Exposure questions for Negative films (Ver. 2)- Please Help...

[pankaj purohit]

Hellow friends, I am a FILM User and I have already posted a thread realeted to my this querry and I got some usefull

answers too but I think I wrongly composed my questions in that thread so I am reposting this recomposed post.

Please help me.

 

( Earlier Thread Link : http://www.photo.net/film-and-processing-forum/00QdI7 )

 

My question is all about the very basic thing of photography : EXPOSURE.

 

I don't say that I always got the wrong exposures or maximum time, but while exposng some imposrtant shots at

some important time, I got stuck with this basic thing - exposure and I went as camera meter said and the results

are not as good as I wanted.

 

I would like to ask my question in this manner :

 

A. >> Why we underexpose or overexpose...?

 

B. >> Is the overexposure helpfull for the contrasty, colorfull and grainless images ( I experienced so).

 

C.>> Where we should get the GRAY CARD reading : in sunlight, in shades, in dark shades (Assuming that all

situatons are in the scene to capture)..?

 

D. >> What will happen if I expose a paper printed with half black and half white according to camera meter, what

colors I will get.

 

E. >> What will happen If I experiment with black, and I expose the black color as camera meter, as overexpose this

by 2 stops and underexpose this by 2 stops (I know that underexpose to 2.5 stops down will render the black as

black).

 

F. >> If I overexpose the white by 2 stops and underexpose by 2 stops and one exposure as camera meter reading.

 

 

Please help me to understand again the exposure.... Thanks.

[steve m smith]

Your camera meter will try to expose each frame as an 18% grey equivalent. It was determined a long time ago that

18% was the standard for 'mid grey'<BR><BR>

If you use the camera's meter and take three exposures: one of a white card, one of a grey card and one of a black

card, the meter will try to give you three identical images - all grey.<BR><BR>

You can get underexposure if there is, for instance, a lot of sky in the frame and conversly, you can get overexposure

if there is a lot of shadow in the frame.<BR><BR>

You are on the right lines with your experiments with black and white cards. Bear in mind that a black card will

actually reflect some light and a white card will not reflect 100%.

A reading taken from the white card will have to be increased by 2 - 2.5 stops and a reading taken from the black

card will have to be reduced by 2 - 2.5 stops. A reading taken from the palm of your hand should be increased by

one stop. Weston light meters have a setting for this.<BR><BR>

The 50% white 50% black card will not work as the 'standard' mid grey is not 50% but 18%. Try a card with 18%

printed black and the rest white and see what happens.

[gerry297]

There is a great book that will help you with all of these questions called "The Confused Photographer's Guide to Photographic Exposure and the Simplified Zone System. It clearly explains all the exceptions to the exposure rules and what you must know to compensate for those conditions. The Author is Bahman Farzad. Amazon has it here: http://www.amazon.com/Confused-Photographers-Photographic-Exposure-Simplified/dp/0966081714/ref=pd_bbs_sr_2?ie=UTF8&s=books&qid=1219831172&sr=8-2

It was one of the best $20 I ever spent with a high $ to learn ratio. It will definitely help you correct those exposure issues you are struggling with.

[Ed_Ingold]

(a) We under/over expose (relative to an 18% grey target) in order to keep highlights or shadows within the capability of the medium. There is always a compromise as to which is more important (e.g., where do we need to retain detail).

 

(b) You will get the best grain and technical quality if the image is properly exposed (but what's "properly"). Slide film is often over/under exposed 1/3rd stop to decrease or increase saturation respectively. This technique has no relevance to negative film because you have control during the printing (reversal) step and a much wider dynamic range of capture.

 

© You can use a grey card in lieu of an incident light reading in any light, depending on what's important to you. That will render the grey card "neutral density" in the image - corresponding to Zone V. Actually you expect shadows to be darker than "average" and highlights brighter, so you would make adjustments to these measurements. Better yet, take spot readings of the subject to incorporate the actual reflectance of those areas and make a judgement (i.e. placement) for those exposures.

 

(d) You should get black and white respectively. Perhaps I don't understand your point.

 

(e) If you could get a truly black target, there would be no reflectance, hence the meter would peg at the bottom of it's scale. The proper technique is to measure shadow areas in which you would like to retain detail and lower the setting depending on the placement (Zone) you wish them to be. This is the typical priority for negative color and B&W film.

 

(f) A white target is somewhat useful, however problem areas in an image are likely to have specular reflections, which is whiter than white in a photographic sense. You probably have to accept blown-out specular reflections if anything else is important. In general, you would measure the brightest spot in which you wish to retain detail and increase (place) that exposure two stops. This is the typical priority for reversal (slide) film.

 

Anything you can read on exposure and the Zone System would be helpful. I would add "The Negative" and "The Camera" by Ansel Adams to your "must read" list.

[stwrtertbsratbs5]

You're not really under and over exposing. You're trying to make a correct exposure by accounting for the fact that the reflectance of your subject may not be the 18% gray to which your meter was calibrated. You could meter just a dark portion of your scene and adjust the metered exposure down to place it on the desired tone (2 stops down for dark shadows with detail). Or you could meter highlights and add 2 stops for light areas that still retain detail. You could, of course, meter both and discover that you can't simultaneously place both where desired. If you were shooting B&W, you would expose for the shadows and adjust development place the highlights as desired. Color, on the other hand, does not have that capability. So you'll need to decide which is most important. The old saying is, "Meter the hero."

[curt wiler]

The answer to © is pretty well explained in the Kodak gray card instructions or the Master Photoguide. In every

case an adjustment is required as noted above, but it should be realized that you cannot just read the card to

determine the exposure because it will NOT give you the correct exposure. Meters are not "calibrated to 18%". Per

Ansel's Zone System, 18% is the middle of Zone V, but that is not the reflectance of the average scene; it is

about 1/2 stop off. There are several discussions on Photo.net that have attempted to correct this myth, e.g.:

http://www.photo.net/casual-conversations-forum/00QMrP

 

The biggest problem with using a gray card for exposure, especially outdoors, is the surface sheen which itself

can add a half-stop in brightness, and then you need to make the adjustments for the average scene,

highlight/shadow readings, etc. It's a tough way to learn. An incident meter is much easier.

[swilson]

If you are getting your prints done from a lab keep in mind that what might look like an over exposed image could be the way they printed it.

It was not until I started scanning my own film and making prints from the scan that I realized just how often the labs mess up the print, or at the least the photo could have been printed much better.

 

If you have blown highlights in your print but the negative shows detail in the same area then it could have been printed to not blow out the highlights.

 

This is an example of a print I got back from the lab

Not only are the highlight way blown out but the image is soft.

This is what was on the negative

http://www.pbase.com/konascott/image/45161465/original

 

Unless you make your own prints, either with a enlarger or scanning, you won't really have control of how your prints come out.

 

Slides is of course different, it is all what you do in that case, unless the lab really messes up.

 

It is still important to understand how to properly expose you negative, but without control of the printing you are only getting half a solution.

[swilson]

Shoot I missed posting the scan of the lab's print, here it is.

http://www.pbase.com/konascott/image/45161464/original

 

And again from the negative.

http://www.pbase.com/konascott/image/45161465/original

[obakesan]

Hi

 

perhaps also you might find this approach to understanding exposure. Once upon a time people used both spot meters and then densitometery in determining exposure for printing, I've sort of come across a hybrid of this. Have a read of my page here (http://home.people.net.au/~cjeastwd/photography/film/digiExposure.html)

 

this might help you to understand what 'normal' exposure is. While grey cards and reflectance metering may eventually come to you in the mean time this method may be enough.

[obakesan]

Scott

 

looks like you might have set your black and white points a little tight on that negative scan. Its strange that a lab can print shadow details that you scanner cant get (considering the shadow details were in the thinest part of the negative where its easy to get at the stuff if a little noisy).

 

whats your scanner?

[swilson]

Chris,

 

The scanner is a Minolta DImage Dual Scan III, the scanner is ok but the software that comes with it is crap for negatvies. I have switched to Vue-Scan, which works much better but has its own issues. The photo is not something that I really care a great deal about so it is unlikely I will go back an rescan it.

 

What the Minolta software does is to scan the negative and then invert, makes sense, but when it inverters it will clip the dark areas, the more exposed parts of the image. The solution to to scan with a longer exposre time, now the highlight in the final image are ok, but the thin parts of the negative are blown, and so all the shadow detail is loss.

 

Before Vue-Scan I would scan the negatives as a slide and then do the invertion myself, it worked but was a fair bit of work.

[obakesan]

Scott

 

oke dokey ... no stress ... just wondered