at intermediate speeds?

Is the adjusting ring properly centered in it's detent? Does that matter?

How accurate is the adjuster for the aperture?

 

[Xmas]

Xmas, there are a few things we don't really know.

How fast does the shutter open and close? At 1/2 second exposure time, open and close time is probably inconsequential, at 1/400 ?

Is the open/close time always added to the exposure time that is set?

Did the manufacturer design the "count" to start when shutter reaches full open, or half open, or ... ?

Did the manufacturer do the math to figure the loss already?

Is the time adjustment infinite or does the shutter work at intermediate speeds?

Is the adjusting ring properly centered in it's detent? Does that matter?

How accurate is the adjuster for the aperture?

mayhap but my Avery label tells me which way the additional error is on top of all yours above, alternatively I toss a coin and get it the wrong way round, I don't claim accuracy merely the label is better than doing nothing.

And I only shoot mono.

If you use fast E6 you need to understand your points in your exposure calibration the label is generic for BTL computer style shutters.__

 

[Bill Burk]

Here is a graphic of Mario's original data points. Notice how well his points fit the ASA triangle in dashed lines.

I am backing down from my theory that Mario needs an Xmas-style Avery label, because the points don't jump around.

I still think the shutter might be 1/40 instead of 1/60.

 

[Xmas]

If you are doing critical work like E6 then you should compensate for shutter efficiency.

1/500 at f/16
and
1/500 at f/3.5

with your /3.5 TLR BTL shutter

have different efficiency

/16 100% - or close to
/3.5 50% - or less

say for simplicity

what you need is a Avery label stuck to the back of the hood with...

f...................8.......11........16
1/125........-..........-...........-1/3
1/250........-.......-1/3.......-2/3
1/500....-1/3....-2/3.......-1

ie at 1/500 /16 you get 5 stops less light than 1/125 /8 cause the shutter is less efficient not the 4 stops you thought... the intermediate values pro rata

I accept a bit of flaming but this is what I do...

I have no shares in Avery

ok I got the text wrong at 1/500 at f/16 more light is admitted the minus one stop in table is the adjustment needed from the meter to the camera to avoid overexposure with a fast film in bright light.

this is why I need the label...

the exposures are ok in a exposure value camera where you set the light value and the apertures and speeds are all linked.

overexposing mono a stop is not bad overexposing E6 is

decades since I used fast E6 in a compur style shutter.

 

[Tom Duffy]

My thinking is that fast shutter speeds in leaf shutters have to run a little longer than the engraved time in real time so that the dim light as the shutter opens, the bright light while open fully and the dim light as the shutter closes, gives the film the sum total exposure equivalent to the engraved speed.

The smaller apertures will get opened more instantaneously, thus they get MORE exposure than equivalent setting at full aperture.

Concerning leaf shutters, I had always heard there were two offsetting factors when shooting with a high shutter speed and small apertures. At high speeds the mechanical shutter runs a bit slow, e.g., maybe 1/350 or 1/400 for an indicated 1/500 shutter speed. I read in a Popular Photography article from the late '60s that this was offset at smaller apertures since a shutter is timed for the lens being wide open, e.g., 1/500 at f5.6. If I stop down to f22 the amount of time it takes the opening in the shutter to cover the smaller aperture is shorter. Yet if you watch a leaf shutter operate, it opens from the center and it would seem that at f22 the shutter would be open the longest at the center of the lens. I'm confused.

 

[markbarendt]

Yet if you watch a leaf shutter operate, it opens from the center and it would seem that at f22 the shutter would be open the longest at the center of the lens. I'm confused.

Yes, smaller apertures will always be fully open longer than larger ones. The question is "does it matter?"

The simplest way to answer the question is to do a practical test with the lenses we normally use.

Shoot say a few test frames of a test scene with constant lighting at 1/500@f4, 1/250@f5.6, 1/125@f8, 1/60@f11, 1/30@f16, 1/15@f22... or similar matched set, then measure the differences.

In this way we can know how to use our tools, though that would not answer the question globally.

 

[Oli4]

First post here!

I concur your findings. I've also done some testing over the last few weeks and I come approximately to the same conclusions. Delta 100 in 1+4 DD-x at 20C.

Initial agitation 10s, then 10 s after every min.

Delta 100 effective speed = 64
N dev time = 8m15s

Which is in fact way off then what I used to use (12m at 100 ISO).

These tests where eye-opening for me personally. I was reading all over that Delta doesn't do N+2 all that well. Now I know that's bogus. Moving forward with these numbers now.

 

[Rafal Lukawiecki]

I'm glad that this thread has been useful to a few of you. There's a related, though somewhat heated, thread at LFPP, on which I have posted a small reflection, which you might find also useful:

Since the tests, which I have published on this thread, I have verified my dev times, both in practical use and by running additional, sensitometer-exposed strips, several times, and I still stand by them.

I am a little less certain as to the EI, which I think I am slightly underrating, as this film seems faster than it claims, but I'd like to assert that with more science in the future. Still, I am pleased with the actual photographic results I am getting when printing.

At present I use 7m30s for N with EI of 100. The remaining times as per my chart in #1. Of course, I fully respect everyone's different results, due to our different technique, and different testing approaches. My results are just mine and not an indication than anyone else's are wrong.

I have also just noticed a very interesting comment in the Ilford information sheet for Delta 100: "It should be noted that the exposure index (EI) range recommended for 100 DELTA Professional is based on a practical evaluation of film speed and is not based on foot speed, as is the ISO standard.". See http://www.ilfordphoto.com/Webfiles/201062894918374.pdf

PS. See also the note that for getting maximum speed of EI 200 Ilford DDX is recommended, according to that Ilford publication. Methinks this film is faster in this combo.