Displaying blue photos on the forum

[Stustoys]

Would messing with the white balance help?
I mean something like setting the white balcance on a piese of "light red" paper?

(is this a rough way of doing what scottyd is talking about?)

I must say I've never even tried the different light type settings built into the camera. Time for some testing, great day for photos here.

Stuart

[nadroj]

Would a photo editor like the free GIMP be any good?

Jordan

[FenceFurniture]

Would messing with the white balance help?
I mean something like setting the white balcance on a piese of "light red" paper?

(is this a rough way of doing what scottyd is talking about?)

Not really Stuart - he's talking about manipulating the image after the event. Always best to start with the best data possible and then manipulate any adjustments required.

I must say I've never even tried the different light type settings built into the camera. Time for some testing, great day for photos here.

Stuart

Yep, there are some really useful settings in there. My shed has warm LED globes in it, along with a few halogen task lamps. For example, I always get a much better result using the Tungsten setting on the camera, rather the Auto White Balance (still stays a bit too warm).

[FenceFurniture]

Just had a thought re polarising which may yield the best result of all: a lens-polariser has absolutely no effect on metal whatsoever. However, double polarising does. This means that you polarise the light source with a PL gel (available from professional camera shops) and then use a P filter on the lens (either Linear or Circular, depending on what is recommended for your cameras light meter). It eliminates all reflections completely, including metal.

Link to supplier in the USA (but there will be some here).

Another USA link.

Have a look at page 12 of this (slow loading) pdf. It shows the effect of cross polarising on alum foil.

[simonl]

Hi all,

well my curiosity got the better of me. I dug out an old circular polariser and my digital camera, then cleaned the (flight ) rust of my square block from the hand scraping class and did a spot of spotting....

It was my intent to show a pic with and without the polariser in both sunlight and filtered light (in the shed). Unfortunately my results were completely unexpected. No difference! In fact I have not even bothered to post the pics because they look the same. Maybe a linear polariser may show better results, I dunno. I don't have a linear so I couldn't try it.

The only thing I can confirm (which everyone already knew anyway) is that you get better results with filtered sunlight or sunlight from overcast day than direct sunlight.

So, in short. Ignore my idea of a circular polariser!

Simon

[FenceFurniture]

...a lens-polariser has absolutely no effect on metal whatsoever. However, double polarising does.

To be expected Simon.

[scottyd]

Would messing with the white balance help?
I mean something like setting the white balcance on a piese of "light red" paper?

(is this a rough way of doing what scottyd is talking about?)

Yep, pretty much. Shooting raw gives you more range to play with in terms of correcting white balence. You could also do (in photoshop) an increase of contrast on the blue channel only, which would stop the rest of the picture from looking crap.

There are plenty of ways to manipulate the data in an image, but its only possible to manipulate data if you capture it first. If there isnt any blue light to be collected by the camera, then there will be no blue light in the image. If youre shooting in such a dark place (as someone else pointed out with the high iso comment), then you might not have the blues there to play with.

[Stustoys]

I have a light box with 6x30W tubes in it I could try. But that would be just about the worse light source for this sort of thing right? (or will this make things worse anyway?)

I had found that using max zoom helped*......though that would also increase the ISO right?

Lots of my scrapping is done at night(though DLS will help that for the minute) so while sun light might be nice, its not always possible. When I remember I like to take a picture each cycle with roughly the same setup, as it lets me flip through them to see how things are coming along. I doubt its really necessary for the pros.

Stuart

*didnt know why but I think its covered in the above pdf.

[Michael G]

Not really Stuart - he's talking about manipulating the image after the event. Always best to start with the best data possible and then manipulate any adjustments required.

Don't know where you got that idea from - in the first post I asked about filters. I don't want to get into lots of post picture manipulation. Whether by changing a camera setting or using some sort of filter, I just want a picture that can be displayed that will show spotting clearly, especially for finish work (that is, thin layers of blue).

Michael

[FenceFurniture]

I have a light box with 6x30W tubes in it I could try. But that would be just about the worse light source for this sort of thing right? (or will this make things worse anyway?)

Sodium vapour would be worse......

I had found that using max zoom helped*......though that would also increase the ISO right?

The ISO shouldn't change just by zooming (unless there's some fancy built in algorithm to increase ISO with zooming to assist with camera shake - never heard of it though).

Lots of my scrapping is done at night(though DLS will help that for the minute) so while sun light might be nice, its not always possible. When I remember I like to take a picture each cycle with roughly the same setup, as it lets me flip through them to see how things are coming along.

That adds a new twist which can really only be solved by repeatable artificial light. Tungsten or LED will give the biggest part of the spectrum

[FenceFurniture]

Don't know where you got that idea from - in the first post I asked about filters. I don't want to get into lots of post picture manipulation. Whether by changing a camera setting or using some sort of filter, I just want a picture that can be displayed that will show spotting clearly, especially for finish work (that is, thin layers of blue).

Michael

Apologies Michael, I was referring to nadroj's post - I should have been clearer. Agreed that post pic fooling around is to be avoided as much as possible. Just wish I still had a PL gel for a light to experiment with.

[cba_melbourne]

There are two issues to consider:

1)

Light in real life contains the whole spectrum of colors, ranging seamlessly from violet at one end to red at the other end, with blue green yellow and orange in between.

Photography is only a simplification of this reality. Photography only uses three colors (red, green and blue). By mixing these it tries to reproduce reality as good as possible. For example, photography can not faithfully reproduce a color like gold or silver. The former will look as a dull yellow, the latter as a dull grey.

This is the reason, why in printing often more than only three colors are used. If you look at shiny cardbord packaging boxes, you will often find an area under a lid where a strip of reference colors is printed. Besides the standard colors yellow, magenta, cyan and black you may see one or several additional colors are used, depending of the items shown in the picture. The use of a separate color "gold" or "silver" can be used to print realistic looking goldcoins or a silver trophy. The simplification of only using only a limited number of colors also has another effect. For example, two pieces of colored tissue may look exactly the same under daylight, buy may appear to be quite different colors under incandescent light. Something important to consider in the tinting business.

Back to the machine way scraping pic. If you wanted to represent this in an expensive color print book, you would add to the standard colors the special colors for steel and for "prussian blue" (which is the name of the blue color dye used in layout blue). But in photography you cannot add to the three colors RGB. You are stuck with the three color RGB and whatever can be mixed with these three colors.

2)

In a photography, you record the colors and intensities of light reflected from the surfaces of the objects in the picture. Sunlight contains equally all colors in the spectrum (a continuous spectrum), so does the light from halogen bulbs. But if you look at the light from fluorescent bulbs, it only contains a few very narrow lines at certain wavelengths, NOT a continuous spectrum. If almost no blue is present in such light, then you should not expect to see much blue reflected either. In an extreme case, where blue light is completely missing, blue surfaces will be shown as grey. An extreme example are the yellow Natrium vapor street lights, they emit almost monochromatic light. If you have such a yellow street lamp, do this experiment at night: take your kids box of color pencils under this street light, how many colors can you identify? The yellow pencil will look very bright yellow, all others will only appear as different shades of grey. You are effectlively color blind. Hence the rule: if you need to see proper colors, you should never use fluorescent or LED light. Choose Sunlight, or at least some bright form of incandescent light instead.

You can enhance the "blues" in your picture in several ways. You can use a lamp with a "higher color temperature". For example, a halogen bulb emits more blue color if operated at a higher voltage. The higher voltage results in a hotter filament, hence also the term higher color temperature. But there are bulbs that are made with a finer filament, to achieve the same effect at normal voltage. In general, lamps with a higher color temperature have a shorter life too. You could also put a blue filter in front of the lamps and achieve the same outcome. The blue filter lets blue pass but absorbs yellow.
Or you can manipulate the picture after it being taken, using a photo editing software that lets you apply a blue filter. Chris

[Oldneweng]

I have a light box with 6x30W tubes in it I could try. But that would be just about the worse light source for this sort of thing right? (or will this make things worse anyway?)

I had found that using max zoom helped*......though that would also increase the ISO right?

Lots of my scrapping is done at night(though DLS will help that for the minute) so while sun light might be nice, its not always possible. When I remember I like to take a picture each cycle with roughly the same setup, as it lets me flip through them to see how things are coming along. I doubt its really necessary for the pros.

Stuart

*didnt know why but I think its covered in the above pdf.

Most people tend to do most of their scrapping at night. I think it may have something to do with the consumption of alchohol that also happens more at night.

Dean

[Stustoys]

Its muscle relaxant Dean


I believe photograhers used to run 240V bulbs at about double V. Sure they wouldnt last long but it was no big deal.
Anyone got an idea how far over volt you can run say a car 12V headlight?
Would they be better on AC or DC?
(I guess I could try a headlight as is first)

Stuart

[Michael G]

I went out and had a play with the camera settings, both white balance and "scenes" while taking photos without flash. One thing that is noticable is the unevenness of the lighting I have. On the right side of the photo the light is coming from a skylight. The fresh scraping adds an extra degree of difficulty picking up the blue. As a few have suggested, a diffuser is needed to give even light. None of them had a particularly noticeable affect in making the spotting stand out. The best was the "food" setting (below). The subject is a little 4"x10" Wing surface plate , ex DoD. I've circled a couple of places where some kind soul has used it as an anvil. For some reason it is crowned in the middle when I blue it against the cheeseboard (spring back after being thumped?). Why would you use a beautifully scraped surface like that?

P1010927a (Medium).JPG

The other photo (below) is the same thing but manipulated in MS Office Picture Manager where I've turned both the amount and the hue right down in the colour settings. This is the sort of effect that I was hoping to get straight from the camera - the back ground is muted but the blue is bright. If I can find the instructions that came with the camera I may be able to define a custom setting that does that although it is a long shot.

P1010927b (Medium).JPG

I guess the only way I'll get real time is with a set of those google glasses, a web cam and some costly software. At least for posting photos here there looks to be a way of bringing up the contrast.
This the photo of Richard's using the same treatment. Is it any better? Hard to say.
RC2.jpg

Michael