How to evaluate BW negatives...

[peter_kim2]

Ive kinda asked a similar question before and got a lot of helpful

responces but I have a specific one this time.

 

How can you tell if your negatives are over exposed or over

developed and conversely under exposed or under developed?

 

I have recently gotten back into developing my own film after a long

time and have been getting very dark (dense?) negatives developing

Tri-X in Xtol using the posted standard times at 9 minutes at 1:1

and 68 degrees. Standard development...30 seconds continuous

agitation at first and thereafter 5 seconds every 30 seconds.

 

I wonder if I should up my personal ei for tri-x from 400 to

something like 640 as xtol seems to have a reputation as a speed

increaseing developer...or if I want to keep shooting at 400 then

just decrease development time.

[marc_leest1]

The easiest way to judge negatives is to make technically correct contact prints. If a contact print looks good the neagtive will print ok in the enlarger.

[amul]

I personally use a standard agitation of first 30 seconds, and then the last ten seconds of every minute, including the first, and the last ten seconds if the last period is a partial-minute. But I know people who use your system, too. I just think my way feels like less work.

 

Overexposed: negative has no detail in the dark parts, which will be the highlights on the print

 

Underexposed: no detail in negatives light parts, or shadows on the print

 

Overdeveloped: you're only in a real problem area if the imprinted text in the grooves starts to bleed

Underexposed: you're only in real trouble if the imprinted text in the grooves isn't clear.

 

If that isn't clear enough, get a strip of professionally developed negatives and compare color and density.

 

If you're following the times posted in the fact sheet and maintained temperature control within the specified parameters, then you're better off maintaining your development practices and improving what you get out of your negatives by improving your actual exposures.

[m0002a]

Marc is correct. Make prints that are exposed in the enlarger for the minimum time it takes to get maximum black through the film edge. </p>

 

What is minimum printing time to get maximum black? When you have a print that includes the blank film edge and some that includes no film at all (like sprocket holes), and you cannot see the difference between the clear part of the film and part that contained no negative at all. Such a print must be thoroughly dried to make the proper determination. Then remake the print (without the film edge) using that same �technically correct� exposure time. </p>

 

They only difference I have with Marc, is that contact prints will work fine for diffusion enlargers, but for condenser enlargers you should enlarge the prints to make sure and get the same contrast. </p>

 

Don�t be concerned about a slightly overexposed negative. </p>

 

Also, I have seen some books on photography that show examples of all 9 possible negative conditions. You might be able to find such a book in a public library.</p>

 

<ul>

<li>Normal exposure, Normal development

<li>Under exposure, Normal development

<li>Over exposure, Normal development

<li>Normal exposure, Under development

<li>Under exposure, Under development

<li>Over exposure, Under development

<li>Normal exposure, Over development

<li>Under exposure, Over development

<li>Over exposure, Over development

</ul></p>

As one can see, some degree of technical expertise is needed for B&W photography to ensure consistently good results, because the changes of one getting �lucky� are slim.

[hans_beckert]

What format are you using? What kind of enlarger?

[jay_de_fehr]

I'm with Marc and Mark. Do the max black paper test to determine your basic printing time, and then contact print your negatives. Also keep in mind that exposure affects the low values and development affects the high values (an oversimplification, but useful for your purposes). Adequate shadow detail suggests adequate exposure, and detail in the highlights suggests proper development. Your contact prints will tell the tale. Good luck.

[stephen_benskin]

Using the standard printing time technique keying on paper Dmax is not only problematic but flawed. The shape of the shoulder of different paper curves vary causing the relationship between the paper Dmax and the point of just noticable difference to also vary. This is not an ideal situation for standardization.

 

A better way is to use 90% of the paper Dmax as your standardization point. If you don't have access to a densitometer, it is usually the point of just noticable difference in density from Dmax. This will be your paper Zone I. Just remember to do the test using a negative with a density of 0.10 above Fb+f.

[lex_jenkins]

There have been several nearly identical questions asked recently. If a quick search doesn't turn them up easily perhaps another forum member can point them out for you. (I'd do so myself but I'm swamped lately with family matters.) It's a perfectly reasonable question, one that confronts all of us early in our progress. Good luck.

[bob haight]

Study the negative on a light box and look for details in the darks and lights. If a significant shadow detail is clear you know you underexposed and vice versa. Unfortunately, those great sky details in a neg are usually on otherwise underexposed negatives. You will see this in a maximum black contact print. If you are getting dense negatives, first guess is a lot of exposure.

 

An easy test to rate the film to your developer and meter is to set up a gray card in even light and calculate zone 5, the meter reading. Then close down to Zone 0, six stops less light and open up half stops if possible back to zone 5 and then expose the rest of the film at zone 5. Process and run a correct contact print. From this you will see where Zone 2 ( first hint of gray) appears. If not your Zone 2 you can probably decrease film speed accordingly. Then if Zone 2 falls into Zone 2, look at the Zone 5s. These should match a gray card. Fix your Zone 2 first then play with developement times, 20 percent more then less until later rolls Zone 5s match up to the gray card.

Really not much trouble but sure can give you your times for your meter, your agitation technique, and your developer.

[peter_kim2]

Thank you for all the answers. So the easiest way untill I learn to eyeball my negatives it to print a contact sheet until the edges are just completely black then evaluate the frame for correct exposure range? If I have blown out highlights or no shdow highlights its an exposure problem...if everything has uniformly blownout shadows 'and' highlights then its a over/under devlopment problem?

 

Bob abd Steven, I have yet to master working with the zone system, I'm still a (re)beginner. Lex I'll besure and try a more concentrated search of the back posts. I did imagine there would be similar questions, I guess I didnt look hard enough.

 

Hans, your answer are always very helpful I look forward to hearing from you. I'm using 35mm tri-x in a standard paterson tank. I use the local rec center dark room so I dont know what kind of enlarger it is. If it helps its a rather old looking Omega with the regular slot of adding filters.

[hans_beckert]

May we assume you are working in 35mm?

 

Evaluating negatives can come only from printing them, and with reference to specific criteria. For instance, many experts affirm that using a slightly harder paper (grade 2 1/2 - 3) and a slightly softer negative (than are used in sheet film) are the keys to successful 35mm work. Without reference to such a 'normal' contrast grade, your film development cannot be zeroed in properly.

 

In other words:

 

Develop your film so that most of them print properly with grade 2 1/2 to 3. That is the criterion. Once you have succeeded in doing this, then learn to recognize the negative that will print properly with grade 2 1/2 to 3.

[bob haight]

Peter, the test I set out requires only knowing a gray card is the middle tone, or Zone 5 and the first hint of gray is zone 2, you should be able to easily see this and run the simple math from 2 to 5. An extensive knowledge of the Zone system is really not needed. What is nice to know is that the low values tend to stay the same no matter how you develop so its nice to set the meter for them. The high values, light values change with development times and learning this allows you to adjust contrast to your scene and printing. Really, what your doing is learning how to develop for a certain density and matching up to a graycard is a good way to do it, once you know your films speed based upon your meter and developer.

[ricardoyamamoto]

What I have been told is that the exposure number and film code written along the edges of the film should be consistent black (for black and white films) when you look at your developed film on a light table.

 

If it is not solid black, it means it is under developed. If it is so strongly black that the numbers and codes get edges, it is overdeveloped.

[tim_curry]

I do film tests based of Picker's book "Zone VI Workshop" and find it is easy to understand and use.

 

Another good tool, if you don't have a densitometer in your back room, is the simple Stouffer zone strip. It is simply a small strip of paper which was exposed to varying light intensities and gives values for zones 1-9. If you use this in conjunction with your tests, it will make things much easier to judge values you want in a print. Cost is about $12.00 (US) and worth every penny to help get you started.

[steve_s.]

Peter, you have already gotten a lot of great advice in this thread. I have only two points to add. First, Mark's idea of looking at a book with examples of the 9 possible negatives is a good one. There are several out there, I like Les McLean's book, "Creative Black & White Photography." He includes pictures of 4x5 negatives. You can see for yourself in his examples what it means to have an underexposed negative with little shadow detail. He also shows prints of the 9 negatives. I have learned a lot from his book.

 

Second, show your negatives to professional photographers in your area. They will show you things that you wouldn't see yourself at first.

 

Good luck.

[james_megargee]

Peter, You have gotten some good info here. But let me add one (I believe)

important bit. Knowing if you should be setting your ISO at 400 or 650 or

whatever is only a reference point. Correct though it may be. The more

important issue is "where and how" are you taking your readings from within

the scene. For example, even if you have determined your correct ISO and

just point your meter into the shadow area for your exposure reading, then

you are exposing your shadows at Zone 5 and generally overexposing that

area. Without seeing your negatives its hard to give specific advise but it

sounds as if they are first overexposed, which would normally require that

they be under developed. And since you have developed them at normal

time, etc. they are then more than likely also overdeveloped.