Why Plus-X @ 80 & Tri-X @250 ?

[joe_nathan]

Hello everyone!

I'm pretty new to black and white photography, and I'm surprised to

know that

almost everyone rates plus-x @ 80 and tri-x @ 250. what is the benefit

of doing this? also, where would you find out the time tables for

developing the films in d-76 (1:1) at these asa ratings? I've shot

mainly on 120 film at the normal asa rating, and I've been thrilled

with the results!

thanks for your help.

[art_haykin]

Many shooters over overexpose negative films by up to a stop to get more shadow detail, and will process the rolls normally, depending on preference. If you are satisfied with your present results, then stick with them. The best test IS a test.

[jon_porter1]

Plus-X has beautiful tonality when exposed at EI 80 and developed in D76 1:1 for 75-80%

of regular time.

[jay ott]

The benefit is that by overexposing, you can have better control of the detail in the highlights in the development process. FYI, the term ASA has been replaced by ISO.

[joe_nathan]

Thanks for the info, everyone. Does this also apply to TX320?

[kelly_flanigan1]

Shooting B&W asa/iso film of asa 125 at 80; and 400 at 250 is not much "overexpsure at all"; it is 2/3rds a stop. Considering the accuracy of meters; apertures; shutters; the effect might not be noticeable to many folks; but noticeable to critical users.. A full stop overexposure for tri-x would be 200; a 1/2 stop would be 282; a 1/3 stop would be 320; a 2/3rd stop would be 250

[macgregor_anderson]

If you expose at a lower ISO and develop for normal time, your negatives will print lighter, with more detail in the shadow areas, and less detail in the highlights.

 

If you expose at a lower ISO and develop for a reduced time (tested so that your middle grey turns out middle grey) you'll get better shadow detail and the highlights will have only slightly less detail than normal.

 

By reducing development time, you are reducing the contrast of the negative. This is because shadow areas finish developing after only a couple minutes, while the highlights which have received much more light and therefore have much more developing to do, continue developing for longer.

 

Take a look at the shadow areas in some of your negatives. Are they virtually clear and unexposed? Would you like a bit more detail there? Is it bad enough that you can't pull any detail out in the printing process, even with a lower contrast filter? Even with dodging? Then you could consider shooting at a lower ISO. And you'll want to find a development time that keeps your middle grey areas looking middle grey. I'm sure you can find info online on this, but they are starting points. You'll be best off testing for yourself. I've done it, and it can be fun, if tedious. It's worth it if you are in the mood for that sort of thing. Plenty of books and also info in the archives to help you with this. Or I'd be happy to write down the procedure if you'd like. I'm no expert, and I might screw it up, but I'll try if you'd like.

 

So, it's done to protect shadow detail. And if you find you have problems with shadow detail that can't be fixed when printing, you should probably get testing. But it sounds like you are getting great results as it is, so I'd just keep shooting and enjoying until you get the bug to learn more. It's a slippery slope, and you might end up testing all sorts of combinations of films, developers, papers...you'll go broke and lose many friends. You'll also end up with negatives that look exactly like you expected when shooting.

[richard_cochran]

If you want the full answer, get ahold of a copy of

Ansel Adams' <cite>The Negative</cite>. If you want to

learn something for yourself, perform

the experiment in <a href="/bboard/q-and-a-fetch-msg?msg_id=008mLp&unified_p=1">this

thread</a>. That experiment was performed using

color film and a Frontier printing machine; the results

with Plus-X or Tri-X and a home darkroom or scanner will be

different.

<p>

Negative film tolerates overexposure much better than underexposure.

One of the benefits of rating a negative film at lower than

its manufacturer's rating is that you get a bit more "insurance"

to cover exposure errors. Whether you should develop such

film for a time less than, equal to, or greater than the

published time depends on what you want to do with the contrast and

highlights.

<p>

A very brief summary of Adams' <cite>The Negative</cite> is

"Expose for the shadows, develop for the highlights".

[steve_s.]

Joe, the answers above give very good information about why and when people sometimes choose to shoot film at a speed slower than the rated EI. I just want to say that not everyone does this. It depends on the developer you are using and what your intended purposes are.

 

I shoot at rated speeds or higher and use speed enhancing developers. I do this because I look to shoot people and street scenes, and speed is most important to me. I shoot HP5+ at EI 400 and develop it in XTOL. I believe Roger Hicks (a well respected author and contributor to this forum) has written that he shoots HP5+ at 500-640. If you did that in D-76 or other non-speed enhancing formulas, I think you might lose some shadow detail.

 

For FP4+, I follow Anchell and Troop's advice and shoot it at EI 200 and develop in FX-2. I did test shots at EI's over and under the rated speed of 125 and printed 8X10's to the same contrast. When examined with a loupe, I saw no loss of shadow detail at 200, so that's what I shoot. EI 200 is a great speed for most street photography and FP4+ is a great film.

 

To answer the second part of your question, I checked some of my sources (Anchell and Troop's "The Film Developing Cookbook," and The Massive Developing Chart at www.digitaltruth.com), but they don't show times for Plus-X or Tri-X at 80 and 250. At 400 for Tri-X, they recommend 10 minutes at 20 degrees C. I would recommend doing a clip test at 8, 9, 10 and 11 minutes and stick with whichever developing time gives you the negatives you like best.

[michael_goldfarb]

Not everybody rates the films slower. I have always shot them at their rated speeds and gotten great results in D-76 when printing on an Omega condensor enlarger. (And I'm talking thousands of rolls since the mid-1960s here.)

 

It's a highly personal thing, and some folks tend to be much more scientifically oriented about it than others... I would suggest shooting it both ways and deciding how it works on *your* equipment - you might find no particular advantage in rating it higher/lower than the specified ISO... Everyone's experiences seem to be pretty unique as far as this stuff goes.

[johnmarkpainter]

A HUGE variable in this whole discussion.....

 

Everyone interprets their Meter information very differently. A lot of downrating Film come

from people who shoot in Auto-Exposure modes or just basically shoot whatever the

meter is telling them.

 

jmp

[michael_goldfarb]

Some of us are even nuts enough to just guestimate exposure in classic manual cameras without light meters... and find that today's films (even the "finicky" TMX) have plenty of exposure latitude!

[nathan_dandar]

I actually usually shoot at the rated speed or higher. Most of the Tri-X rolls I make from my bulk roll end up getting shot at 1600. In fact, I spent all of Friday night wandering the streets shooting the old Nikon and an 85mm f/1.4 wide open with Tri-X at 1600 just to get shutter speeds of 1/15 to 1/30... FAR from ideal circumstances. Almost every one of the photos is completely usable, though. I guess it just depends on what you're going for. If the Canon 50mm f/1.0 wasn't so ridiculously expensive (especially now that it's discontinued) I'd buy one immediately because I do so much low-light shooting. For me, speed is usually king.

[Troll]

Because KODAK lies!