Edge efects with Pyrocat-HD

Photo Engineer said:

The bottom line is this. Edge effects are not good edge effects unless they do what is shown in the above post. Otherwise, the results will vary with magnification, leading to poor results, or what one wag described as "an optical delusion".

PE

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Ron,

Would the following statement be correct?

If the amount of micro-contrast is optimum for a contact print when the width of the edge effects is 40µ, the width of the edge effects would need to be reduced to 2.5µ with a 4X magnification to obtain the same micro-contrast.

Sandy

Sandy;

In this example, the height difference between lines and sizes is what is to be measured and the height difference with exposure at a given width is the micro contrast.

Therefore, the goal is not to match them effects at a given width, but to give the same visual contrast effect in a scene as magnification increases. As you increase magnification, you are aware that the flare causes apparent contrast to decrease. Edge effects tend to decrease this effect flare has on decreasing apparent contrast.

Measuring macro contrast is rather meaningless in most film comparisons unless one understands what is going on in the micro world.

PE

I agree that there is no such thing as "true sharpness" in a photograph. Some of the most striking photographs I have seen had no need of sharpness and would not really profit by any kind of sharpening. Such quality does not come under the purview of photographic technique. There are photos, to be sure, that depend on finely detailed representation for their full impact. It has been recognized for centuries that the ability to make use of surrealism and other "isms" is based on training in the representation of realism.

Photographers are more restricted than painters by the very tools they must use. Our eyes are autofocussing, scanning devices with a field of clear vision of less than 1 degree. Our cameras see much wider fields, but are ultimately limited by depth of clear focus. It can be a blessing or a curse. Selective focus forces the viewer of a print to see what the photographer considers to be the proper center of interest. Selective focus also forces the viewer not to see clearly the whole scene.

I see no reason why I must be expert in all possible uses of photography in order to form a preference of one usage over another and express my preference. I base my preference on results others have obtained as well as my own trials. I do not require anyone else to have the same preference.

..."At what magnification are those edge effects most likely to be apparent"..
I did some tests stand developing 35mm in Rodinal 1:200 90min 68F and on 10x enlargements the edge effect fades over about 1mm wide.It only works with some films,see my first post in this thread:
www.apug.org/forums/showthread.php?t=26327
Technically, it's easier to photograph a light gray card on top of a dark gray card if you just want to see the effect.

I have done simular close comparisons with stand and rotary development using pyrocat-mc and 400Tmax and 100Tmax and I must say I get what you seem to have shown on my monitor...not a great deal of difference. the rotary process in BTZS tubes is at least as sharp,film "etching effect" is about the same and the continuos slow wobbly tube rotaion gives very consistent repeatable results with pyrocat-mc and Tmax. What is gained in long stand development to my novice eyes hasn't quite materialized yet. However, I will keep looking. I with Jim Noel that the rotary negative seems to have greater resolution on my monitor also.

Show me some photos....

Photo Engineer said:

I'll have to agree with Patrick here. An unsharp mask is not the same as edge effects. In addition, edge effects or unsharp masks are difficult to judge or comment on unless you have comparisons without these effects to make the judgement with.
.....<snip>......PE

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With so much talk lately on APUG about unsharp masks, edge effects, accutance, adjacency etc, I would love to see the differences between these phenomena displayed using a series of photographs (rather than using many screens of dialogue and a few pretty plots to help me visualise things).

regards
Peter

Well, I have quickly become lost. I appreciate the comments regarding personal preferences when it comes to the appeal of potentially exaggerated edge effects. I'm still undecided about whether edge effects or even unsharp masking would appeal to me in terms of my own work. As of yet, I haven't experienced these effects enough to make a decision. I'm not fundamentally opposed to dramatic effects in pictures. They are just another tool that I would like to master someday. But, I agree that enhanced edges do not a good picture make.

In any case, from what I gather from this and the other thread that Alan mentioned, if edge effects are what I'm after, I'm getting the impression that I should be playing with the likes of Beutler, FX-1, FX-2, or Rodinal.

As for the sharpness of the print sections I posted, it may be correct that they are not as sharp as they could be. Or it could be that my scanner is crap. The print looks pretty crisp, but I've always heard that print materials are not meant to be enlarged to that extent. In other words, I think 1200 dpi may be beyond the limits of the paper. Nonetheless, I probably would have done better to use my other scanner.

In response to my original question, I getting the feeling that edge effects would tend to be more apparent in an image that has a lot of fine detail. Perhaps I should be looking for the effect in the grass rather than on the siding and door frame in the test picture, although I still don't see much there either.

Also, I question whether PL100 is even a good film to be looking for edge effects. Personally, I think TXP320 appears to be a much sharper film than PL100 with either Xtol or Pyrocat. Of course, that's just based on my experiences and subjective opinion.

PeterB said:

With so much talk lately on APUG about unsharp masks, edge effects, accutance, adjacency etc, I would love to see the differences between these phenomena displayed using a series of photographs (rather than using many screens of dialogue and a few pretty plots to help me visualise things).

regards
Peter

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Hey, me too! One thing I don't often see acknowledged on the web is the near uselessness of showing pictures to illustrate some point. Someone will say, "look at the tonal separation on this picture" or "look at how great this film performed" and yet converting a picture to a digital file sucks a good part of the information out of it. Sharpness is reduced to the resolution of a computer monitor and tones are translated into 256 steps. Even the scanner does an interpolation to arrive at what it calls pixels.

While I love how the web allows me to interact with folks who know more than I ever will, it still lacks the capacity for everyone to stand in front of an actual print and point to what they are talking about or press their nose (or a loupe) up against it and see minute details of grain, surface texture, sheen, and... acutance.

And you're right. I would love to see side-by-side examples that show the difference between two prints from identical negatives, one developed in rotary and the other in semi-stand. Or one developed in Xtol and the other in Pyrocat or Rodinal.

Photo Engineer said:

Sandy;

In this example, the height difference between lines and sizes is what is to be measured and the height difference with exposure at a given width is the micro contrast.

Therefore, the goal is not to match them effects at a given width, but to give the same visual contrast effect in a scene as magnification increases. As you increase magnification, you are aware that the flare causes apparent contrast to decrease. Edge effects tend to decrease this effect flare has on decreasing apparent contrast.

Measuring macro contrast is rather meaningless in most film comparisons unless one understands what is going on in the micro world.

PE

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In looking at the chart again there is actually very little difference in height between the 10µm line and the 100µm line. So If the height differnce in density is the important thing to look at in the chart I can understand why you don't see much difference in the final look unless you do something really dramatic in development.

In any even measuring micro contrast is something very few of us can do anyway, so from a practical point of view the most meaningful thing we can do is to compare results between different film/developers and types of agitaiton at the desired magnification and use the combinations that we like the most.

Sandy

sanking said:

First, I am not surprised that the negaive look similar. If they were developed for the same CI they should. However, to compare how they print adjust the exposure for contrast and print a small part of the two negatives at about 4X, then compare the difference. You should see greater apparent sharpness with the negative developed in minimal agitation. If you don't, try semi-stand with just iniital agitation and one more at about the half-way point of development.

Sandy King

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ref: http://www.kruegerphoto.com/edgetest.jpg

Sandy,

Maybe I'm looking in the wrong place for edge effects. Looking at the prints again, I think there is a noticeable difference in the grass which has a lot of fine light/dark detail. The minimal agitation print appears to have significantly higher contrast in he grass area on the print, even though the rest of the print does not seem to have much more contrast. Does that make better sense?

My extreme minimal agitation was for an hour at 68F. (1.5 minute initial rotary agitation with 2 inversions at 15, 30, and 45 minutes)

If I agitate initially and then only once half way through, what increase in time would you recommend? Should I still use the 1.5:1:200 dilution?

-Dave

sanking said:

In looking at the chart again there is actually very little difference in height between the 10µm line and the 100µm line. So If the height differnce in density is the important thing to look at in the chart I can understand why you don't see much difference in the final look unless you do something really dramatic in development.

In any even measuring micro contrast is something very few of us can do anyway, so from a practical point of view the most meaningful thing we can do is to compare results between different film/developers and types of agitaiton at the desired magnification and use the combinations that we like the most.

Sandy

Click to expand...

Sandy;

The height difference in the left data plot led to the contrast difference in the right data plot. So, in terms of actual contrast it is significant.

As for the rest of the comments, I agree that we don't have the equipment to measure this, most people don't understand it, and most people don't care. My point was, in the face of this and showing data, I showed this lack of interest and understanding. To properly work with these effects, the people striving to do it and perfect this technique must understand it.

To do this, you need to make comparisons.

That said, the bottom line remains, "If it works, use it. If you like it, use it" and anything else is rather meaningless.

PE

I dont know how to test adjency effect or accutance, but I found that my exactly shot, one develop with PMK pyro (agitations per 30 seconds per 5 seconds each) and the others develop with Pyrocat MC with minimal agitations 27 minutes (1 minutes initial agitations, and each at 21, 14, 7 minutes per 10 sec), dev in PVC tube with 5 minutes pre soak

I've found that dev with semistand sharper than PMK pyro in my 8x loupe

Dave Krueger said:

ref: http://www.kruegerphoto.com/edgetest.jpg

Sandy,

Maybe I'm looking in the wrong place for edge effects. Looking at the prints again, I think there is a noticeable difference in the grass which has a lot of fine light/dark detail. The minimal agitation print appears to have significantly higher contrast in he grass area on the print, even though the rest of the print does not seem to have much more contrast. Does that make better sense?

My extreme minimal agitation was for an hour at 68F. (1.5 minute initial rotary agitation with 2 inversions at 15, 30, and 45 minutes)

If I agitate initially and then only once half way through, what increase in time would you recommend? Should I still use the 1.5:1:200 dilution?

-Dave

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The increased contrast you are observing in the grass where there is a lot of fine detail where light and dark tonal areas meet is what I would expect.

To convert from extreme minimal agitaiton to semi-stand does not require much adjustment. Try about 15% more time for the semi-stand, assuming your time was correct for EM.

Sandy

Advantages of this method depend on format,maybe?
With practical 35mm photography I did not find the production of visible edge effects by stand developing Tri-X in Rodinal 90min 68F to be the best method to obtain apparent sharpness.The edge effects were too wide,1mm,and the film too grainy to compete with the orthodox Delta 100/T-max 100 in medium acutance developer.
I did not see any comments on 120.
In 5x4 it may better provide sharpness as the grain on the print is smaller and the edge effect only one quarter the width, about 0.25mm by my rough calculation,2lppm-close to the oft quoted limit of visibility 4-8 lppm.There seem to be a few reports this improved sharpness is the case.

Alan;

You have brought up another point that I was not going to discuss due to further complification. However, grain does affect the measure of sharpness and edge effect as image size becomes smaller.

Grain is a measure of average deviation in density over a given area. Thus the term RMS Granularity (Root Mean Square), or the statistical grain pattern. As the image becomes smaller, this value begins to be part of the measured edge effects, and affects the density of lines.

PE

Photo Engineer said:

Alan;

You have brought up another point that I was not going to discuss due to further complification. However, grain does affect the measure of sharpness and edge effect as image size becomes smaller.

Grain is a measure of average deviation in density over a given area. Thus the term RMS Granularity (Root Mean Square), or the statistical grain pattern. As the image becomes smaller, this value begins to be part of the measured edge effects, and affects the density of lines.

PE

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Ron, I seem to be having difficulty understanding the hypothesis of what you are stating. My misunderstanding arises from several statements that I understood you to make. You indicated that the edge effects were more pronounced in smaller film formats. And that edge effects were contributory to greater overall contrast.

Yet it would seem that from what you have indicated that as degree of enlargement becomes greater that the edge effects become less noticeable. For instance a 4X enlargement from a 4X5 negative would amount to an much greater enlargement from 35 mm negative. So for equal print size from differing sizes of negatives how can one make the statement that smaller film formats lead to greater edge effects? How does this reconcile within the framework of the statements that you have made?

Furthermore, it would seem to me that you are confusing edge effects with overall contrast. Given two negatives developed to the same CI but with differing developers and agitation regimen we know that edge effects can be much more pronounced in one of the negatives. How then can you say that edge effects contribute to greater overall contrast as in the second table that you posted earlier?

Given a certain line width on the negative, the edge effects ought to be the same. The developing process cannot know anything about the object space. Only the image space can have any effect. Thus, there will be a scale effect such that two lines which appear the same on the negative, including edge effects, will appear different when projected back to their respective object spaces.
The diagram provided by PE clearly shows the effect of line width on density of the developed image. This effect is independent of size of the negative. It depends on the absolute size of the image of the line. It doesn't know if it was produced by a 2" lens or a 12" lens.

Donald;

The result of edge effects in lines of decreasing width is increasing contrast between lines of different densities. This is due to chemistry.

Patrick has said it very well here.

You cannot compare reusults between negatives, but rather between objects magnified to different sizes on different negatives. And I don't just say any of this. It is a factual piece of process and film design that is accompanied by pages of mathematical treatment.

I'll be happy to post the math if you wish and the text of Mike's article, as he has given me permission to put it here, but you cannot copy it and distribute it, as you don't have that permission.

OTOH, there are many text books on film design that discuss this very fact and its impact on imaging.

PE

Maybe I missed it, but the influence of tanning of the gelatin and the resulting relief image has not been mentioned in this thread. I have noticed that of the family of Pyrocat XX developers, the MC seems to give the most noticeable relief image, especially the version without sulfite. I cannot tell with my limited resources if it is also the sharpest.

P-aminophenol, metol and ascorbic acid are all in the category of tanning developers to one degree or another. Sulfite is somewhat antagonistic to tanning IIRC. Any comments? Maybe someone will start a new thread.

gainer said:

Maybe I missed it, but the influence of tanning of the gelatin and the resulting relief image has not been mentioned in this thread. I have noticed that of the family of Pyrocat XX developers, the MC seems to give the most noticeable relief image, especially the version without sulfite. I cannot tell with my limited resources if it is also the sharpest.

P-aminophenol, metol and ascorbic acid are all in the category of tanning developers to one degree or another. Sulfite is somewhat antagonistic to tanning IIRC. Any comments? Maybe someone will start a new thread.

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Patrick;

Generation of a relief image contributes to forming edge effects by distorting the gelatin and forming a sort of gelatin 'lens' that effectively creates 'ears' on or around edges. This effect is seen in Kodachrome, not from tanning, but from the expansion of gelatin as the dye image is formed in the gelatin and it causes the gelatin to expand in an imagewise fashion.

That is one of the reasons Kodachrome images are so sharp.

It can be said that Kodachrome is the perfect example of two types of edge effects. One is introduced by the dye formation and the other is introduced in the classic manner by development byproducts such as iodide.

PE

gainer said:

Maybe I missed it, but the influence of tanning of the gelatin and the resulting relief image has not been mentioned in this thread. I have noticed that of the family of Pyrocat XX developers, the MC seems to give the most noticeable relief image, especially the version without sulfite. I cannot tell with my limited resources if it is also the sharpest.

P-aminophenol, metol and ascorbic acid are all in the category of tanning developers to one degree or another. Sulfite is somewhat antagonistic to tanning IIRC. Any comments? Maybe someone will start a new thread.

Click to expand...

Can you explain more about the "relief image" mechanism that comes with staining devlopers? I tried the MC, but didn't like it because the stain seems to have a color that tends to compress the highlight tonal range on my VC paper.

-Dave

[EDIT] Oops. I just noticed the post by PE explaining it...

You could try mixing a small batch of Pyrocat MC with hydroquinone in place of the catechol. The stain will be a different color which may or may not be more useful with conventional papers. Another ploy is to use pyrogallol in place of the catechol. You can use the same weight even though the molecular weight is greater because there are three active OH groups in pyrogallol but only two in catechol or hydroquinone. You will have three different colored stains. I think the colors are not only visibly different but also in the UV region.

On the subject of the surface relief, it can be quite pronounced. The first time I noticed it on PCat-HD negs I thought initially that it was damage to the surface. Since the emulsion is not a plane surface, I think that it must have a refractive effect. Is this part of the tanned neg sharpness (when a print is made, of course)? If so, would a condenser enlarger give a more marked effect than that of a diffuser one? I no longer have a condenser head, so I can't try it. I know that there is a contrast difference between condenser and diffused light sources too, so it might be hard to tease out what is actually happening.

- "relief image" mechanism... - Dave

Dave, take a sheet of film developed in a tanning developer (in this case one of your pyrocat negatives) and hold it up to the light so the emulsion side is showing. As you look at the surface, it seems the surface is "etched" by development. You will notice a very subtle difference in the way the light shows a sheen across this side, as it is turned from side to side. Basically, the emulsion shows a difference in thickness between differing density areas. As the light from an enlarger is projected through this film, it tends to "bend" a bit as it goes through these areas of differing thickness and density. This affects the way the light is projected through the film and onto the print. How much, you might ask? Some, I might reply. tim

noseoil said:

- "relief image" mechanism... - Dave

Dave, take a sheet of film developed in a tanning developer (in this case one of your pyrocat negatives) and hold it up to the light so the emulsion side is showing. As you look at the surface, it seems the surface is "etched" by development. You will notice a very subtle difference in the way the light shows a sheen across this side, as it is turned from side to side. Basically, the emulsion shows a difference in thickness between differing density areas. As the light from an enlarger is projected through this film, it tends to "bend" a bit as it goes through these areas of differing thickness and density. This affects the way the light is projected through the film and onto the print. How much, you might ask? Some, I might reply. tim

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Ah-ha! I have not looked at my pyro negatives yet to check this out, but the moment someone said kodachrome, I knew what to look for. I remember that relief appearance well back in the days of color photography (haha!).