about the EXR and the VISION stocks

[L K Keerthi Basu]

Dear John,

 

I took a LAD for EXR and VISION stocks seperately for each color BLUE, GREEN ,RED. I found that Yellow is light in density then comperated to other two magenta and cyan in EXR. This yellow is little bit dark in Vision stock when compared to EXR. So from this I came to know You have Increased the yellow dye in the Vision stock, When we Increase the yellow more we will get more black in the print like what was followed in the offset printing tehnology.

Please Explain me am I right or wrong.

 

L.K.Keerthi basu

Edited February 1, 2005 by l.k.keerthibasu

[John Pytlak RIP]

Dear John,

 

  I took a LAD for EXR and VISION stocks seperately for each color BLUE, GREEN ,RED.  I found that Yellow is light in density then comperated to other two magenta and cyan in EXR. This yellow is little bit dark in Vision stock when compared to EXR. So from this I came to know You have Increased the yellow dye in the Vision stock, When we Increase the yellow more we will get more black in the print like what was followed in the offset printing tehnology. 

Please Explain me am I right or wrong.

 

L.K.Keerthi basu

<{POST_SNAPBACK}>

 

First, you do not expose a LAD onto each type of color negative film. You expose real pictures, or your own gray scale or gray card. Then, the processed negative is timed/graded by the lab on a color analyzer that has been set up with a LAD Control Film. Here is the procedure:

 

http://www.kodak.com/US/en/motion/support/....4.11.8.6&lc=en

 

A "normal" 18% gray exposure will usually have DIFFERENT Status M densities on the processed negative, depending on the film type. But these differences are taken into account by color timing / grading each scene relative to the LAD Control Film. Even if there are minor-to-moderate exposure/processing differences, the variation in the densities you get on the processed negative is usually less than the excellent latitude of modern color negative films, so you get very satisfactory images after color timing.

 

It is incorrect to call an 18% gray card exposure on your film a "LAD". It is correct to say that your gray scale or pictures were color timed or graded relative to a LAD, and that the lab used the Kodak Laboratory Aim Density control system to help control their timing, printing, and "curve placement" during duplicating.

[Dominic Case]

The red, green and blue densities of any part of a negative are due to the image-forming dyes (yellow magenta and cyan) and also due to the unexposed couplers which effectively form the "orange" masking colour.

 

Different negative stock types are indeed slightly different in formulation (it's what makes them different!). However, printer lights are adjusted in each case to make a balanced print so that - for example - an 18% grey card will print to a neutral grey colour.

 

Darker blacks can't be predicted from mid-grey density readings.

 

Offset printing technology is unlikely to be a useful source for explainign or understanding integral tripack photographic printing.

[L K Keerthi Basu]

Dear friends,

 

 

What I actually done is , We have a LAD negative In our Institution, With that I printed a LAD and I corrected it for the Perfect density of all colors RED,GREEN,BLUE ,BLACK,WHITE,GREY and lady's SKIN texture. After that I printed RED cutted the other two colors,like that I repeated the same for other two GREEN and BLUE. After processing the positive I found that the Blue sensitive layer or the Yellow dye is lighter then the other two colors and It is little bit darker in the VISION stocks this is the procedure which i have done. May I follow this as procedure. If it is wrong tell me.

 

L.K.Keerthi Basu

[L K Keerthi Basu]

Deaer Dominic,

 

First of all please tell me what is Latitude. How they define it, because most them explain me about SBR[scene brightness range] when they tell about latitude. Is it SBR and Latitude are all same, I think they are not. What I know is any type of film whether it is B/W or Color the latitude of them is 1 1/2 stops over and 1/2 stop under. But they say it is not latitude it is only printing range. Iam awating for the answer.

 

Thank You,

 

L.K.Keerthi basu.

[John Pytlak RIP]

Kodak has an on-line tutorial about tone scale and latitude:

 

http://www.kodak.com/US/en/motion/support/h1/structure.shtml

 

The average scene brightness range is about 160:1 (2.20 log exposure or about 7 stops). Of course some scenes have lower contrast, and others have higher contrast. The "latitude" or straight-line portion of the film must exceed the scene brightness range to capture the entire tone scale.

[Dominic Case]

After that I printed RED cutted the other two colors

If I understand you correctly, you have made three prints, each with just one colour exposed, to try to determine what is happening to each layer separately.

 

You are getting into quite complicated areas here: there is some degree of overlap in both the spectral sensitivity of each dye layer, and its absorbtion or density after processing. In other words, the blue-sensitive layer (for example) has some slight sensitivity to wavelengths closer to the green part of the spectrum as well as the blue part, and when it is processed, the yellow dye absorbs some green wavelengths as well as the blue wavelengths that it is meant to absorb.

 

Furthermore, the dichroics in your printer may not separate the colours perfectly: again, taking blue as an example, you might have some greenish wavelengths getting through the blue dichroics, and some blue wavelengths getting through the green dichroics.

 

All of these things conspire to make your test rather difficult to interpret. If you are seeing a difference in the printing behaviour of Vision negative compared with EXR neg, then it may be due to slightly different spectral characteristics of the dye layers in each stock: or it might be more complicated than that!

 

What exactly is it that you want to learn from your experiment?

[Dominic Case]

Deaer Dominic,

 

  First of all please tell me what is Latitude. How they define it, because most them explain me about SBR[scene brightness range] when they tell about latitude. 

 

This is really a different topic from the EXR/Vision one - but I'm not sure how to move it or jump threads so I'll follow John's answer here too.

 

Not everyone uses all these terms in exactly the same way. However, this is the way I do:

 

Scene Brightness Range is the difference between the brightest and darkest areas of a scene that you want to record. As John says, a typical average might be around 7 stops, but it can be more (or less!). There may be shadows that are deeper than that, but you aren't interested in the detail, so they can be disregarded.

 

Useful Exposure Range is the length of the straight line portion of the emulsion (or image capture device). Actually, it's a little longer, as the gentle fall off at both ends of the straight line is a great characteristic of film: that's what gives it such a great UER.

 

Latitude, as I have always used the term, is the difference between SBR and UER. So if a film emulsion has a range of 10 stops and your scene has 6 stops, then you have a latitude of 4 stops (the shape of the curve determines if it is 2 under, 2 over, or some other combination).

 

As John points out, if the SBR is greater than the UER (although he uses the term Latitude in this way) then you are in trouble: so if you have a 10-stop bright sunlight/deep shadow scene, it won't work well on a digital camera unless you use a lot of shadow fill. Conversely, if you have a flat, front-lit commercial shot of a white-tiled bathroom with pale grey towels, and a SBR of 3 stops, then Blind Freddy could expose it properly.

 

I've had a quick look through my bookshelf. Some people (as in John's reply) use the term Latitude to mean what I call UER. others support my definitions.

[L K Keerthi Basu]

Then I think this defination is right,

 

"When we over or under expose a subject still the withstanding capacity of the film to reproduce the image as that of the original scene brightness is know as film latitude"

 

I suddenly shifted to this topic because It struck in mind while Iam replying

 

L.K.Keerthi basu