6x17/Focus/Exposure/DOF Methodology

[cwb_.vt]

Hello,

Recently purchase Horseman 617 with 90MM. Wonderful Instrument.

 

All my previous experience has been with 35MM and MF TTL meters and

focus (Spotmatic, FM2T, M's, R's, 67II, D2X). Enthusiastic amateur,

shooting static landscapes (main subject tends to be 50 plus feet away,

Vermont things, barns, hills, streams, etc..95% of time on tripod). With

6x17, always on tripod (slide film and B/W).

 

Usually I am able to use Thom Hogans charts for Hyperfocal distance or

from DOFmaster.com or the lens (I know this stuff is on some lens, but I

always forget how to work it...if may be on this lens, but I may not know

how to read it..this is my fist LF lens). But with this camera, I am not able

to really find charts. I tend to shoot at F16 to F22 only because they are

not near the extreme and I look for "good" DOF in my landscape

panoramas. To get "good DOF", I have just been setting the focus at 15 to

30 feet as the panarama may "start" at 50 feet or so. Although still

making the big mistakes as I learn this camera, my DOF results have

been fine and I could go on shooting like this. Questions...

 

1) I there a set of charts that I could use that I could say at F16, the

hyperfocal for this lens is "x feet", at F22 it is "y feet"...is this somewhere or

am I making it too complicated?

 

2) At F16 and F22, and the center ND filter and perhaps a polarizer, my

exposures as measured on light meter may exceed one second. So, I

count and hold the cable release open. Is there a tool or timer that is

more exacting? Something I can attach to the release and set it at say 2

seconds and I will be open for two seconds (set to B). I searched on

B&H and found only those times that lag the shutter so you can run and

get in the photo.

 

3) This is the first time I have used a hand held light meter. Since it is

summer and most of the images have some sort of green (my 18%) in

them, I measure this and add some filter adjustments and bracket. I am

getting better. With only 4 images per roll, I would like to get to two "trys"

per image. But as the seasons change, the Green (or my 18% gray) will

go away....I guess this question really boils down to how do you effectively

use the zone system...do you always search for some 18% gray, or do you

look for other zones and adjust...or is it just experience....I do not have the

confidence that I could measure and take an image of a sunset with the

6x17 and a handheld....where is the 18%?....how do you measure the

morning light and mist on the pond?...how do you measure the sunset

over the lake?....

 

I have ready many books and I "think" I understand, I am just not sure how

to apply when my 18% green is gone.

 

thank you for your time on my behalf

 

Chris

[ellis_vener_photography]

great and beautiful camera. Congratulations.

 

1.) You can do some tests and make your own accordign to your definitons of what you

consider in focus enough: not everyone's tandards are goignto be thesame and this is

related directly to how large the final print will be and the typical viewing distance forthat

size print.

 

2.) Use a Radio Shack stop watch or a digital wrist watch. For exposures longer than 2

seconds, set the shutter to "T" for exposures longer than 2 seconds. when the shutter

uses the T setting, you click once to open the shutter and once to close it.

 

3.) More importantly than finding something that is 18% gray look at the spread between

the readings of areas with highlight detail you want to record and the areas of shadow

with detail that you want to record. If this spread is larger than say six stops decide which

it makes sense to sacrifice given the scene in front of you and your expressive intent. As a

general rule, you want to retain highlight detail.

[the moderator doesnt lik]

Acceptable DOF is dependent upon degree of enlargement, and of course personal tolerance for fuzzies. If you enlarge 10x, for example, you should choose a pessimistic circle-of-confusion (CoC).

 

For example, if I have to enlarge a 6x6cm to 10x, I use the CoC commonly acceptable to 35mm format. (Hasselblad once published exactly this recommendation pertaining to the hyperfocal scale of their SWC camera, saying that the scale on the lens was not to be considered for serious enlargements.)

 

The DOFMASTER informat is helpful. Useit. http://www.dofmaster.com/doftable.html

 

If you images are not sharp enough, and everything else about your technique is good, try the COC setting of a smaller format, for example 6cm (your vertical dimension). If it's still not sharp enough, change the subject distance.

 

After you've made a hundred images you will know intuitively how to work it.

[leonard_evens]

1. Once you know the hyperfocal distance at one f-stop, it is easy to find it for another. Just multiply the known hyperfocal distance by the ratio of the two f-numbers. For example, suppose you know the hyperfocal distance at f/16 is 12 feet, and you want to find it at f/22. The ratio is 16/22 = 8/11, and if you multiply 12 by that, you get about 8.7 feet. As another example, suppose you wanted the hyperfocal distance at f/8. The ratio would be 16/8 = 2, so the hyperfocal distance at f/8 would be 2 x 12 = 24 feet.

 

But see below for a comment about DOF calculators.

 

2. For exposures longer than 1 second, I just look at my watch or count. The point is that you don't have to be that precise. But if you are concerned, probably the easiest thing to do would be to get a watch or other electronic devide which beeps at you once per second. There probably are devices that do what you decribe, but they are unlikely to be worth the cost.

 

3. There are other Zone V references if that is what you want. On a clear day, the sky high up is one such. If you do some experimentation, you can probably find others. You could also use an actual gray card, but then you have to be very careful how light falls on it.

 

But using Zone V to set exposure is not really what the Zone System is about. You have to consider different elements in the scen, see what the exposure values are and relate them to what you expect in a final print. The usual recommendation for b/w photography is to set the important shadows on Zone II or (more often) III to determine exposure. You also record where other parts of the scene fall. You can then adjust negative development so that those values fall in appropriate Zones when printing on normal paper. You can't do this for transparencies. In that case, you might expose instead so that a highlight is on your preferred Zone (say VII or VIII) and let the shadows fall where they may. Often you will end up with underexposed shadows, but that is usually preferable to washed out highlights. For color negative film, you have some more freedom than with transparencies. If you scan and work digitally, you can adjust contrast for color images as well as b/w. But this is really going too far afield. I can't summarize all sublteties of the Zone System in a short paragraph.

 

I'm not familiar with Thom Hogan's charts, but there are lots of online DOF calculators. For example,

 

www.largeformatphotography.info/tools.html

 

has links to several. Most of these will also calculate the hyperfocal distance.

 

The important thing is that any you use should allow you to enter a value for the circle of confusion (coc). That parameter is a specification for how much fuzziness you are willing to accept while still considering the image sharp. Its size depends on the format and what you expect to do with the images. It is really a personal choice. My guess is that for 6 x 17, it might be safe to start off with a value of about 0.1 mm and see how that works out for you. You can then increase it or decrease it as appropriate.

[paul.droluk]

Each lens has it's own unique helical focus mount with the DOF marked for the particular

focal length. I find using this much quicker to use than consulting a table. In the 90mm

example attached apertures (f-stops) are marked on the top most ring, and the distance

scale is marked on the focus ring (which rotates during focussing). Shown focussed to 20

feet, simply look at the f-stop markings for a given aperture value before (to the left) and

beyond (to the right) the red focus distance mark. Directly below (on the distance scale) of

the f-stop markings are the distances (before and beyond) that would be the boundaries

of your effective DOF. In this example when focussed to 20 feet, the DOF @ f22 is from 10

feet to infinity. At f8 (focussed to 20 feet) the DOF is from 14 to 30 feet.

 

The only caveat to this is knowing at what COC the DOF scale was calculated. If you find

using the scale "as is" doesn't yeild sharp enough images for a given print size, then drop

down one or more f-stops when interpreting the DOF scale on the helical focus mount. For

example use the f16 markings (on the DOF scale) if you're actually shooting at f22... this

effectively decreases the COC employed in the calculation.<div></div>

[paul.droluk]

Here's another example showing the HFM focussed at infinity, a mistake newbies can make.

When focussed to infinity you can easily see that a large portion of the effective DOF is "lost"

beyond infinity. The DOF is only from 20 feet to infinity @ f22, rather than 10 feet to infinity

@ f22 when focussed to 20 feet (shown in the previous example).<div></div>

[leonard_evens]

Paul,

 

Your comment may be helpful for 35 mm and most medium format photgraphy. But lenses for the Horseman 617 don't generally use helical focusing and hence don't have DOF scales on the barrel. I haven't looked at a 617 closeup, but I would be very surprised if focusing were not done by moving the board to which the lens is attached closer to or further from the film plane.

 

Even for fixed lenses in smaller format cameras, the use of the DOF scale on the barrel can be misleading. As a couple of us have noted, DOF estimates are based on a choice of maximal acceptable circle of confusion. This is generally smaller for smaller format and larger for larger formats. It is also dependant on how images made from the camera are going to be used. If you expect to make large prints which people will view closely, you will want to use a small coc. If you expect people to stand well back, then you can get away with a larger coc. The DOF scale on the barrel of a lens is based implicitly on a choice of coc, which may or may not be appropriate for the way the lens is used.

[paul.droluk]

Leonard... in fact the Horseman 617 camera does use helical focus mounts for all of their

lenses, but I don't know what COC they selected to calculate their DOF scale. A well designed

and well executed HFM with an accurate DOF scale will be very accurate. At Fotoman we

elected to use a COC of .51 (commonly used on DOF scales for 6x7 lenses). As our smallest

format camera is 6x12, the .51 COC would be considered "conservative". More so as the

format size increases, and we use the same .51 COC for all of our cameras right up to 8x10.

Of course reproduction size and viewing distance have a great effect on what COC one

should choose, but using a stop or two less than indicated on a given DOF scale is no

different than choosing a smaller COC... in practical terms.

[leonard_evens]

Paul,

 

Sorry about my ignorance. I was using the information at

 

www.photografica.dk/images/news_upload/SW617e.pdf

 

It lists standard Schneider large format lenses. Are these special versions that Schneider makes for Horseman? Or do they enclose each lens in a helical mount with its own DOF and distance scales appropriate for its focal length?

[paul.droluk]

Leonard... I'm uninformed as to who actually produces the HFM. I would think Horseman does

as the HFM they are using on their 617 doesn't look like either the Schneider or Rodenstock

HFM. Traditionally Horseman has done their own mounting of lense (re: 612 PRO).

[darcy_cote]

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For answer #3

 

Pick up a copy of John Shaw's Nature photography field guide