Filter factor adjustment in developing

take11 · Oct 3, 2022

Hello everyone,

I hope I'm posting in the right section.

I'm going to use Ilford hp 5 plus 400 with a dark yellow filter with factor 3x (so 1.5x stop loss). I was thinking about shooting it at 800 with hand held light meter set at 400 and developing at box speed.

Shall I develop like I pushed the film or is box speed fine? Is my idea right or shall I reconsider everything?

Thanks in advance and for eventual suggestions

Anon Ymous · Oct 3, 2022

I'm not entirely sure what you mean by saying "manual meter", perhaps it's a hand held light meter? And you want to rate the film at EI800 and shoot in manual mode? Then you'll need to set 250 ISO at the light meter for a filter factor of 3 and use a development time for a 1 stop push.

AgX · Oct 3, 2022

Welcome to Apug"

The light absorbtion by a filter is compensated, if one wants to compensate for it at all, at the exposure stage, not at the developing stage.

It then is developed as normally exposed.

At the developing stage you might in addition yield a generic, not colour-wise, effect on image contrast, but this is another story.

That you contemplate about pushing indicates that you did not really understand the concept of colour filters on b&w film. Re-think or re-read on it.

take11 · Oct 3, 2022

Anon Ymous said:
I'm not entirely sure what you mean by saying "manual meter", perhaps it's a hand held light meter? And you want to rate the film at EI800 and shoot in manual mode? Then you'll need to set 250 ISO at the light meter for a filter factor of 3 and use a development time for a 1 stop push.

Ops yea I meant hand light meter. Got it thanks

koraks · Oct 3, 2022

take11 said:
Is my idea right or shall I reconsider everything?

There's no 'right' or 'wrong' in an absolute sense, but I'd say you're pretty confused about this overall.

Your film is a nominal/box speed of 400. A 1.5 stop overexposure would mean exposing as if it's ISO 140 or thereabouts.
If you insist on 'pushing' the film, so using it as if it were an 800-speed film, you would have to expose it as ca. ISO280 with your deep yellow filter.

In the first scenario you give normal development, in the second scenario you give a bit more development.

What 'normal' development is, is up to you to determine. The same for the increased development of push processing.

MattKing · Oct 3, 2022

Welcome to Photrio.
It would probably help if you defined your terms .
The "box" ISO rating for a film indicates how sensitive to light it is. If you set that speed on your meter, use the meter in a standard way, don't have a filter on the camera, set your camera and expose the film at the settings recommended by the meter, you should end up with a normally exposed film.
Then if you develop the film according to the manufacturer's recommendations, you should end up with normal negatives.
You are asking here about changes to "normal".
First, adding a filter with a filter factor of 3 will result in an under-exposed negative, unless you adjust the settings on the camera. The best way to prevent that under-exposure is to increase the exposure settings by the appropriate amount - 3x the exposure time being the most accurate.
If that change in exposure isn't possible, you can partially compensate for the under-exposure by adjusting the development. A so called "push" development doesn't really help much with the under-exposure itself. Instead, it increases the contrast. That means that although you will still lose detail in the shadows and lower, lower mid-tones (the result of under-exposure), the increase in contrast will make lower mid-tones and mid-tones look better in the results. Unfortunately, the push will often also make the highlights look worse as well, but that is part of the trade off.
Note that the under-exposure of the film is not a "push". Increasing the development and therefore the contrast is a push.
So if your goal is to make up as much as you can from the losses due to under-exposure, a "push" development corresponding with 1.5 stops will help some. I'll let those who use a lot of HP5+ pass on their advice with respect to how much extra development works best. I expect that they would like to know what type of developer is being used and, most importantly, what the subjects are and the lighting is like where you intend to photograph. Under-exposure and a push development works much, much better with even lighting and moderate contrast.

Sirius Glass · Oct 3, 2022

.

Welcome to ~~APUG~~ Photrio!!

AgX · Oct 3, 2022

MattKing said:
First, adding a filter with a filter factor of 3 will result in an under-exposed negative, unless you adjust the settings on the camera.

No, it will not.

Part of the image, those colours reduced by the filter, will be exposed lesser. The part resp. those colours not affcted by the filter, which may be the majority of the image...., will be exposed as normal.

Maybe this is just what the OP intends.

Any given correcting factor is based on the reproduction of a neutral grey to same density as without filter.
This typically is not understood !!

Also the spectral sensitivity of the film adds his share to the issue...

Based on this all one has to decide (or maybe experiment) what exposure one gives to yield the desired effect.

Pieter12 · Oct 3, 2022

The filter, regardless of color has a certain density that will affect the overall exposure of the image. Not compensating for the filter will underexpose the entire negative.

DREW WILEY · Oct 3, 2022

Altering normal development time is largely an independent question related to overall scene contrast itself, not the presence of a filter, which is instead accommodated by increasing exposure to offset the density of the filter itself. The filter factor for yellow filters with most panchromatic films is 2X. In other words, you either double your exposure time or open up one stop (not both). AgX stated it correctly.

But if you choose to expose HP5 at 800 instead of box speed of 400, what you're actually doing is lopping off a step of normal shadow value,
sacrificing it for more speed. I don't recommend doing that in any high contrast situation, though it might be OK in a low contrast situation.
In that case, you might give slightly longer than normal development time, but due to that reason alone, not because you had a filter in place.

koraks · Oct 3, 2022

Pieter12 said:
The filter, regardless of color has a certain density that will affect the overall exposure of the image.

Unless it's an exceptionally poor filter, the attenuation of an orange filter in the red and yellow parts of the spectrum will be small enough to not give big problems with underexposure. We're talking about 0.5 stop max for a poor quality filter. Of course, things get sketchier the closer you get to the filter's cutoff frequency, but that is beside the point @AgX makes.

Take for instance the rather middle-of-the road Hoya YA3. Here's the manufacturer's transmission spec:

Taken from this page: https://hoyafilter.com/product/ya3_pro_orange/

As you can see, there really is not much attenuation in the pass bandwidth of the filter. If you were to photograph a red object, no compensation would be necessary when using this filter.

Andrew O'Neill · Oct 3, 2022

take11 said:
Hello everyone,

I hope I'm posting in the right section.

I'm going to use Ilford hp 5 plus 400 with a dark yellow filter with factor 3x (so 1.5x stop loss). I was thinking about shooting it at 800 with hand held light meter set at 400 and developing at box speed.

Shall I develop like I pushed the film or is box speed fine? Is my idea right or shall I reconsider everything?

Thanks in advance and for eventual suggestions

If you intend to use it at EI 800, then push it at EI 800. If you push it at 400, then your shadows will be underexposed. If you want to push it at EI 400, then set your metre to EI 200 (or whatever to match the 3x filter factor.

AgX · Oct 3, 2022

Pieter12 said:
The filter, regardless of color has a certain density that will affect the overall exposure of the image. Not compensating for the filter will underexpose the entire negative.

Most filters have utmost high transmission (above 90%) at their colour thus no compensation for this colour will be needed.

Thus a effect of "overal exposure" or to the "entire negative" as you have it depends then on the spread of the respective colours in the image. There is no automatism as you imply.

EDIT:
I just see that Koraks already picked up this issue. Yes, green glass-filters are the typical exeption. That is why I wrote "most filters" above.

Sirius Glass · Oct 3, 2022

Pieter12 said:
The filter, regardless of color has a certain density that will affect the overall exposure of the image. Not compensating for the filter will underexpose the entire negative.

Correct!

Sirius Glass · Oct 3, 2022

koraks said:
Unless it's an exceptionally poor filter, the attenuation of an orange filter in the red and yellow parts of the spectrum will be small enough to not give big problems with underexposure. We're talking about 0.5 stop max for a poor quality filter. Of course, things get sketchier the closer you get to the filter's cutoff frequency, but that is beside the point @AgX makes.

Take for instance the rather middle-of-the road Hoya YA3. Here's the manufacturer's transmission spec:

Taken from this page: https://hoyafilter.com/product/ya3_pro_orange/

As you can see, there really is not much attenuation in the pass bandwidth of the filter. If you were to photograph a red object, no compensation would be necessary when using this filter.

Generally people do not go about looking for a poor filter.

Helge · Oct 3, 2022

Welcome to a Sirius obsession.

Sirius Glass said:
Welcome to ~~APUG~~ Photrio!!

Sirius Glass said:
Generally people do not go about looking for a poor filter.

They might end up with one regardless. Rummage sales and the usual boxes of equipment after the death of a photo nut, can contain concealed gold and concealed turds equally.

runswithsizzers · Oct 3, 2022

take11 said:
[...] I was thinking about shooting it at 800 with hand held light meter set at 400 and developing at box speed. [...]

You can EITHER "shoot it at 800" by setting your meter to ISO 800,
- OR -
You can set your meter to ISO 400, in which case you are shooting at 400.

Make sense?

Sirius Glass · Oct 3, 2022

Helge said:
Welcome to a Sirius obsession.

I like new people to feel welcome and comfortable. It might help someone overcome a reluctance to start off asking questions.

mshchem · Oct 4, 2022

I would follow the recommendation of the film and the filter manufacturers.

Steven Lee · Oct 4, 2022

take11 said:
Hello everyone,

I hope I'm posting in the right section.

I'm going to use Ilford hp 5 plus 400 with a dark yellow filter with factor 3x (so 1.5x stop loss). I was thinking about shooting it at 800 with hand held light meter set at 400 and developing at box speed.

Shall I develop like I pushed the film or is box speed fine? Is my idea right or shall I reconsider everything?

Welcome! Here's a simple answer for your simple question:

Set your handheld meter to ISO 125. If there's no setting like that, go with ISO 100. This will compensate for the filter.
Develop normally, i.e. use the development time listed for EI 400 in the film datasheet.

Enjoy!

AgX · Oct 4, 2022

mshchem said:
I would follow the recommendation of the film and the filter manufacturers.

They can only work at various situations if one understands what they mean. This understanding though is typically lacking.

Helge · Oct 4, 2022

Sirius Glass said:
I like new people to feel welcome and comfortable. It might help someone overcome a reluctance to start off asking questions.

Well that is great, and I figured as much.
But I’d hazard a guess, that some people read more into your boilerplate posts wording and graphical representation than others.

DREW WILEY · Oct 4, 2022

Koraks - do you ONLY take pictures of something either all red, or all orange, or all yellow, etc?

koraks · Oct 5, 2022

When using a red filter, I only photograph red objects. With a green filter, only green objects. Etc. I prefer to keep things nearly separated like that.

DREW WILEY · Oct 5, 2022

Ha! The bigger problem is when people look at intense colors in nature, and get fooled into thinking film and a filter will respond like their own eyes will. For instance, the fact that leaves and foliage which might look pure green to us is actually reflecting quite a bit of red, orange, or yellow light too, just as becomes apparent later in the season when the chlorophyll fades out, and the warmer hued foliage pigments become dominant.

I just do it the easy way, and apply a filter factor every single time a filter is in place. Of course, exactly what that exposure factor with any specific film might require some personal testing; but the mfg spec sheet are a good starting point and often adequate by themselves. The there's the additional fact that allegedly similar filters from different brands might vary more between one another than one might initially think.

Filter factor adjustment in developing

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