Look at the log sensitivity. HP5 is sensitized for daylight.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.
Well both, for this type of response curve by the looks of it.I always thought that exposure curves determined a film's EI, not its spectral sensitivity.
Superpan 200 real speed is AFAIK 160 in daylight.
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.
Thanks Lachlan!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.
Check archive.org for their old datasheets. They have snapshots of the www.ilford.com website.Thanks Lachlan!
What do I search for though? “Old data sheets for XXX film” doesn’t seem to return any desired results.
Nope. Blank PDFs before 2001 and the stupidified graph after that.Check archive.org for their old datasheets. They have snapshots of the www.ilford.com website.
No, I’m basing my exposures on reflected light from zirconium bulbs without a blue filter.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.
I just checked a random snapshot (4/1999) and the datasheets are there:Nope. Blank PDFs before 2001 and the stupidified graph after that.
They are empty apart from header and foot on my phone. I’ll check on the computer later.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.
Yes, but that is only tangentially connected with the questions at hand.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.
Ok, doesn't work on a phone for some reason.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.
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.
So according to the curves and best interpretation of them, Aviphot 200 is quite a bit faster in tungsten like light (?).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 (?).
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.
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