B&W exposure latitude

fralexis said:

So it IS a good practice to shoot at one half the rated ISO? I'm also struggling at getting consistently good exposures. With my spot meter, I find it hard to determine what is middle grey in a landscape. I want to try just placing a dark shadow in zone III. Otherwise, I'll use my digital meter

Click to expand...

No, use the box speed and do what you are already doing. If all your equipment is properly calibrated and you are using the light meter correctly, one rarely needs to adjust ISO to get the full shadow depth.

Some people make a career out of continuously test and retesting file. Their time would be better used actually taking photographs.

fralexis said:

So it IS a good practice to shoot at one half the rated ISO? I'm also struggling at getting consistently good exposures. With my spot meter, I find it hard to determine what is middle grey in a landscape. I want to try just placing a dark shadow in zone III. Otherwise, I'll use my digital meter

Click to expand...

IMO the most reliable type of meter is an incident meter. Reflective measurement can be done Very well too but it typically requires more experience. As you have found, it requires judgement to pick the right point in the scene.

Adjusting to 1/2 box speed adds more safety factor but there are downsides to using extra as a blanket fix, like slower shutter speed, more grain, ... It is not a magic bullet.

Personally I incident meter and shoot at box speed and develop normally; systemic failures are very, very, rare doing this.

So, using an incident meter how is it used most effectively in the landscape? In my studio work, I aim the dome at the camera and meter. In a landscape I'm standing at the camera with no way to get to the subject a distance off. What methods seem to work best?

All you have to do is be in the same light, then you use it similarly to the studio.

If you aren't in the same light sometimes walking a few steps can get you there.

You can also do non-traditional measurements. If you are in shadow you will get a reading that will give you the equivalent of shooting at 1/2 or 1/4 box speed, for example. You can shoot there or adjust to correct, your choice.

BTZS is actually a zone system variant that uses incident readings normally, even preferentially for exactly what you are asking to do. I'm not suggesting you have to do that, just an example.

markbarendt said:

IMO the most reliable type of meter is an incident meter. Reflective measurement can be done Very well too but it typically requires more experience. As you have found, it requires judgement to pick the right point in the scene.

Adjusting to 1/2 box speed adds more safety factor but there are downsides to using extra as a blanket fix, like slower shutter speed, more grain, ... It is not a magic bullet.

Personally I incident meter and shoot at box speed and develop normally; systemic failures are very, very, rare doing this.

Click to expand...

I agree with Mark.

I would just add to remember that in high contrast situations (imagine a building which is half lit by full sun and half in shade) when using an incident light meter and a positive film you would take the measure by placing the light meter in full light (with the dome pointing toward the camera) while with an incident light meter and a negative film you would put the light meter in the shade (again with the dome pointing toward the camera).

Using an incident meter still requires to remember that with slides you expose "for the highlights" and with negatives you expose "for the shadows" when you have a scene in front of you with both zones in bright sun and zones in the shade.

Having said that, an incident light meter and "box speed" yields very good results in most situations, while spot metering is more prone to errors and I think is warranted only with high-contrast situations and slide film when you want to exactly understand the way the highlights will be rendered on slide film.

fralexis, I'm essentially doing what you suggest. I don't have a separate meter so I use my DSLR's spot meter for landscapes. When shutter speed permits, I follow Barnbaum's (The Art of Photography) recommendation of placing the shadows where I want detail into Zone IV at box speed - equivalent to placing them into Zone III at half box speed. This gives me some protection against under-exposure and has essentially no disadvantages since the film I use (Delta 100) has at least 2 stops more latitude for over-exposure than for under exposure (based on the characteristic curve measured by Michael R 1974) before hitting the shoulder. By over-exposing by one stop, I'm really just placing middle grey in the middle of the straight-line section of the curve, with about 4 stops dynamic range in both directions (8 stops total) before hitting the toe or shoulder. The shoulder is much more gradual than the toe so there is still some latitude for (even more) over-exposure. At the sizes I print, the grain from Delta 100 is negligible anyway, so I don't worry about the slight increase in grain from over exposure. Shadows blocking from under-exposure would be much more problematic. But note that I'm new to analog, so judge what I say accordingly.

Diapositivo said:

Using an incident meter still requires to remember that with slides you expose "for the highlights" and with negatives you expose "for the shadows" when you have a scene in front of you with both zones in bright sun and zones in the shade.

Click to expand...

I was lucky enough to find and read Dunn & Wakefield's Exposure Manual a while back. It gives various scenarios and the reasons for using various types of metering in them. Great text for anyone trying to figure out how to meter better, out of print but normally available used, I'd recommend the 3rd or 4th edition.

They actually recommend duplexed incident metering for slides, one traditional reading (mid-tone) is averaged with a light source (highlight) reading. I actually use this method for almost every shot I take and have yet to be disappointed at either end of the scale. Traditional incident metering (dome out) works just as well for front and side lit subjects, duplexing (flat faced/dome in) gains an advantage when the main subject is backlit.

BTZS pegs from the shadow incident reading and factors in a variety of other considerations including highlights similarly in theory to the Zone System. Both of these methods generally seek the minimum exposure which is a reasonable goal.

When I worked Zoning and Duplexed Incident side by side I found that there was normally little if any difference in the camera setting found, when there was a significant difference I'd recheck the the "zone" reading based off what the incident meter had told me and find where the incident meter was trying to put the shadow. Almost every single time I did this I found that the shadow placement was normally very acceptable to me.

markbarendt said:

I was lucky enough to find and read Dunn & Wakefield's Exposure Manual a while back.

Click to expand...

I bought a copy of that last year.

markbarendt said:

They actually recommend duplexed incident metering for slides, one traditional reading (mid-tone) is averaged with a light source (highlight) reading.

Click to expand...

And mentioned that in the similar thread we had at the time!!

Basically, it's using the incident meter at the subject and taking one reading pointing at the camera and one pointing at the light source and going half way between the two.

This only applies to incident meters with flat diffusers (if I remember correctly) as domed diffusers already take this into account by design.


Steve.

Yep, exactly Steve.

bxxxxxxxxxxb&wfilm is ver orgiving in tems of over exposurebut has little lstitude in terms of under exposure

andre,
welcome to analog. your method seems very sensible to me!

fralexis,

You are getting good, sometimes conflicting advice. Your interpretation of Ralph's charts on post #21... that it is OK to rate at half box speed... is a simple and effective way to assure adequate shadow detail and ease of printing.

More precise metering can provide you "better" negatives. Better being relative. Less grain (which today is not a common goal of analog photographers). Shorter, or more consistent print exposure times (which can make darkroom work more productive, again not a common goal today).

I use a 4x5 rangefinder which sometimes requires me to use full rated speed when handheld. But when I shoot landscape, I do not need the highest film speed because I am using a tripod and I love the aesthetic of water at slow shutter speeds.

RalphLambrecht said:

andre,
welcome to analog. your method seems very sensible to me!

Click to expand...

Thanks Ralph!

And thanks for the very informative illustrations you posted, especially the one showing the same scene photographed with over- and underexposure. It makes the point very effectively.

Another way to look at this is that your exposure latitude is a function of two things:

1) the contrast of the scene you are photographing; and
2) how many effective contrast grades of paper you have available to you.

At one end of the spectrum, let's say you are photographing a subject that has both whites and blacks that you want to render realistically, and that the white value is in sun, and the black value is in shade. Let's also assume that you are going to make a contact print, and that you have exactly one grade of paper (#2) and one developer (Dektol).

In this situation, you have very little latitude for error, either in exposure or development, because you need to render a full tonal scale, and the only tools you have available to you are, ummm... exposure and development. The difference between the low value in shade and the high value in sun is about 8 stops.

If you underexpose the negative, you'll lose important shadow detail just above pure black, and if you overexpose or overdevelop, you'll blow out your high values, and they'll be rendered without any tone or detail.

Now let's change the situation. The scene is the same, but it's now overcast, not sunny. The difference between black and white is now only about 5 stops. Furthermore, you're using a variable-contrast paper, and you have filters that get you from grade #0 to grade #5, and everything in between. On top of that, you have both Dektol and Selectol-Soft (or a Beers developer) that can also adjust the contrast grade of the paper you're using.

In this situation, you have a ton of latitude! Assuming you give the scene enough exposure to get the low values above film-base-plus-fog, you can be off up to three stops in exposure (or the equivalent in over-development), and still get a printable negative. The contrast of your scene is much smaller than your effective contrast grades in printing paper (effective = actual paper grades +/- those attained with soft/hard developers), so you can take your scene's tonal scale, and move it all over the place, or expand and contract it at will.

I agree with everyone else that, whatever latitude you have, it's on the "high" side. If you underexpose the negative, and there are "low" values in the scene that are important, then you're SOOL. If you overexpose the negative, then it mostly depends on the range of the important values in the scene.

It's for this reason (and the decline in the ability of modern films and papers to separate the low values in the scene from each other) that Fred Picker, late in his career, changed the way he determined proper exposure. Rather than expose for the low values and develop for the high values, he said "Place the highest important value on Zone VIII, and expose." That exposure placed the low values in the scene as high up on the scale as they could go, and he could then use the other tools at his disposal (mostly paper grades) to place the low values where he wanted them in the print.

mingaun said:

Ralph, thanks for those images which speaks very clearly.

Mark

Click to expand...

It iwill be well worth your while to get Ralph's book. Not expensive given the content. In fact probably the best "bang for buck" photographic book in the market place

pentaxuser

thanks, but i'm blushing now. Keep in mindthatsome individual chapters are available as free pdfsfrom my website.othes may be made availble upon request.