HP5 vs. Rollei Superpan 200/Aviphot 200 in tungsten light, which is fastest?

[Helge]

Looks like Aviphot 200 actually has it beat.
And not by a little.
Am I misunderstanding something?

 

[Andrew O'Neill]

HP5 is faster by a stop.

 

[Helge]

HP5 is faster by a stop.

Look at the log sensitivity. HP5 is sensitized for daylight.
Superpan 200 real speed is AFAIK 160 in daylight.

 

[Andrew O'Neill]

Look at the log sensitivity. HP5 is sensitized for daylight.
Superpan 200 real speed is AFAIK 160 in daylight.

I always thought that exposure curves determined a film's EI, not its spectral sensitivity.

 

[Helge]

I always thought that exposure curves determined a film's EI, not its spectral sensitivity.

Well both, for this type of response curve by the looks of it.
It’s obvious something is off. Most probably it’s my understanding or reading of the curve.
But it could also be that the response is radically different in tungsten.
That’s why I’m asking.

 

[pentaxuser]

Worth asking the question of Ilford? I'd have thought that it has chemists with the kind of expertise to provide a definitive answer

pentaxuser

 

[NB23]

Tungsten loses one stop. High red sensitivity film shouldn’t lose as much. So by my “educated guess”, and by not looking at the curves, I’d say both films end up being equal or a slight edge to aviphot.

 

[Don_ih]

Superpan 200 real speed is AFAIK 160 in daylight.

I expose Superpan at 160 - after several bulk rolls, I determined that was much better than 200. I like it much more than hp5, but it really doesn't like underexposure.

 

[Helge]

Had the “genius” idea of looking up SFX which is quite similar to Superpan (second is HP5 again for comparison though it’s probably the one in the comparison with the “conventional film”).
Ilford is definitely doing something different with the spectral response curve.

 

[Helge]

Found this thread:
https://www.photrio.com/forum/threads/spectral-sensitivity-of-ilford-hp5-is-for-daylight.9359/

Has anyone ever done independent measuring of Ilfords catalog of film?
Their film is second to none, but it seems very strange that they don’t dish out the detailed data they no doubt have about the film.
It would make using filters and lighting easier and more predictable.

Aviphot customers apparently won’t put up with bullshit like that.

 

[Lachlan Young]

Found this thread:
https://www.photrio.com/forum/threads/spectral-sensitivity-of-ilford-hp5-is-for-daylight.9359/

Has anyone ever done independent measuring of Ilfords catalog of film?
Their film is second to none, but it seems very strange that they don’t dish out the detailed data they no doubt have about the film.
It would make using filters and lighting easier and more predictable.

Aviphot customers apparently won’t put up with bullshit like that.

Ilford's data sheets used to be very comprehensive, but as I understand it, they reduced the amount of data published to reduce time consuming correspondence with those who couldn't or wouldn't read/ understand them. Agfa's Aviphot customers are military/ industrial & are expected to understand what they're seeing. Delta 3200 and Delta 400 seem to have re-started the somewhat more detailed info sheet. You can find the old HP5+ and FP4+ sheets etc on the web fairly easily. I've attached the equal energy plot of HP5+ from one of them.

 

[Helge]

Ilford's data sheets used to be very comprehensive, but as I understand it, they reduced the amount of data published to reduce time consuming correspondence with those who couldn't or wouldn't read/ understand them. Agfa's Aviphot customers are military/ industrial & are expected to understand what they're seeing. Delta 3200 and Delta 400 seem to have re-started the somewhat more detailed info sheet. You can find the old HP5+ and FP4+ sheets etc on the web fairly easily. I've attached the equal energy plot of HP5+ from one of them.

Thanks Lachlan!
What do I search for though? “Old data sheets for XXX film” doesn’t seem to return any desired results.

 

[Anon Ymous]

Thanks Lachlan!
What do I search for though? “Old data sheets for XXX film” doesn’t seem to return any desired results.

Check archive.org for their old datasheets. They have snapshots of the www.ilford.com website.

 

[Helge]

Check archive.org for their old datasheets. They have snapshots of the www.ilford.com website.

Nope. Blank PDFs before 2001 and the stupidified graph after that.

 

[Helge]

This also requires an understanding of what a wedge spectrograms show you. The experimental method and the plotting convention are both very important.

There are relative and absolute plots, and more importantly unless the plot indicates equal energy in some way, the graph is telling you partly about the film and partly about the spectral power distribution of the light.

Perhaps most importantly, remember that in practice this all depends on your light meter’s spectral sensitivity, and of course the spectral power distribution of natural light varies throughout the day etc. etc. (and is never equal power either).

Most general purpose black and white films are roughly daylight-balanced. Technically, the manufacturer should indicate the spectral quality of the light used to determine the ISO speed and characteristic curves. In that sense, going back to Andrew’s earlier post, the characteristic curve is related to the spectral sensitivity curve.

From a practical perspective all you might need to know is that most black and white negative films are a little slower under tungsten light than daylight. However even that is usually a moot point since you are basing your exposures on meter readings.

No, I’m basing my exposures on reflected light from zirconium bulbs without a blue filter.
So quite a tungsten like light with a lot of NIR.

 

[Anon Ymous]

Nope. Blank PDFs before 2001 and the stupidified graph after that.

I just checked a random snapshot (4/1999) and the datasheets are there:

http://web.archive.org/web/19990418005459/http://www.ilford.com/html/us_english/bw.html

In fact, I just opened the one for Delta 100.

 

[Helge]

I just checked a random snapshot (4/1999) and the datasheets are there:

http://web.archive.org/web/19990418005459/http://www.ilford.com/html/us_english/bw.html

In fact, I just opened the one for Delta 100.

They are empty apart from header and foot on my phone. I’ll check on the computer later.
Never seen that before.
Thanks.

 

[Helge]

The point is if one is using an exposure meter, the difference between the spectral sensitivity of the meter and the spectral sensitivity of the film is what is most relevant.

Yes, but that is only tangentially connected with the questions at hand.
Which film is fastest in tungsten like light?
And what is up with Ilfords data sheets?

 

[Helge]

I just checked a random snapshot (4/1999) and the datasheets are there:

http://web.archive.org/web/19990418005459/http://www.ilford.com/html/us_english/bw.html

In fact, I just opened the one for Delta 100.

Ok, doesn't work on a phone for some reason.

For completenes sake:

Ps. Amazing how little Ilfords site has really changed during the last 25 years. Stuff is just kind of bolted on to the existing core.
And their graphical identity is even older (yearly 80s I seem to be able to gather), yet still seems fresh, unique and interesting.
I could really do without the recent addition of a "Harman" band to the boxes.

 

[Lachlan Young]

Over the years both Ilford and Kodak seem to have reduced the amount of detail and also increased the weasel wording in certain cases. My guess is - at least in the Ilford case - this is marketing-driven. A simpler tech sheet is less intimidating - not to mention relatively few film users are in either the need of detailed technical information or in the position to interpret it correctly.

I'm finding it difficult to compare the two films in terms of spectral sensitivity because of the terminology and lack of detail. They both appear to be "absolute" sensitivity graphs however it is not clear to me what the light source is in the Aviphot case.

I'm pretty sure the Agfa Aviphot one is exposed to tungsten as well - the blue response is usually much higher on equal energy tests. I've attached the Agfa APX 200S data (extended red surveillance film) for comparison - Agfa tended to state that their spectral charts for still image/ ground level photographic materials were equal energy, though they don't repeat it in every data sheet.

 

[Helge]

I'm pretty sure the Agfa Aviphot one is exposed to tungsten as well - the blue response is usually much higher on equal energy tests. I've attached the Agfa APX 200S data (extended red surveillance film) for comparison - Agfa tended to state that their spectral charts for still image/ ground level photographic materials were equal energy, though they don't repeat it in every data sheet.

So according to the curves and best interpretation of them, Aviphot 200 is quite a bit faster in tungsten like light (?).

 

[Lachlan Young]

So according to the curves and best interpretation of them, Aviphot 200 is quite a bit faster in tungsten like light (?).

If you're doing aerial photography you don't want the effective speed to vary by colour of light illuminating the subject(s) - and you want the speed loss of any filters to not be disproportionate at the redder end of the scale. Whereas at sea level for normal image-making outwith IR photography etc, people seem to find materials with slightly less extreme red coverage & slightly heightened green sensitivity more preferable overall.

 

[Helge]

That sounds plausible. Though portraits of people of any colour actually often is preferred with a weighing to the red. Same with some food.

Can you cast light onto whether SFX (also a surveillance film) based on HP5, is actually slower than Superpan/Aviphot 200, or faster/same speed?
From the above, I’d say that surprisingly, it’s slower.

 

[Lachlan Young]

Can you cast light onto whether SFX (also a surveillance film) based on HP5, is actually slower than Superpan/Aviphot 200, or faster/same speed?
From the above, I’d say that surprisingly, it’s slower.

From recall, SFX is a definite ISO 200, but it's intended for ground level use at what is regarded today as ISO contrast - Aviphot Pan is EAFS 200 at higher contrasts and altitudes - if it hits an EI of 125 in Scala (BW reversal can help speeds slightly) it's probably about the same or a bit less than 125 used as a neg at sea level. It may be that SFX has a stop of acutance dye in it or similar to cut off excess IR sensitivity - or internal reflections etc.