CLPEX Chat Board

Anyone have a tried and true method for capturing latents on LCD screens? Our CSIs are turning in images of latent prints processed with powder and the RGB pixels/noise that is part of the screen are making clarification difficult. Anything I can pass on?

I haven't had to do it in a while so I don't have any good suggestions for them at this point.

Lift?

LIFT??? Surely you can't be serious! That is unscientific 20th century nonsense. This is the 21st century, ruled by academicians and theoretical scientists. Digital photography is the 21st century method. Get real. You must abandon archaic, obsolete, anachronistic methodologies if you want to join the 21st century of latent-print examination.

Polarizing filter? I'm a little confused. Are they photographing developed latents with the LCD screen on? I'm kind of having a hard time understanding what type of LCD screen would be difficult to photograph a latent on.

The attached photo illustrates what I'm seeing. There are those pixels in the background (they're not called pixels, not sure what they are actually called) that are creating all sorts of background interference. A pattern removal filter would be great but I don't have one of those.

It's also similar to trying to photograph prints on a rearview mirror; there's that double 'ghost' image behind it giving the appearance of a blurry print. Lifting was completed but they were extremely faint on the card.

I'm still able to render a conclusion based on this photo but was hoping to generate a few tips on how to reduce that background interference.

Aside from an FFT filter, you could convert this into CMYK and isolate the yellow channel or even the magenta. An LCD screen consists of two layers of polarized glass with the liquid crystal sandwiched between them, which is why you get the "ghosting" effect.

Dr. Borracho, I am glad to see you are finally on board the 21st century train sir. Tickets please!

NRivera wrote: ↑Wed Jul 03, 2019 9:18 amDr. Borracho, I am glad to see you are finally on board the 21st century train sir. Tickets please!

For a dozen years, a good 12 year old single malt would transport me back to my century. Then it took a rather expensive 18 year old scotch to do the trick. Now we're up to the 21 year olds they keep under lock and key. Do you have any idea how much a shot trip back to the Twentieth Century costs today? In a few more years, that trip will cost the price of a new car! What's an old borracho to do???

In all seriousness. Just lift it. If you need a digital photo for your workflow, then photo the lift.

You could also try Axial lighting:

AXIAL LIGHTING
A clear piece of glass is placed between the subject and lens at a 45° angle. The light source is positioned parallel to the film place and 45° to the glass. While the light is transmitted through the glass, some is reflected downward directly on the subject. This technique is effective when photographing fingerprints on mirrors and into glasses or cups.

Without a lot of time to really play with it, I converted to CMYK, isolated the yellow channel, inverted it, then applied to the original and this is the best I could come up with.

I'm a bit rusty on my photoshop as I have been spoiled with the DCS-5. The FFT filter would make quick work of that pattern. Peter's suggestion of axial lighting is great, in the end that's what this boils down to: a lighting issue.

ER wrote: ↑Wed Jul 03, 2019 9:49 am In all seriousness. Just lift it. If you need a digital photo for your workflow, then photo the lift.

I would have posted a scan of the lift card but it was so faint, I didn't even choose to do that. Attempts to darken it would have resulted in equal darkening of the background and I would be in the same boat as the image, albeit just the opposite grayscale values.

josher89 wrote: ↑Wed Jul 03, 2019 12:01 pmI would have posted a scan of the lift card but it was so faint, I didn't even choose to do that.

Sometimes, doing a levels adjustment in the scan box prior to scanning gives you much better results than processing the image after scanning. Did you try that?