exposure with filter and spotmeter

[Drew Wiley]

Even with Nikons I prefer to hand meter and apply a filter factor. I find it's far more reliable, but do realize there are a helluva lot of models of Nikon out there,
and I certainly don't have any experience with all of em.

[Pere Casals]

Even with Nikons I prefer to hand meter and apply a filter factor. I find it's far more reliable, but do realize there are a helluva lot of models of Nikon out there,
and I certainly don't have any experience with all of em.

Drew, there are only 2 Nikon models there: the F5 and the others

I collect Nikons, all are nice machines, single problem of the F5 is weight. I use it as a TTL spot photometer for the view camera, placing it in the back, so it includes bellows extension, then also I make a bracketing with same film than the sheet, after developing the roll I know how I've to develop the sheets, and what exposure was the best, useful to me to learn new films...

[alen]

How about spot metering a grey card (and white and black cards too if you wish) through the respective filter?
As long as the grey cards orientation is the same angle as the subject and in the same light, i think that would be ok.

[Greg]

The Zone VI modified meters are supposed to be accurate when you take a reading through the filters. The regular non-modified meters are not calibrated for that use.

While back I had 2 Soligor Spot Sensor meters, one stock the other Zone VI modified. Both read within a 1/4 f stop of each other. Both read within a 1/4 f stop of each other reading through the same filter, even with a Wratten 25 (red tricolor) and a Wratten 12 (deep yellow - minus blue). FYI neither agreed with my SEI which should have been the standard to match, but in the end all were so close that I got perfectly acceptable negatives using any of the 3 meters readings.

[Pere Casals]

How about spot metering a grey card (and white and black cards too if you wish) through the respective filter?
As long as the grey cards orientation is the same angle as the subject and in the same light, i think that would be ok.

It is a partial solution, I think. It can be good if subject it is not very "saturated" in color and it has a wide spectral band as the grey card has.


This do not solves the case that the spotmeter has not a flat spectral sensitivity curve and that a color filter will darken some colors more than others. For example if we have an sky that will be everexposed and we want to know the effect of the filter, to know if the sky will drop 2 zones or 1 zone relative to the earth with a yellow filter. Some scenes have a high dynamic range that it is difficult to capture.

if we look the spectral sensitivity chart of the Pentax 5 (http://www.pacificrimcamera.com/rl/00042/00042.pdf) we see that sensitivity for blue is 50% of what it can be expected. So sky will be more overexposed than hat Pentax V says by pointing up, and this effect will be increased with a yellow filter on.


So it is not easy, and we can go to the problem by two ways. One is with real field experience, knowing is a Zone 7 sky is nice. The other way is by using charts to figure what will happen.

I think best option is combining both ways: knowing the theory of what happens, and looking what happens in practice.

Anyway I think that Doremus Scudder is right in what he says in post #9.

A Spotmeter it is very usefull know what contrast we'll have in a photograph, and it is also useful to know how contrast will change with placing the filter on the spotmeter, but corrections are needed.

[McAir]

I am just returning to LF black and white after a number of years. I used to meter through filters with my Pentax spot. Now as I refresh some of my techniques and reading this thread, my head is about to explode. Now, I'm not sure yet how I will be going forward. Seems like it might be ballpark except Red #25, which maybe should use recommended factor for the filter as a starting point. Maybe end up doing some testing but I sure didn't realize this was such a complicated issue.

[Drew Wiley]

Welcome back. The older threads mainly addressed the fact that meters do not have equal sensitivity across the whole spectrum. So if you take a reading through a filter it might not be correct. But another reason to apply a filter factor instead or reading through a filter is fact no. 2 : different kinds of panchromatic film themselves also differ somewhat in spectral sensitivity. For example, by careful testing with gray card exposures and densitometer readings afterwards, I discovered there was half a stop of difference in filter factor between Delta 100 and TMax 100 using a med green Hoya X1 filter.

Some people might shrug their shoulders about what seems to them a small difference. But those are apt to be the same people who shrug off several other factors under pretense of exposure latitude; and all those seemingly little things soon add us to a serious exposure error.

[John Layton]

...about those grey cards - be very careful of the cheap, shiny cardboard ones - as they can exhibit just a tad too much specularity, (depending on light quality) which can really throw readings off. About the only grey card that I've ever really trusted is called "The Last Grey Card," which is made from a tough plastic and which has a very slight, almost velvety texture.

[Alan Klein]

Curious how readings work with a polarizing filter since the stops change depending on how much you rotate it?

[BrianShaw]

Curious how readings work with a polarizing filter since the stops change depending on how much you rotate it?

It's an easy experiment, Alan. There might be difference between linear and circular polarizer, so 2 easy experiments perhaps.