One frame developed as a positive image HP5+ ????

[will_crankshaw]

<p>Has anyone ever had a frame come out as a positive image on a roll of negative film? I developed a roll of HP5+ 120 film last night in Caffenol. The first frame caught my eye as being a little unusual looking. When I looked closer I realized it was developed as a positive. The following two frames were the same image, but in negative. I've tried to search online, and it doesn't look like there is anything out there unless I'm just using the wrong terms to search.</p>

[Mike Gammill]

<p>Does this frame appear positive regardless of how light passes through it or does it have to be held at an angle? I've noticed on black & white negatives that are moderately to severely underexposed that holding the negative up to the light at an angle sometimes produces that effect. I don't know if that would be easy to show online though.</p>

[will_crankshaw]

Good question. I haven't had a chance to scan them, but I noticed this looking straight through the strip

with back lighting. It didn't seem to change based on angle, and was distinctly different from the adjacent

frames at the same angle. I'll have to scan them tonight for a definitive answer on whether it's actually

positive.

[User_5888660]

<p>Is the frame that appears positive quite a bit thinner than the other two? A thin negative will sometimes look like a positive, depending on the viewing light. </p>

[lex_jenkins]

<p>It may be a type of chemical fogging, silver stain or dichroic.</p>

[will_crankshaw]

<p>Lex - Does that mean it could actually have ended up as a positive image? Would you be able to point me to some reading about those things?</p>

<p>Edit: I'm reading connections between table salt used in caffenol recipes with dichroic fog referenced quite a bit. This would fit my situation, although it still seems strange to me that it is only one frame.</p>

[will_crankshaw]

<p>Now that I'm home, I noticed without backlighting it looks like a negative, and is probably somewhat underexposed. With backlighting it becomes a positive image. I'm assuming one of the previously mentioned issues is the answer, just not sure which.</p>

[SCL]

<p>It is a phenomenon typical of underexposed negatives when light hits the emulsion in a certain fashion. If you underexposed a whole roll and viewed the negatives so light reflected from them at a particular angle they would appear as positives. Nothing new or unusual or related to your developer.</p>

[will_crankshaw]

<p>Very cool. I had never read about this, or really noticed it before. Thanks for helping me figure this one out.</p>

[James G. Dainis]

The basics behind tintypes and ambrotypes is, a thin underexposed negative placed on a black background will appear as a positive. I have noticed that an underexposed frame on a roll of film will look like a positive.

[James G. Dainis]

I forget what I did wrong here; this negative was made many year ago. I suspect the flash wasn't firing. But it shows how a thin negative can look like a positive.<P>

<center><img src="http://jdainis.com/pos.JPG"></center>

[owen_omeara]

<p>Will.</p>

<p>I used that exact film in 120 size for 10 years and never had that happen. Let us know when you solve the mystery.</p>

<p>-O</p>

[murray_kelly]

<p>Will, you don't say what camera you were using. I wonder, because Kodak Rapid Process Copy Film will give you a positive image de novo. Ron Mowbrey says it is actually a normal film, pre-flashed. I was given a couple of rolls from the photo unit at work and was startled to see the edges of the film were black and the images positive. I thought I was getting microfilm. This kind of film used to be used to copy X-ray images but to keep the negative as a negative, which is what radiologists are used to.<br>

Now, could you have pre-exposed the frame accidentally? One always assumes there is an interlock frame winder and counter but some cameras can easily be over ridden and a pre-flashed positive result.<br>

Just a thought.</p>

[mfophotos]

<p>Read his follow-up comment. It was just a thin underexposed negative. </p>

[michel_pomerleau1]

<p>Hi everybody,</p>

<p>I would like to know what do you think. I had a similar situation, but just a part of the picture appears positive, even on the scans. There an obvious dichroic fog on the film, which might be related to the effect. The positive parts of the images are underexposed, since they are really thin. So it could match your explanation, but I don't get why it appears on the scans. The effect is visible from every possible angle.<br>

Here is an example (as a negative):<br>

http://www.michelpomerleau.com/Nonpublies/i-FdRsxng/A</p>

[lex_jenkins]

<p>Michel, that looks like it could be solarizing. But I've seen a few rare instances when extended development in certain developers - notably Rodinal - produced a similar effect. It seems more obvious with underexposed frames.</p>