Hoya X0 filter factor/compensation

skylight1b

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I'm not sure which forum this should go in, and I feel like it's the stupidest question, but I would like to know the definitive answer on what the EV compensation and/or filter factor is for the Hoya X0 yellow-green filter.

Hoya's documentation says the necessary compensation is either 1/4 stop or 1.5 stops depending on which of their sites you reference. The chart on the back of my Hoya orange YA3 filter (X0 doesn't have one) says the X0 filter needs 1 1/3 stops compensation. In my own online research, I have seen anywhere from 1/4 to 2 stops. I actually own this filter and have used it, but I can't figure out the answer. My guess is somewhere on the lower end but not really sure.

So for those of you who own this exact filter (not another yellow-green), how many stops should one add? I know it will vary on the film being used, but 1/4 to 2 stops is a huge range.
 

DREW WILEY

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It depends on the specific film. For TMax films, my own careful testing indicates right around 1 stop. For Delta 100, it's 1-1/2 stops. For most other panchromatic films, 1-1/3 to 1-1/2 stops would be a good starting point for testing.

I have never seen a statement from Hoya or anyone else indicating only a 1/4 stop correction. That doesn't make any sense at all. And
2 stops sound more like the prescription for a deeper green X1 instead. (X1 varies from 2 to 2-1/2 stops, depending.)

But then you've got a few usual films out there with significantly different spectral sensitivity, like Fuji Acros, which is Orthopanchromatic, as well as a full Ortho film sometimes available from Ilford. These would logically respond differently.
In fact, an X0 filter in conjunction with Acros behaves almost as if it were a medium deep green X1 filter on a conventional pan film
in terms of brightening green in the scene - or should I say, over-brightening it! I won't even use an X0 with Acros. It's own native spectral signature is as if an X0 were in place when it isn't.

For critical work I advise bracketing a series of gray card exposures under representative lighting conditions and then comparing the results with densitometer readings compared to an unfiltered gray card shot without any aperture change. I use a handheld Pentax digital spotmeter for all my tests; that keeps things consistent.
 
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skylight1b

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This is really helpful! I would be curious about the effect on HP5. This is the film with which someone online swore it was only a 1/4 stop, but that seems unlikely. I think they were maybe parroting what is written on the site linked above.
 

Melvin J Bramley

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FWIW.

Filtration differences Delta 100, FP4

I've noticed a variation in how Delta 100 and FP4 filter using a yellow green filter(11). FP4 seems more normally responsive to this color than Delta 100. I'd not shot D100 with a yellow green (almost my standard on FP4. Recently, I made some pictures using D100 and an 11 - what I got on film see...
www.photo.net
 

DREW WILEY

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I don't have the exact factor for HP5. It's probably 1-1/3 stops like FP4. Most of my HP5 shooting was before I owned any X0 filters.
 

runswithsizzers

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DREW WILEY said:
[...]

I have never seen a statement from Hoya or anyone else indicating only a 1/4 stop correction. That doesn't make any sense at all. And
[...]
Click to expand...

I don't understand what they mean by it, but Hoya's web page for the X0 (Yellow Green) at --https://hoyafilter.com/product/x0_yellow_green/#specifications -- shows a specification for:
"Transmittance EV correction 1/4-stop"

 

MattKing

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I'm guessing, but that "Transmittance" reference referred to in the link from the OP and the screen shot of same referred to in runwithsizzers' post might be a reference to how much non-spectrum specific neutral density is built into the glass.
 

DREW WILEY

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Transmittance would vary a little depending on the coatings too. I personally make reference to the HMC multi-coated series - the practical net effect. I'm well aware that Hoya is an industrial contractor too, and will provides more highly detailed specs on demand. "Transmittance" refers to the glass component itself exclusive of the coloring.

For example, a no. 0 "colorless" filter from the same multicoated series has so little density that it is negligible for all practical purposes. In other words, the filter factor itself is zero.
 
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xkaes

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As an easy starting point, as Drew has alluded to, is to read a gray card (through a camera or meter) and note the exposure. Then add the filter (any filter) and see how much the meter reading has changed. No need to develop the film, but if you want to be even more exacting, add that to the mix.
 

pentaxuser

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skylight1b said:
This is really helpful! I would be curious about the effect on HP5. This is the film with which someone online swore it was only a 1/4 stop, but that seems unlikely. I think they were maybe parroting what is written on the site linked above.
Click to expand...

Yes That sounds like the song by Kirsty McColl in 1981. "There's a guy works down the chip shop swears he's Elvis but he's a liar etc.. "

I have the very same Hoya filter and in my naivety I used whatever factor that Hoya told me it was. The negs and subsequent prints all looked OK

pentaxuser
 

runswithsizzers

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I am a little fuzzy about "filter factors" -- what they mean, and how they should be used.

In the screen shot I posted in post #6, Hoya says the filter factor for their X0 Yellow-Green filter is 1.2. [notice there are no units for a factor; that is, it does not say 1.2 stops]

Looking at the Wikipedia entry for Filter Factor, I see this table:


---
Ignoring for the moment that different films have different spectral sensitivities and therefore an adjustment to the filter factor may be needed for a specific film -- according to this chart, a filter factor of 1.3 indicates the filter reduces light to 75% of the unfiltered amount, and an additional 1/3-stop of light is needed, is that right? Hoya's specification for the X0 yellow-green is a factor of 1.2 so maybe 1/4-stop additional exposure is not that far off?

However... further down on that same Wikipedia page there is another chart which shows a X0 Yellow-Green filter should have a filter factor of 2.5 -- which would suggest an additional 1-1/3rd stop of exposure. Confusing...

 
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BrianShaw

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Although this technique is fraught with error, have you metered through the filter to get a ballpark estimate of the filter factor and exposure correction?
 
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skylight1b

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BrianShaw said:
Although this technique is fraught with error, have you metered through the filter to get a ballpark estimate of the filter factor and exposure correction?
Click to expand...

I have tried to hold it carefully over an incident meter and have gotten very little if any change in exposure (as opposed to orange/YA3 which clearly was 2 stops different). When used with an in camera center-weighted meter on aperture priority, it seemed to be about 1 stop different. Neither of these techniques were great of course.
 

DREW WILEY

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I don't recommend metering through filters. You're just introducing more sketchy variables. A tested and separately applied filter factor is more reliable, especially as contrast filters start becoming deeper.

And you'll do yourself a favor by ignoring Wikipedia. For example, it cites a no.11 Wratten and Hoya X0 as equivalent. Well, they are similar; but the Wratten 11 is a little more intense. Some of the other cited examples might apply to certain brands of filters and films, but not to others. It's way too generic and dumbed-down of a list to be reliable.

Then there can be some confusion over the expressions themselves. A "filter factor" expressed as 2.5 means two and a half times the original amount of exposure, or opening up 1 and a half stops, or alternately increasing the exposure time the same amount instead. So if it's easier for one just to think in terms of aperture adjustment, that's how I expressed my own results so far on this thread.
 

runswithsizzers

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Yes, Wikipedia can be sketchy, and the manufacturer's recommendation should be more reliable. But in this case, I am finding Hoya's recommendation to be somewhat difficult to interpret because they use the expression "Transmittance EV correction" the definition of which is not immediately obvious to me.
Again, I agree -- giving a simple exposure correction in units of f-stops would help avoid confusion. But in this example, Hoya provides us with a filter factor and something called "Transmittance EV correction." I am beginning to think Hoya's Transmittance EV correction MAY be the exposure correction? That is, maybe when Hoya says, "Transmittance EV correction = 1/4-stop," they may mean increase exposure by 1/4-stop??
 
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DREW WILEY

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Just plain, No. That does not mean you increase exposure by 1/4 stop, or need to add 1/4 to the otherwise published filter factor. Hoya can probably even provide one with an actual spectrogram if they requested it from their industrial division. But again, in this particular case, when simple photographic usage is in mind, it's best not to overthink things, or try to sift through random Wicki detritus. That "transmittance EV" factor might be pertinent to an optical engineer differentiating glass types, but need not bother the rest of us. All we need to be aware of is the sum filter factor in relation to our chosen specific film, and how much correction that amounts to.
 

runswithsizzers

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In that case we are back to using an exposure factor, because Hoya does not provide us with anything more useful. So the question is, if the exposure factor is 1.2, then how many f-stops of extra exposure should be given?
 

DREW WILEY

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1.2 would indicate only a 1/5th stop correction. And that is conspicuously NOT applicable unless you're talking about a COLORLESS piece of the same filter glass. (Note that a filter factor of 1 equates to no exposure change at all - even that first Wicki chart indicates that correlation, along with the generally correct factor for an X0 in the second chart.)

So the filter factor using a light yellow-green Hoya X0 amounts to 1-1/3 to 1-1/2 stops of correction for most pan films. Hoya's own official website states, "you will need to compensate for one and a half stops of light loss when using this filter". It's that simple!

A filter factor of 1 indicates no correction needed. A factor of 2 indicates the need for double the amount of light, or one full stop of correction. A factor of 4, four times the amount of light, or two full stops. A factor of eight, three stops of correction (2 X 2 X 2 the amount of light), etc.
 
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skylight1b

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I'm grateful for all the contributions and I'm relieved to see that I'm not the only one who finds the documentation confusing. It's very straightforward for their other BW filters.
 

BrianShaw

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Looking at the specifications for the filters "on either side of X0" reveals much more correct data so I'd conclude that the specifications for X0 are typographical errors.

HOYA | Y2 Pro (Yellow)

hoyafilter.com

HOYA | X0 (Yellow Green)

hoyafilter.com

HOYA | X1 (Green)

hoyafilter.com

I'd go with this material from other Hoya documents, as a start, and forget all the rest...

 

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skylight1b

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These mirror what is said in the chart on the back of the orange filter I have. I will assume the website editor made a mistake and that Hoya didn't let the packaging go to print without it being correct.
 

BrianShaw

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skylight1b said:
These mirror what is said in the chart on the back of the orange filter I have. I will assume the website editor made a mistake and that Hoya didn't let the packaging go to print without it being correct.
Click to expand...

Hoya is a well-respected filter maker and know what they are doing. Their documentation should be correct, and usually is. I assume that the web site was developed by soemone independent of the product development/documentation area, as web sites often seem to be. Typos happen...

Where I worked there were lots of younger employees who were smitten with "automated data ingestion" to populate web sites and databases. The number of silly errors that got included would drive us engineers mad as they were very obvious... to us.
 
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runswithsizzers

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@DREW WILEY, the filter factor of 1.2 has nothing to do with Wikipedia; that number was provided by Hoya for their X0 yellow-green filter. While it seems likely that Hoya's website has a typo and their published filter factor is incorrect, consider the following:

Here are the specifications which Hoya provides online for some of their other filters:
HOYA R1 Pro (Red):
ND Number (Filter Factor) 8
Transmittance EV correction 3-stops

HOYA YA3 Pro (Orange):
ND Number (Filter Factor) 4
Transmittance EV correction 2-stops

HOYA Y2 Pro (Yellow):
ND Number (Filter Factor) 2
Transmittance EV correction 1-stop

Would you agree, that for a filter factor of 8, a 3-stop correction is indicated? And for a filter factor of 4, the correction should be 2-stops? And a filter factor of 2 indicates a 1-stop correction?

If so, then it appears Hoya is using the awkward phrase "Transmittance EV correction" to mean "exposure correction amount." And for their X0 filter, Hoya says that amount is 1/4-stop. Again, certainly not proof that the numbers are correct, especially when experience and common sense indicate othwerwise, but if I understand correctly, that is what Hoya is saying on their website.

I just sent an email inquiry to Hoya asking them to check their webpage spec for the X0 filter to see if it needs to be corrected.
 

BrianShaw

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runswithsizzers said:
...

I just sent an email inquiry to Hoya asking them to check their webpage spec for the X0 filter to see if it needs to be corrected.
Click to expand...

If you have any follow-up interaction with Hoya, would you please ask them to provide definitions for those terms, as they certainly can be figured out but may not be easily understood by laypeople. I searched their site for those terms and there seems to be no glossary. Googleing those terms helps with ND Number but Hoya appears to be alone in the use of that term for anything other than neutral density filters.
 

DREW WILEY

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runsw.... the most logical explanation in this particular instance is that a typo is indeed present.

If you want to encounter typos like crazy from a top end manufacturer, go to some of Fuji's LF lens brochures and charts. It happens.

It used to drive me crazy when the company I worked for turned the website over to entry level personnel who kept jumping the gun before we could double-check their work.

Otherwise, let me repeat one more time: Yes, a Hoya Y filter factor of 2 indicates opening up one stop of correction; a Hoya O light orange factor of 4 indicates two stops; a Hoya R (equivalent to 25 red) has a factor of 8, indicating three stops; X1 green, 2 stops. All of that corresponds to my own test results. (But not all films respond exactly the same.)

Since I shoot a lot of TMax100, my test result for the X0 yellow green filter is a filter factor of 2, equating to one stop of correctionin that case. For most other pan films, it's up to one and a half stops instead, aprox the same as the 1-1/3rd stamped on the round plastic Hoya case it came in (I haven't checked their newer rectangular packaging). I've also had dozens of printed little sheets which once came standard in the outer cardboard boxes for these filters affirming the same thing. There's nothing new going on here. It's a done deal.

For those seeking more in depth filter information shy of engineering or custom design demands, I recommend getting ahold of one of the later editions of the Kodak Wratten Filter Handbook. It's full of not only detailed specifications, but a lot of useful introductory content. Hoya filters are somewhat different, and are a far more limited selection, but numerous comparisons still apply. The closest thing to a Hoya X0 would be a Wratten 11.
 
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