Compact Canon CDHK RAW & Lens Distortion

[EMULAT3D]

No prob guys! That's what's so great with these forums, everyone helps each other.

Also, Chad we use CHDK on our cameras and works perfect with the hubs. Just make sure the remote trigger is set to "Two Push". This allows for the first push to focus and second to fire.

[chadfx]

Agreed, these forums are the best!

For my remote settings, I've got mine set to 'One Push' for my trigger type and it seems to work fine.

I did a quick test with the USB hub (already connected to the powered on camera).  I just plugged in the power for the hub and the camera locked focus, then pulled the power and the shutter was triggered. It's similar to how I have my basic remote switch set up. The switch is normally 'open' or not connecting the voltage circuit, then I press down (and hold) to 'close' the circuit and supply power over the USB line, which is the 'one push' to do the half press focus lock. When I release the pressure on the switch, it opens the circuit, breaking the voltage connection and initiating the 'full press' and taking the actual photo.

Here's the definition from the CHDK site:

http://chdk.wikia.com/wiki/USB_Remote

OnePush
Used with simple switch inputs. Pressing the switch initiates a "half-press" state. Releasing the switch initiates a "full-press" state for 100 mSec. There is no mechanism to cancel a "half-press" once this sequence is started. Also note that the "half press" will timeout after 10 seconds even if USB power is still applied.

TwoPush
Used with simple switch inputs. Pressing the switch initiates a "half-press" state. Releasing the switch and then immediately pressing the again switch in less than 1/2 second initiates a "full-press" state. Full press state continues while the switch is held. Failing to immediately press the switch the second time will cancel the sequence.

[chadfx]

One other note about this that is VERY important if you want to be able to download the RAW files over the USB connection. (you can save the frustration I ran into over this, where none on the DNG files were showing up over the USB connection, only when using a card reader...argh!)

http://images2.wikia.nocookie.net/chdk/images/8/84/CHDK_UserGuide_April_2009.pdf

CHDK RAW and DNG ?les can be downloaded to a computer with the USB cable under the
correct conditions; Instructions from CHDK forum senior member fe50:-
• disable remote in Remote parameters
• use .CR2 as ?le name extension (set up in the CHDK RAW menu)
• before you connect the camera to the computer's USB port you must power off and power on
the camera (important !)
• connect the camera, do not use the Windows transfer assistant - open the Windows Explorer,
• transfer (copy, e.g. with drag & drop or cut & paste) the images to your hard disc.
Mac users - use Image Capture or Canon Camera Window to open when camera is detected.
You can also transfer RAW images in the DNG format this way, but you must use .CR2 ?lename
extension in CHDK; after transferring the ?les you have to rename them (give them the correct
extension - .DNG **).

** and my footnote that I don't think you have to change the CR2 extension back to DNG once they are copied over to the computer (at least not with Adobe Bridge/ACR on the Mac, as it appears to treat them exactly the same)

[chadfx]

(oh, and just a small complaint that it's all still a bit tedious, because you still have to turn the remote USB remote function off for EACH camera to be visible over USB,  and also power cycle EACH camera to make the DNG RAW files visible(and don't forget to turn the remote triggering back on when it's time to shoot again!)...but hey, what are you going to do?) 

=)

[andy_s]

...then connect the hub to the PC to retrieve images (via Windows Picture Import). This is nice because you can then tag the images to a specific camera number.

I hope to develop a file/directory download interface that is very flexible [including tagging image to the specific camera and maybe directory = customer_number].

Might someone further comment:

why is it nice to relate image to camera ? [is it useful in automation with python for example ?]

fmi:

• home: http://www.cybercom.net/~dcoffin/dcraw/ note SX150IS is not on list
• dcraw http://ij-plugins.sourceforge.net/plugins/dcraw/
• Batch Processing with DCRaw plugin @ Batch Processing with DCRaw plugin

[borgy168]

Hello Guys,

I am glad to have read all your experiences using Raw DNG to JPG.  And Thank you in advance for answering my questions.

I tried shooting in RAW using a CHDK Canon A2300 and compared the result of DNG converted to 100% JPG and the JPG from my canon camera.  I tried 2 batches for the RAW DNG. 1.) unedited converted to JPG and 2.) edited - shadows/highlight contrast but did not touch the noise/ sharpness.  Basing on the output from PS, it seems that JPG from my canon camera has a superior quality than RAW.

How can I maximize the output of my 3d model using RAW DNG file for PS use? 

Is the RAW file generated from A2300 less superior than other P&S models?

Any feedback is helpful :-)

Cheers,

Borgy

[chadfx]

Hi Borgy, I can't say exactly why you are seeing these differences in the PS computations. When I did my initial RAW vs JPG comparisons, it was only on individual photos and not through the entire PS pipeline. I haven't done much testing with this setup since them, sorry. I'm not if I ever really compared the results as you have here. It's certainly possible that the camera JPGs are a better fit for PS processing.

When you are converting your images from RAW, there are some additional adjustments might be helpful, such as noise reduction, which is likely happening in the camera's JPGs. I would probably suggest starting from a comparison of the photos themselves and verifying that a converted RAW image actually does look better than the camera's JPG. Hopefully that would improve your PS results. There are also a number of different RAW conversion tools, some better than others. I am usually doing this with Adobe's Camera Raw (or Lightroom)

Cheers,  Chad

[borgy168]

I did a lot of comparison with my A2200 and it seems that JPG conversion from Canon gave me better points.  I tried some noise reduction tool but I got hole on the nose of my model.  Maybe there is something wrong with the way I process the Raw. 

Anyway,  Thanks Chad! Appreciate the feedback.

[bigben]

If I am using CDHK with a Canon compact camera (A3300 IS) and shoot in DNG raw, it does not automatically correct for the lens distortion...so it appears different from the JPGs coming out of the camera. ...

On this part of the original question...  I wouldn't do any distortion correction prior to using Photoscan as you can either provide calibrated values to Photoscan or have it calculate distortion parameters for you.   If the image offset calculated by Photoscan is different to that used in the in-camera correction then you will effectively be using distorted images.

[chadfx]

That makes sense, thanks. I know that outside perspective correction is a usually a strict no-no for Photoscan. It sounds like it will figure it all out on its own either way (camera corrected JPGs or uncorrected RAWs). I certainly haven't had poor results from the RAWs, but it would be worth a comparison at some point I suppose (if only time were more plentiful...sigh)

[bigben]

Photoscan will figure "something" out regardless but not neces4444444sarily "it"... eg. you can feed it fisheye images and process them as rectilinear and it will figure something out.  The calculations for lens distortion are all done from the optical centre of the image.  If you in-camera correction does this on the geometric centre of the image file and the optical centre of the image is in a different position to this then the final result will be technically distorted, resulting in a mathematical best fit of all of the criteria put together. As a result, camera positions and rotations will also have small errors, compensating for the incorrect distortion correction and you'll see more noise in the sparse point cloud.

If you want a comparison, try creating unfiltered dense clouds.