If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Film Q.
"Annika1980" wrote in message
... Remind me again ..... I just got a few rolls of Kodak Ektar 100. Everything I read says to rate it at either 50 or 64 instead of 100. If Johnny tells you to jump off a cliff ... (I'd rate it at 80 myself). That means I set my camera's ISO to 64. OK, so far. Now when I have the film developed do I have the lab develop it normally as if it was shot at ISO 100? Yes. What is the difference between doing this and shooting at +2/3 Exposure Compensation? Unless you're using some sort of data recording, the main advantage is convenience. -- Michael Benveniste -- (Clarification required) Legalize Updoc. |
#2
|
|||
|
|||
Film Q.
On 3/3/2009 12:31 PM Michael Benveniste spake thus:
"Annika1980" wrote in message ... Remind me again ..... I just got a few rolls of Kodak Ektar 100. Everything I read says to rate it at either 50 or 64 instead of 100. If Johnny tells you to jump off a cliff ... (I'd rate it at 80 myself). Doesn't the difference between ISO 50 and 64 fall well under the tolerance for inaccuracy in most camera's light meters? In other words, won't make any visible difference. For me, ISO 50 and 64 can be treated as identical for all practical purposes. Even 50 and 80 are pretty dang close (1 stop vs. ~2/3 stop difference). -- Any system of knowledge that is capable of listing films in order of use of the word "****" is incapable of writing a good summary and analysis of the Philippine-American War. And vice-versa. This is an inviolable rule. - Matthew White, referring to Wikipedia on his WikiWatch site (http://users.erols.com/mwhite28/wikiwoo.htm) |
#3
|
|||
|
|||
Film Q.
David Nebenzahl wrote:
Doesn't the difference between ISO 50 and 64 fall well under the tolerance for inaccuracy in most camera's light meters? In other words, won't make any visible difference. For me, ISO 50 and 64 can be treated as identical for all practical purposes. Even 50 and 80 are pretty dang close (1 stop vs. ~2/3 stop difference). It's true that shutters and light meters are often less accurate than we would like them to be, but I think the idea is to have a bias in favour of a generous exposure. Aiming towards a generous exposure of C-41 negative does three things for you. 1) It improves shadow detail. 2) It reduces apparent graininess. 3) It makes the film's latitude more useful. C-41 film has plenty of overexposure latitude, but little if any underexposure latitude. Peter. -- |
#4
|
|||
|
|||
Film Q.
On 3/3/2009 4:17 PM Peter Irwin spake thus:
David Nebenzahl wrote: Doesn't the difference between ISO 50 and 64 fall well under the tolerance for inaccuracy in most camera's light meters? In other words, won't make any visible difference. For me, ISO 50 and 64 can be treated as identical for all practical purposes. Even 50 and 80 are pretty dang close (1 stop vs. ~2/3 stop difference). It's true that shutters and light meters are often less accurate than we would like them to be, but I think the idea is to have a bias in favour of a generous exposure. Aiming towards a generous exposure of C-41 negative does three things for you. 1) It improves shadow detail. 2) It reduces apparent graininess. 3) It makes the film's latitude more useful. C-41 film has plenty of overexposure latitude, but little if any underexposure latitude. Yes. I routinely overexpose color negative film by 2/3 stop and seem to see all the benefits you listed. -- Any system of knowledge that is capable of listing films in order of use of the word "****" is incapable of writing a good summary and analysis of the Philippine-American War. And vice-versa. This is an inviolable rule. - Matthew White, referring to Wikipedia on his WikiWatch site (http://users.erols.com/mwhite28/wikiwoo.htm) |
#5
|
|||
|
|||
Film Q.
"Peter Irwin" wrote:
Aiming towards a generous exposure of C-41 negative does three things for you. 1) It improves shadow detail. 2) It reduces apparent graininess. 3) It makes the film's latitude more useful. C-41 film has plenty of overexposure latitude, but little if any underexposure latitude. The third point depends strictly on the manufacturers nominal rating as compared to physical response of the actual emulsion. There's no technical reason why a C-41 film exposed at the box rating couldn't have lots of underexposure latitude and only a little overexposure latitude. What is clear from looking at the curves of the Ektar 100 datasheet is that overexposure will tend to emphasize blues, contributing to an overall cooler exposure. That's why I suggest that people don't rely on generalizations and rate their own film to their own preference. After my own test roll (which included bouncing my F100 off a sidewalk), I found that 80 was the best compromise with my Nikon gear. -- Michael Benveniste -- (Clarification required) Legalize Updoc. |
#6
|
|||
|
|||
Film Q.
Michael Benveniste wrote:
"Peter Irwin" wrote: 3) It makes the film's latitude more useful. C-41 film has plenty of overexposure latitude, but little if any underexposure latitude. The third point depends strictly on the manufacturers nominal rating as compared to physical response of the actual emulsion. There's no technical reason why a C-41 film exposed at the box rating couldn't have lots of underexposure latitude and only a little overexposure latitude. Manufacturers rate the sensitivity of colour negative film according to the ISO standard. The speed of negative films is based on shadow sensitivity. All colour negative films of the same rating have the same shadow sensitivity within 1/3 of a stop (plus or minus 1/6 of a stop from nominal rating). There are few cases where Kodak gives a box speed which does not conform to the ISO standard, but when they do this they are careful to print EI rather than ISO. When Kodak says the speed is ISO then it is. All modern colour negative films have considerable overexposure latitude. Compare the H&D graphs for a 100 speed c-41 film and a 100 speed e-6 film and you will invariably find that the c-41 film stays reasonably linear to the right of the point where the e-6 film goes completely clear. What is clear from looking at the curves of the Ektar 100 datasheet is that overexposure will tend to emphasize blues, contributing to an overall cooler exposure. The three colours seldom (or never) track as perfectly as one might wish, but the overall balance in a colour print is always adjusted when printing. You do realise that each 1/3 of a stop increase in exposure is a shift of 0.1 units to the right on the graph. That's why I suggest that people don't rely on generalizations and rate their own film to their own preference. Absolutely. You should always do your own experimentation to see what works best for you. I will have to buy some Ektar 100 soon. The claimed Print Grain Index figures are especially impressive. If you look at the decade old figures for Vericolor III 160, you will notice that the claimed performance from 35mm Ektar 100 is comparable to the claims for 6x6 format vericolor III. Remarkable. Peter. -- |
#7
|
|||
|
|||
Film Q.
On Wed, 4 Mar 2009 16:09:27 +0000 (UTC), Peter Irwin
wrote: Manufacturers rate the sensitivity of colour negative film according to the ISO standard. The speed of negative films is based on shadow sensitivity. All colour negative films of the same rating have the same shadow sensitivity within 1/3 of a stop (plus or minus 1/6 of a stop from nominal rating). Take a look at the test results at this website and see if you still believe that: http://www.cacreeks.com/films.htm The 1987 ISO standard does not define speed by shadow sensitivity per se. It establishes density criteria instead. The standard merely codified existing practice -- as far as I know not a single color negative films had to be reformulated or rebadged in order to meet the 1987 standard. There are few cases where Kodak gives a box speed which does not conform to the ISO standard, but when they do this they are careful to print EI rather than ISO. When Kodak says the speed is ISO then it is. On a box of TMax-3200, what's the designation? Certainly in spec sheets, it's listed as an ISO-3200/36 film. They can get away with that because of the "recommended processing" loophole in the ISO specs. All modern colour negative films have considerable overexposure latitude. Again, the site I mentioned above disagrees. They give Ektar 100 only 2 stops of overexposure latitude, which means that if you expose it at an EI of 64 you'll have less overexposure latitude than underexposure. Superia 100 they rate at +2/-2. I will have to buy some Ektar 100 soon. The claimed Print Grain Index figures are especially impressive. If you look at the decade old figures for Vericolor III 160, you will notice that the claimed performance from 35mm Ektar 100 is comparable to the claims for 6x6 format vericolor III. Remarkable. Actually, I still have some frozen Vericolor III in 70mm. Assuming I can find anyone who can still process the stuff, I'd like to revisit it someday. -- Mike Benveniste -- (Clarification Required) Cogito eggo sum -- I'm thinking toaster waffles for breakfast. |
#8
|
|||
|
|||
Film Q.
Michael Benveniste wrote:
Take a look at the test results at this website and see if you still believe that: http://www.cacreeks.com/films.htm It is going to take more than the listed results from filmscan.ru to convince me that Kodak is rating their films inaccurately. The 1987 ISO standard does not define speed by shadow sensitivity per se. It establishes density criteria instead. The standard merely codified existing practice -- as far as I know not a single color negative films had to be reformulated or rebadged in order to meet the 1987 standard. The first ASA standard for colour negative films came out in 1965. The method of averaging the colour layers and the definition of the speed point have been rejigged since then but the changes were intended to be neutral for the majority of films. In other words, I would expect the results of the current method and the 1965 method to be very close in most cases. On a box of TMax-3200, what's the designation? From memory, it doesn't say anything about ISO on the box. I don't have a roll right now to check. Certainly in spec sheets, it's listed as an ISO-3200/36 film. I just checked. The PDF spec sheets say ISO 1000 in Tmax developer, and ISO 800 in D-76 and most other developers. Show me which spec sheets say ISO 3200. They can get away with that because of the "recommended processing" loophole in the ISO specs. Um, no. They can get away with saying ISO 1000 in Tmax developer, because the B&W standard no longer specifies a developer. It would be likely ASA 800 in the formerly specified developer. All modern colour negative films have considerable overexposure latitude. Again, the site I mentioned above disagrees. They give Ektar 100 only 2 stops of overexposure latitude, which means that if you expose it at an EI of 64 you'll have less overexposure latitude than underexposure. Superia 100 they rate at +2/-2. Take the negative film of your choice, either colour or black and white, do a series of exposures one stop apart until you get to ridiculous overexposures. See how many stops you have to go over before you get any actual highlight compression or other obvious overexposure faults. On the other hand, shadow detail will start to go with any level of underexposure. One stop over (derating by half) will almost always allow you to see details in the shadow areas better without causing any problems with the highlights. Increasing exposure will cause an increase in apparent contrast because you are moving the exposure off the toe. This may be undesirable in some cases especially if you are unable to reduce printing contrast slightly to compensate. I do not believe that the listed latitude ratings are meaningful. Peter. -- |
#9
|
|||
|
|||
Film Q.
On Thu, 5 Mar 2009 01:51:17 +0000 (UTC), Peter Irwin
wrote: It is going to take more than the listed results from filmscan.ru to convince me that Kodak is rating their films inaccurately. Then pick up some old film shootouts from the various photo magazines, or go shoot some and ask your lab to measure the densities for you, or talk to people who rate their own film, and see if they use the same EI for all films with the same ISO rating. Kodak isn't rating films inaccurately -- the spec is simply loose enough to permit them to choose the nominal rating. Don't believe me? Compare the characteristic curve of Kodak 400NC to that for Kodak Vision2 250D. My own experience with 400UC and 400NC show them to be at 2/3rds of a stop apart. Similarly, I rate Fuji 160S at either 125 or 160, but I typically rated Portra 160 at 100. In other words, I would expect the results of the current method and the 1965 method to be very close in most cases. Within 1/6th of a stop for _all_ existing films? Not very likely. On a box of TMax-3200, what's the designation? From memory, it doesn't say anything about ISO on the box. I don't have a roll right now to check. Certainly in spec sheets, it's listed as an ISO-3200/36 film. I just checked. The PDF spec sheets say ISO 1000 in Tmax developer, and ISO 800 in D-76 and most other developers. Show me which spec sheets say ISO 3200. You're right on Kodak's spec sheets, although they've been less precise in consumer ads. In their specifications tab B&H lists both TMAX-3200 and Delta 3200 as ISO 3200 films. Adorama does the same. http://www.bhphotovideo.com/c/produc...ecific ations http://www.bhphotovideo.com/c/produc...specifications Take the negative film of your choice, either colour or black and white, do a series of exposures one stop apart until you get to ridiculous overexposures. See how many stops you have to go over before you get any actual highlight compression or other obvious overexposure faults. Specifically with Ektar 100, I found an overexposure of about 2 stops was sufficient to blow out the blues, resulting in the dreaded C-41 cyan sky. And you? I do not believe that the listed latitude ratings are meaningful. Then please feel free to provide your own data or test shots rather than stating generalities. -- Mike Benveniste -- (Clarification Required) Cogito eggo sum -- I'm thinking toaster waffles for breakfast. |
#10
|
|||
|
|||
Film Q.
Michael Benveniste wrote:
On Thu, 5 Mar 2009 01:51:17 +0000 (UTC), Peter Irwin wrote: It is going to take more than the listed results from filmscan.ru to convince me that Kodak is rating their films inaccurately. Then pick up some old film shootouts from the various photo magazines, or go shoot some and ask your lab to measure the densities for you, or talk to people who rate their own film, and see if they use the same EI for all films with the same ISO rating. That's another question entirely. What is optimum to use is a different question from whether or not films are rated accurately. Film manufacturers always tell users to find their own optimum EI by testing, and say the ISO rating is only a starting point. Kodak isn't rating films inaccurately -- the spec is simply loose enough to permit them to choose the nominal rating. Don't believe me? Compare the characteristic curve of Kodak 400NC to that for Kodak Vision2 250D. Cine negative film speeds are covered by a different ISO standard than still negative films. Both will be rated to the nearest standard value to the measured speed. My own experience with 400UC and 400NC show them to be at 2/3rds of a stop apart. Similarly, I rate Fuji 160S at either 125 or 160, but I typically rated Portra 160 at 100. I bet that difference is to gain more contrast on the Portra by putting more of the exposure off the toe. Within 1/6th of a stop for _all_ existing films? Not very likely. From _Photographic_Sensitometry_ by Todd and Zakia (1974 ed) p.162 "Manufacturers' published speed values necessarily include some tolerance. Thus an ASA Speed value of 64 represents in fact a range of speed values. The present standard permits a total range, at the time of testing, of 1/3 of a stop, so that a film rated at 64 could have a tested speed between 57 and 71." "Beyond this tolerance, any given sample of film will, by reason of its age and usually unknown storage conditions, have an effective speed perhaps considerably different from the value obtained when it was tested." You're right on Kodak's spec sheets, although they've been less precise in consumer ads. In their specifications tab B&H lists both TMAX-3200 and Delta 3200 as ISO 3200 films. Adorama does the same. Neither B&H nor Adorama make film. I haven't seen anything actually from Kodak which claims 3200 as the ISO speed. Specifically with Ektar 100, I found an overexposure of about 2 stops was sufficient to blow out the blues, resulting in the dreaded C-41 cyan sky. And you? I haven't used Ektar 100 yet. I don't doubt that you saw what you describe. I do doubt that it had anything to do with overexposure. I think it highly probable that this is a side effect of moving the shadow values up off the toe thus increasing the overall contrast with the result that the same printing contrast didn't give enough room on the paper for the highlights. Then please feel free to provide your own data or test shots rather than stating generalities. My three generalities were useful, and were things I did not know when staring out. With colour negative film - a small increase in exposure gives better detail in the shadows - a small increase in exposure results in a decrease in apparent grain - a small increase in exposure reduces the risk of underexposure and that the risk of underexposing negative films is greater than the risk of overexposure thus giving more useful latitude. I should also have noted that increasing exposure increases the contrast in the shadows which can sometimes have undesirable consequences and that increased exposure also makes film very slightly less sharp, although this is scarcely noticeable unless you go seriously overboard. Peter. -- |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Negative print film vs. Slide film differences at current/present time? | Progressiveabsolution | Medium Format Photography Equipment | 18 | July 10th 06 02:08 PM |
Is there a decent film scanner for 6x4.5 medium format film $500 or less? | Rick Baker | Digital Photography | 6 | March 17th 06 02:22 PM |
Any camera/film stores carrying 120 film in or around Hilo, HI | Norm Dresner | Medium Format Photography Equipment | 22 | April 11th 05 07:56 PM |
WTB film holder for Polaroid 8X10 Film Processor Model 81-12 | jp | Large Format Equipment For Sale | 0 | April 5th 05 04:54 AM |
Advice for camera bag, film developing and film choice | JZ | 35mm Photo Equipment | 4 | August 24th 04 08:56 PM |