RPX 25 + red filter == way too much contrast

**bobbotron** · 04-12-2018, 07:19 AM - **1 Like**

I did some shots with RPX 25 using a red filter last week. Shot at EI 25, dev'd in rodinal 1+50 for 11 minutes. I printed a photo from it last night, and the contrast was over the top, it looked like a bad photoshop job. This film likes to blow out highlights really hard, the red filter really ramped it up. Live and learn, the shots I did without the filter came out much better/manageable.

**bobbotron** · 04-12-2018, 12:13 PM

This thread is a bit weak without photos. I don't have a scanner, but you can get the idea.

photoptimist · 04-12-2018, 01:38 PM

Interesting and good to know.

(Does that imply that a cyan filter might lower the contrast???)

**bobbotron** · 04-12-2018, 03:05 PM

Yeah, I ran out of time to try varying contrast filtration, but I'll probably try next enlarging session. This is interesting, I expected this photo to come out totally different than it did. This photo doesn't really do it justice, poor light today. The white sections of the image are crystal clear white.

tuco · 04-14-2018, 06:58 AM

I tried RPX 25 in Rodinal 1+50 per the box develop time too and it was a little over cooked but scannable. One thing about Rodinal is how you agitate it really can speed up/down the film like no other developer it seems. The film also feels like a long toe film too. But I need to take more pictures with it.

maw · 04-16-2018, 05:04 PM

Originally posted by bobbotron

I did some shots with RPX 25 using a red filter last week. Shot at EI 25, dev'd in rodinal 1+50 for 11 minutes. I printed a photo from it last night, and the contrast was over the top, it looked like a bad photoshop job. This film likes to blow out highlights really hard, the red filter really ramped it up. Live and learn, the shots I did without the filter came out much better/manageable.

Hi bobbotron,

I stopped developing films some years ago, but I remember the Rodinal, is a disposable development, fine-grained and very contrasting, The red filter alone

and more if paired with a polarizer darkens the blues (sky) making it almost black. What should be considered is that it can cause underexposure when combined with a TTL reflex with CdS cells.

So you feel passionate, a link ROLLEI RPX 25 ISO: well returned low iso ( it is in Italian, you can translate it).

tuco · 04-17-2018, 10:26 AM

A red filter cuts out the blue light. Shadows have blue light in them. So if not adjusted for you can get dark shadows with a red filter. And if a film exhibits a long-toe characteristic, then you can get really deep shadows.

**gofour3** · 04-26-2018, 07:30 AM

Originally posted by tuco

A red filter cuts out the blue light. Shadows have blue light in them. So if not adjusted for you can get dark shadows with a red filter. And if a film exhibits a long-toe characteristic, then you can get really deep shadows.

I shot a few test Fomapan R100 slides once with a red & polarizer filter. The results looked like a 1930's horror movie, interesting experiment but not for everyday use........

Phil.

**twilhelm** · 05-04-2018, 06:54 AM

Rodinal has always been my favorite developer. I learned early on to be very careful with agitation. It’s always better to agitate less than more. I recently developed a roll of Fomapan 100 and wasn’t paying attention and ended up agitating the film a couple of extra times. It came out extremely high contrast with all highlights blown out.
I haven’t tried the RPX film, but it’s on my short list.

**Digitalis** · 05-22-2018, 08:47 PM

Originally posted by bobbotron

Shot at EI 25, dev'd in rodinal 1+50

What was your frequency of agitation? You might want to try 1+100 that should knock the contrast back a stop or two.

Originally posted by bobbotron

This film likes to blow out highlights really hard, the red filter really ramped it up

I tried to find spectral sensitivity curves on this film but I can't seem to find anything from a reputable source - It may well have heightened red sensitivity and might benefit from having exposure pulled back 1/2 a stop when shooting with a red filter.

Originally posted by twilhelm

Rodinal has always been my favorite developer. I learned early on to be very careful with agitation.

Agitation has pronounced effect on highlights, and it doesn't help that Rodinal is particularly aggressive in these areas*. Which is why I switched to pyro staining developers as their staining characteristic tempers aggressive development that can occur with increased agitation. The main two drawbacks of Pyro Vs Rodinal is Pyro is toxic and the developing solution requires very pure constituents and even then it has a short shelf life.

* stock to mid dilutions, at high dilutions it is more subdued. With larger formats [6X6 and up] Rodinal it is prone to getting exhausted so increased agitation or lower dilution is needed.

**fs999** · 05-24-2018, 07:35 AM

Originally posted by Digitalis

I tried to find spectral sensitivity curves on this film but I can't seem to find anything from a reputable source - It may well have heightened red sensitivity and might benefit from having exposure pulled back 1/2 a stop when shooting with a red filter.

I have only found a German PDF on www.maco-photo.de : Rollei_RPX_25_dt.pdf

**Digitalis** · 05-24-2018, 08:00 AM

Originally posted by fs999

I have only found a German PDF on

Das ist sehr gut!

The film doesn't seem to have too much red sensitivity - from the look of the curves compared to a pretty standard film like T-max 100 sensitivity extends further into the IR range than RPX 25. The recommended filter factor for a no.25 red filter in the publication for RPX 25 is 2.25 stops, for Kodak T-max 100 the no.25 red filter calls for 3 stops correction.

tuco · 05-24-2018, 09:15 AM

Originally posted by Digitalis

Das ist sehr gut!
...
The recommended filter factor for a no.25 red filter in the publication for RPX 25 is 2.25 stops...

Geesh, someone comes up with that number. How do you set your camera to a 1/4 stop? Why not just round to a 1/3 stop. And in the case of my manual cameras a 1/2 stop is the best they can do.

**Digitalis** · 05-24-2018, 09:23 AM

2.25 stops is what one should expect of Teutonic precision. 1/2 stop should be close enough, negative films handle overexposure better than digital can.

tuco · 05-24-2018, 09:29 AM

Originally posted by Digitalis

2.25 stops is what one should expect of Teutonic precision.

It makes no sense. Just say 2 stops. Close enough and a tangible number too.

All my exposures (with/without filters) are rounded to the nearest stop. And with all the variables from developing film to making the final print/scan seems to not make any difference.

04-12-2018, 07:19 AM - 1 Like	#1
bobbotron Site Supporter Join Date: Jan 2015 Location: Ottawa, ON Photos: Gallery Posts: 3,349	RPX 25 + red filter == way too much contrast I did some shots with RPX 25 using a red filter last week. Shot at EI 25, dev'd in rodinal 1+50 for 11 minutes. I printed a photo from it last night, and the contrast was over the top, it looked like a bad photoshop job. This film likes to blow out highlights really hard, the red filter really ramped it up. Live and learn, the shots I did without the filter came out much better/manageable.

04-14-2018, 06:58 AM	#5
tuco Pentaxian Join Date: Jul 2009 Location: Pugetopolis Posts: 11,025	I tried RPX 25 in Rodinal 1+50 per the box develop time too and it was a little over cooked but scannable. One thing about Rodinal is how you agitate it really can speed up/down the film like no other developer it seems. The film also feels like a long toe film too. But I need to take more pictures with it. Last edited by tuco; 04-14-2018 at 07:06 AM.

05-22-2018, 08:47 PM	#10
Digitalis Site Supporter Join Date: Mar 2009 Location: Melbourne, Victoria Photos: Gallery Posts: 11,694	Originally posted by bobbotron Shot at EI 25, dev'd in rodinal 1+50 What was your frequency of agitation? You might want to try 1+100 that should knock the contrast back a stop or two. Originally posted by bobbotron This film likes to blow out highlights really hard, the red filter really ramped it up I tried to find spectral sensitivity curves on this film but I can't seem to find anything from a reputable source - It may well have heightened red sensitivity and might benefit from having exposure pulled back 1/2 a stop when shooting with a red filter. Originally posted by twilhelm Rodinal has always been my favorite developer. I learned early on to be very careful with agitation. Agitation has pronounced effect on highlights, and it doesn't help that Rodinal is particularly aggressive in these areas. Which is why I switched to pyro staining developers as their staining characteristic tempers aggressive development that can occur with increased agitation. The main two drawbacks of Pyro Vs Rodinal is Pyro is toxic and the developing solution requires very pure constituents and even then it has a short shelf life. stock to mid dilutions, at high dilutions it is more subdued. With larger formats [6X6 and up] Rodinal it is prone to getting exhausted so increased agitation or lower dilution is needed. Last edited by Digitalis; 05-22-2018 at 08:56 PM.

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04-12-2018, 01:38 PM	#3
photoptimist Pentaxian Join Date: Jul 2016 Photos: Albums Posts: 5,122	Interesting and good to know. (Does that imply that a cyan filter might lower the contrast???)

04-12-2018, 03:05 PM	#4
bobbotron Site Supporter Join Date: Jan 2015 Location: Ottawa, ON Photos: Gallery Posts: 3,349 Original Poster	Yeah, I ran out of time to try varying contrast filtration, but I'll probably try next enlarging session. This is interesting, I expected this photo to come out totally different than it did. This photo doesn't really do it justice, poor light today. The white sections of the image are crystal clear white.

04-16-2018, 05:04 PM	#6
maw Pentaxian Join Date: Feb 2014 Location: Sassari (Italy) Posts: 1,118	Originally posted by bobbotron I did some shots with RPX 25 using a red filter last week. Shot at EI 25, dev'd in rodinal 1+50 for 11 minutes. I printed a photo from it last night, and the contrast was over the top, it looked like a bad photoshop job. This film likes to blow out highlights really hard, the red filter really ramped it up. Live and learn, the shots I did without the filter came out much better/manageable. Hi bobbotron, I stopped developing films some years ago, but I remember the Rodinal, is a disposable development, fine-grained and very contrasting, The red filter alone and more if paired with a polarizer darkens the blues (sky) making it almost black. What should be considered is that it can cause underexposure when combined with a TTL reflex with CdS cells. So you feel passionate, a link ROLLEI RPX 25 ISO: well returned low iso ( it is in Italian, you can translate it).

04-17-2018, 10:26 AM	#7
tuco Pentaxian Join Date: Jul 2009 Location: Pugetopolis Posts: 11,025	A red filter cuts out the blue light. Shadows have blue light in them. So if not adjusted for you can get dark shadows with a red filter. And if a film exhibits a long-toe characteristic, then you can get really deep shadows.

04-26-2018, 07:30 AM	#8
gofour3 Site Supporter Join Date: Oct 2008 Location: Vancouver, Canada Posts: 8,090	Originally posted by tuco A red filter cuts out the blue light. Shadows have blue light in them. So if not adjusted for you can get dark shadows with a red filter. And if a film exhibits a long-toe characteristic, then you can get really deep shadows. I shot a few test Fomapan R100 slides once with a red & polarizer filter. The results looked like a 1930's horror movie, interesting experiment but not for everyday use........ Phil.

05-04-2018, 06:54 AM	#9
twilhelm Loyal Site Supporter Join Date: Feb 2009 Location: Florida Photos: Gallery \| Albums Posts: 2,369	Rodinal has always been my favorite developer. I learned early on to be very careful with agitation. It’s always better to agitate less than more. I recently developed a roll of Fomapan 100 and wasn’t paying attention and ended up agitating the film a couple of extra times. It came out extremely high contrast with all highlights blown out. I haven’t tried the RPX film, but it’s on my short list.

05-24-2018, 07:35 AM	#11
fs999 Loyal Site Supporter Join Date: Jul 2008 Location: Luxembourg Photos: Gallery Posts: 8,636	Originally posted by Digitalis I tried to find spectral sensitivity curves on this film but I can't seem to find anything from a reputable source - It may well have heightened red sensitivity and might benefit from having exposure pulled back 1/2 a stop when shooting with a red filter. I have only found a German PDF on www.maco-photo.de : Rollei_RPX_25_dt.pdf

05-24-2018, 08:00 AM	#12
Digitalis Site Supporter Join Date: Mar 2009 Location: Melbourne, Victoria Photos: Gallery Posts: 11,694	Originally posted by fs999 I have only found a German PDF on Das ist sehr gut! The film doesn't seem to have too much red sensitivity - from the look of the curves compared to a pretty standard film like T-max 100 sensitivity extends further into the IR range than RPX 25. The recommended filter factor for a no.25 red filter in the publication for RPX 25 is 2.25 stops, for Kodak T-max 100 the no.25 red filter calls for 3 stops correction.

05-24-2018, 09:15 AM	#13
tuco Pentaxian Join Date: Jul 2009 Location: Pugetopolis Posts: 11,025	Originally posted by Digitalis Das ist sehr gut! ... The recommended filter factor for a no.25 red filter in the publication for RPX 25 is 2.25 stops... Geesh, someone comes up with that number. How do you set your camera to a 1/4 stop? Why not just round to a 1/3 stop. And in the case of my manual cameras a 1/2 stop is the best they can do.

05-24-2018, 09:23 AM	#14
Digitalis Site Supporter Join Date: Mar 2009 Location: Melbourne, Victoria Photos: Gallery Posts: 11,694	2.25 stops is what one should expect of Teutonic precision. 1/2 stop should be close enough, negative films handle overexposure better than digital can.

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05-24-2018, 09:29 AM	#15
tuco Pentaxian Join Date: Jul 2009 Location: Pugetopolis Posts: 11,025	Originally posted by Digitalis 2.25 stops is what one should expect of Teutonic precision. It makes no sense. Just say 2 stops. Close enough and a tangible number too. All my exposures (with/without filters) are rounded to the nearest stop. And with all the variables from developing film to making the final print/scan seems to not make any difference.