Archive for November, 2009

Photoshop Feature Requests

Nov 24th, 2009 - Filed under: Blog, Photoshop

When I present workshops, many people frequently ask for a handful of features. Two of the most popular are improvements to the History Log and getting back the LayerComps to PDF script. Two questions that are raised when these issues are brought up include, “Why is it this way?” and, “How do we let Adobe know we want this or that feature?”

The main reason why features don’t exist that you may think are obvious needs, is that Adobe doesn’t know that it’s a needed feature. If 100 people ask for a feature, then that gets their attention, but if only one person asks, it simply won’t carry the same weight of the frequently requested features.

I suggest that if there are features that you want, that you let Adobe know. You can do this by posting to the Adobe Photoshop Feature Request Forum. You’ll have to register to post, but it’s relatively painless.

What about finding solutions to problems you are having? Again, Adobe can’t fix a problem without knowing that it exists. They have a Photoshop Macintosh Forum, and a Photoshop Windows Forum.

Use these forums to let Adobe know what you’d like, what’s working and what’s not working. Another great resource is John Nack’s Blog. John is the Principal Product Manager for Photoshop at Adobe. He frequently asks readers of his blog for feedback on features. Keep an eye on his blog, and provide him with feedback when he asks for it in addition to posting on the forums listed above. If we don’t let Adobe know what we want, then we can only blame ourselves if we don’t get those features.

Reverse Projection Photogrammetry

Nov 22nd, 2009 - Filed under: Blog, Image Analysis, Photography, Video Analysis

The Law Enforcement and Emergency Services Video Association (LEVA) held it’s annual conference this week. I was fortunate to attend the two day pre-conference workshop on reverse projection photogrammetry presented by Richard Vorder Bruegge, Walter Bruehs, and Chris Iber, all from the FBI Forensic Audio, Video, and Imaging Analysis Unit.

Reverse Projection Photogrammetry is used to measure objects in a photograph or video. It can be used to determine if an individual could be excluded or included as a suspect based on height. In addition to using this method to determine the height of an individual in an image, I have used this technique to determine the position of objects in relation to their surroundings (after the objects were removed), the distance of safety barriers in construction scenes (after the construction was completed and the barriers removed), the size of cracks in a sidewalk (after the sidewalk was repaired), etc. from photos of those scenes.

The workshop covered issues related to the methodology and foundations of this technique. Any forensic image analyst or forensic video analyst who hasn’t yet had the opportunity to take this workshop should do so. It has been offered at the LEVA conference for two or three years, and also at the IAI Annual Conference.

Using Photoshop and Bridge for On-Screen Comparisons

Nov 9th, 2009 - Filed under: Blog, Fingerprints, Image Analysis, Photoshop, Video Analysis

Someone recently posted a question on the CLPEX website regarding on-screen comparisons. This question was specifically about fingerprint comparisons, but the method is the same whether comparing prints, footwear, vehicles, etc.

The first step is to determine which images to use (or eliminate). I frequently use Adobe Bridge for this. I set up Bridge in the Filmstrip workspace. If I need to compare two or three images to decide which I will use for the final comparison, I select multiple images and use the loupe tool to compare details. The loupe tool provides a 100, 200, 400, or 800 percent magnification of a portion of each image in the Preview panel. Just click on an image in this panel to activate the loupe, click and drag it to move it, click it again to close it. You can display one loupe on each image in the Preview panel, as shown here:

This image shows two images in Bridge with the loupe tool.

This image shows two images in Bridge with the loupe tool.

Once the images are selected, they can be opened into Photoshop for comparison.

If the images are of the same resolution and approximately the same cropping, then they can be synchronized for zooming and scrolling. Do this by choosing the “Zoom all Windows” and “Scroll all Windows” in the options for the Zoom and Hand tools. Now, if you tile the images side-by-side, and zoom, both images will zoom; scroll one, and the other will scroll as well.

A new blank layer can be added to each image and marks can be made on that blank layer to indicate various features. Multiple layers can be used to better separate different categories of features, etc. With the Extended version of Photoshop CS3 or CS4, the Count tool can be used to mark features.

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So, What’s the Story on Resolution?

Nov 5th, 2009 - Filed under: Photography

My post on Synchronizing Video has generated a few comments related to image resolution. Three people, all of whom have a significant background in forensic imaging, have made rather divergent comments. Multiple topics are being addressed, from crime scene, accident and evidence photography to latent print photography to SWGFAST guidelines/requirements to the resolution of video security camera systems.

In all of these, there is a common element regarding resolution – the image should have the resolution to see the details for the purpose of the analysis. In a crime scene, this may be enough resolution to see the relationship of different objects in the image to each other. In a fingerprint, this may be second or third level detail. In the security camera it may be enough to read a license plate or see individualizing features in an object or person.

In security video, I almost always wish there was more detail, or higher resolution. These images are frequently 640 X 480 pixels or less. In addition, they are often highly compressed, the camera is at a bad angle, the lighting is poor, the optics are poor quality and dirty, and the subject of interest is frequently in the distance. Very few in the forensic video analysis field would argue that we’d all prefer security video with more resolution.

In fingerprints, I have seen some pretty good prints at resolutions as low as 300 PPI. The SWGFAST guidelines currently call for a minimum 1,000 PPI at a native resolution. So, can a fingerprint examiner use images that are less than 1,000 PPI or that may have been scanned with a scanner that interpolates when set to 1000 PPI? Of course they can – and they do.

Regarding crime scene, accident and evidence photography, many people compare digital imaging to film and suggest only using digital cameras that match the resolution of film. When I ask these proponents which film format (disc, 110, APS, 35mm, 6 X 6, 4 X 5), which film brand, which ISO, using which optics, whether they are concerned with tonal resolution as well as optical resolution, etc., they usually are unable to answer. There is nothing special about film that makes it a standard for measuring resolution.

When taking photographs, we simply need to know what level of detail is required, then be certain that we capture that level of detail. Arbitrary numbers, like the SWGFAST 1,000 PPI help us to guarantee that we are capturing enough detail, but we also need to understand that resolutions less than those recommendations don’t somehow become useless.

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What’s Different in Photoshop CS4?

Nov 3rd, 2009 - Filed under: Photoshop

When I wrote the book, Photoshop CS3 for Forensics Professionals, I argued with my editor about the title (I didn’t want to list the version in the title). I included ways to do just about every technique in the book using earlier versions, and it’s so rare that Adobe discards a feature that I was pretty certain that it would be applicable to future versions of Photoshop. In addition, my experience tells me that most law enforcement agencies (the primary audience for the book) don’t upgrade with each version, so most agencies using Photoshop may never see CS3. Well, I lost the argument, and now I frequently get asked about differences in CS4, as well as applicability to earlier versions. Before continuing, let me say that the book is as relevant to CS4 and CS2 and CS as it is to CS3.

Two of the most obvious changes for forensics users are the missing Contact Sheet and the Layer Comps to PDF features. The Contact Sheet feature can be downloaded from Adobe for the Mac or Windows and installed into CS4, so there’s no need to panic. You can also create contact sheets with some greater capabilities using the Output workspace in Bridge. And, the Contact Sheet X script written by X Bytor works in CS4. Regarding Layer Comps to PDF – well, that will just take two steps now – first, use Layer Comps to Files, then create a one image per page contact sheet with the results.

Another obvious change is in the interface – Photoshop will now open images as tabs, similar to web browsers. Some users seem to love this, and it drives others crazy. I’m one of the ones who prefers the old method. To get rid of the tabs view, choose the Interface Preference and uncheck the “Open Documents as Tabs” and the “Enable Floating Document…” check boxes. You’ll be back to the way things were.

How about that Adjustments panel? This is new, as is the Masks panel. These make it easier to create adjustment layers and to modify masks. There is no need to go to the Layers panel, click on the Adjustment Layers icon, choose the type of adjustment layer you want, make your settings, then click an OK button. Now you can just select the type of adjustment in the Adjustment panel, make your settings, and you’re done. Note that it’s best to keep the Adjustment Panel and the Layers panel staggered on two different columns and at different heights so that they don’t cover each other when bouncing back and forth between them.

CS4 also added Smart Filters. This provides similar capabilities of Adjustment Layers to Filters. If you first convert your image to a Smart Object, you can apply filters and re-edit them, just as you can an Adjustment Layer.

There are a handful of other differences between CS3 and CS4 – but these are the significant ones for forensics users. That said, one of the best places to learn about many things Photoshop is from John Nack’s excellent blog. John is senior product manager for Photoshop and he frequently posts great information about changes to Photoshop, and he asks users for feedback. John even takes criticism of Photoshop well – as shown in his post to my comparing Photoshop to the Johnny Cash song, “One Piece at a Time.” I read John’s blog every morning when starting my day.

I’ll post a Photoshop tip now and then here. If anyone has any questions about a feature or method, post a comment and I’ll try to address it.

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