What light to evaluate prints

[nrdlnd]

I know there has been a thread about this before but it ended in January. How many here on the forum evaluate their prints in a standardized environment like the D50? Roger B. uses the Solux bulbs that's supposed to be very good and they seem to be the 'de facto standard' among artists. There is an ISO-standard for this: ISO 3664:2009. I think the Solux halogen bulbs follow this standard (I can't see though on there website that they claim to follow it) but there are also other 'bulbs' that claim to follow the standard for example the Osram Color Proof fluorescent tubes. I think they are used a lot in the graphic industry. There seems to be some kind of agreement on the net that it's not possible to use fluorescent tubes for critical evaluatment because of some pronounced bands in the spectrum.

My question is if someone has actually USED these fluorescent tubes? Has anyone compared them to the Solux bulbs? They have some advantages compared to the Solux halogen bulbs. They are much more power efficient. They give a more diffused light. They are possible to dim (with the correct electronic reactor) without changing the qualiy of the light (the Solux lamps change color temperature if you dim them). The tubes has a much longer life compared to the halogen bulbs. The halogen bulbs become very warm and may be a fire hazard if you leave them unattended. Is it possible to see the spikes in the spectrum when you evaluate colors from the ISO tubes?

I would like to try this out with an 4x18W armature and replace the ballast to a dimmable electronic HF-ballast. With an electronic HF-ballast you get a longer life of the tubes and maybe even more if you dim them. Is this a silly beforehand doomed idea? Has anyone own experiences using these ISO-certified lights for print evaluation?

Regards,

Per

 

[nrdlnd]

Follow up:

I have ordered a 4x18w armature from here in Sweden. This armature has a rather even output with about 60 degrees angle. There are cheaper alternatives to find on eBay but I don't know how even the output are from them. The armature already has an HFE ballast but I need to be able to dim the lamp so I have ordered a dimmable one on eBay for replacement. I have also ordered 4x18w Osram Color Proof fluorescent tubes. I still have to find a standard 0-10V dimmer at a good price.

To be able to make a comparison with the Solux lamps I have ordered two 4700K 35w halogen bulbs with black back and diffusing glass/filter from Solux in the US (the 5000K bulbs were out of stock). This company won't sell outside US and Canada of some obscure reason so they will send it to my sister in the US and she will send it to me in Sweden. I have ordered adapters from E14 to MR16 that will fit in cheap armatures from IKEA. I do also have to buy a 12V transformer and that's not difficult to find.

The cost will be about 50% higher for the ISO fluorescent variant but I have only ordered two Solux lamps but if I wanted them as a permanent solution I should have ordered at least four because of the lower lifetime.

This will be an interesting comparison but only a subjective evaluation. I will compare under these two illuminants but also natural daylight. I don't have the necesssaray measurement instruments. I just got an idea that this equipment may be possible to use with "Illumread" in Argyllcms and my i1Pro to be able to profile OBA-papers!? I think it's good to have a consistent and standardized light source for that. Besides I will only profile the RC-papers I have left as I will not buy more of these papers. I have nothing against the protective PE-layer but I hope someone will manufacture a RC-paper with baryta as the reflective layer instead of the optical brighteners from DOW Chemical. OBA:s has absolutely nothing to do in photographic papers as the colors vary depending on the UV-content of the illuminant.

Edit: The dimmer may be overkill. To get the recommended 2000 Lux with the Color Proof fluorescent lights the distance from the light source and the paper you want to proof must be rather short. I estimate it to 50cm or maybe even less. To be able to regulate the light can be valuable anyway if you want to see how the picture looks under lower light conditions but you can also look at it a longer distance from the light source. It could also be valuable if you want to correlate it with the intensity from the display. I just wonder if the light intensity from the Solux lamps will be enough? I will buy a cheap luxmeter or use an app on the mobile.

Regards,
Per

 

[nrdlnd]

I've just got the armature for the fluorescent tubes. The Osram Color Proof tubes are only available as T8 tubes and it was more difficult than I thought to find a suitable armature. T8 is rather old technology. I bought a cieling mount 4x18W armature from ELG-Leuchten in Germany. They have an eBay shop. I bought the one with BAP-Raster without fluorescent tubes. It's possible to find under "Raster Leuchte". It has parabolic reflectors of aluminium for greater effiency and an electronic reactor that's not dimmable. I think it may be possible to order a variant with a dimmable reactor. The parabolic reflectors raises the effiency but I havent measured with how much. The reflector directs the light and I think that's good. The illumination seems to be rather even.

The Color Proof tubes I did buy here in Sweden as there are transport restrictions. They were rather expensive. I have just put the tubes in the armature and made a provisoric connection to the mains and measured the output. The tubes are not burned in yet. I've measured with a luxmeter and get 2000 Lux about 75 cm from the fluorescent tubes so it's not absolutely necessary to dim the light if you keep this distance from the light when evaluating pictures. I will probably have a shorter distance in my "light box" so I will change the reactor to a dimmable variant. There exists similar armatures with 3x18W tubes that may give a sufficient bright light or it's possible to use an armature with a less directional light.

I will just say that don't make changes to an armature like this If you don't know what you are doing. Even if it's some years ago I've been working professionally as an electrician. That means that I have a great respect for what comes out of these two (or three) holes in the wall!

Per

 

[The Hat]

Trying to use a dimmer on a standard florescent unit and tube is not very practical solution and would work out mighty expensive if it worked, a much better method in my opinion would be to use a simple set of diffusers to get the required illumination from the unit..

 

[nrdlnd]

Trying to use a dimmer on a standard florescent unit and tube is not very practical solution and would work out mighty expensive if it worked, a much better method in my opinion would be to use a simple set of diffusers to get the required illumination from the unit..

A very good proposal!

That's a good solution if you don't know what to do or don't have anyone with the knowledge that can help you. If you can get the armature with a dimmable electronic reactor then you have to buy a dimmer (a special potentiometer for the 0-10V that comes from the reactor). The one I've bought is Jung 240-10. It will cost 30-40 €. I've also found a dimmable reactor on eBay for about the same. Total about 100 €. For this you get a dimmable light that doesn't change in color temperature. With a luxmeter you can regulate it to the correct illumination. Probably longer life of the fluorescent tubes and you save some on the electric bill. I do also want to keep the rather directional light from the fixture not to get too much reflections from the surroundings.

Edit: You can buy a luxmeter and it's possible to find one for about 30€. There are also free apps to download to your mobile. I've tried one from AFS-software. Because of different hardware on phones you have to calibrate it against a "real" luxmeter. It's necessary to check the calibration under different light levels but then you have a luxmeter for "free" .

Per

 

[nrdlnd]

The D-50 ISO 3664:2009 illuminant is the most recent standard for the viewing light in the graphic industries. Light intensity should be about 2000 Lux. Compared to the older standard from 2000 there are more UV-content. When I'm comparing the same picture printed on papers with different OBA-content with the Osram Color Proof tubes (they are supposed to follow the latest ISO-standard) there is a great difference between an RC-paper with a lot of OBA. It's much whiter (bluish white) compared to papers with less or without OBA. It may or may not look ok under a light with less UV-content. When I have been able to install the Solux lamps I will make the same comparison and see if they emit enough UV-light to invoke the OBA:s. This may be good or bad depending under what viewing conditions you want to view your pictures. An alternative to the Osram Color Proof are the Philips Graphica tubes. They are often available for less money than the Osram variant but they do not claim to follow the latest ISO-standard. I'm not going to purchase these to make a comparison.
Per

 

[nrdlnd]

My "light box" will be in a separate part of the room where there has been a sink before. I have to paint the walls and also the table with "neutral gray" not to get coloured reflections. Does anyone have an experience of what colour to use? I have seen recommendations to go to the paint store and ask them to mix "ncs 3000". Anyone?
Per

 

[The Hat]

That’s a good idea to paint the walls grey simply because you won’t get any feed back from your soundings (Interference, or reflection)

I’d choose the 421 Grey rather than the 00 A 05 Grey because it’s more neutral..

 

[Mags]

use Flourescent lights with a temp of 5000 - 5000K high CRI at or above 90 ideally these are called full spectrum lights, CRI of 100 is perfect but this isnt available, these will give a smooth spectrum lower the cri the more spikes in the spectrum meaning some colours render differently depending on wavelength. Walls neutral in colour ideally no windows and dont wear that Hawaiian shirt you love so much.

OH and a GOOD monitor like an EIZO or a Spectraview REF.

 

[nrdlnd]

I’d choose the 421 Grey rather than the 00 A 05 Grey because it’s more neutral.

Thanks for the proposal! I don´t understand though why this colour is more neutral than NCS 3000?

use Flourescent lights with a temp of 5000 - 5000K high CRI at or above 90 ideally these are called full spectrum lights,

Yes and I'm comparing the Solux halogen lamps with the Osram Color Proof fluorescent tubes.

I've just got adapters to the Solux lamps and compared them (two lamps 4700K with black back fed with 12V) to the Osram tubes. I ordered the plane diffusers but they did send the convex ones and I think that was good as they diffuse the light better. Without diffusers I think the lamps are unusable! The light intensity is very uneven and the light spectrum of the light is uneven (without diffuser)! With diffusers it still covers a rather small circle and I think it's necessary with four lamps to be able to cover enough area. They become hot and I wouldn't leave them unattended! The quality of the light is good but they seem to have less blue/UV-content compared to the fluorescent tubes. It's easier to see the bad effect of OBA:s with the fluorescent tubes.

The quality of the light is also good from the fluorescent tubes but the light spread is much better and also the light output. It's too early to make a conclusion what lamps to prefer that needs more comparisons. What surprise me is that the fluorescent tubes hold up so well against the Solux lamps and even surpass them in many aspects.

I will come back later when I have more experience.

Per