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Thread started 01 Feb 2018 (Thursday) 16:19
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help, please <3 - I am a Geologist struggling to find the proper camera settings (Canon Rebel XT)

 
Kat9055
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Feb 01, 2018 16:19 |  #1

Hi, my name is Kat and I am a geologist with a small, environmental consulting firm. I work at a drill-site, where I take photos of sediments (dirt...) every 5-ft, using a camera stand to make sure the photos are consistent. We use a gray card in every photo and a Canon Ring Flash. We post-process the photos using Photoshop.

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I am newly in charge of post-processing these photos and they are INCREDIBLY inconsistent! My problem is that there are several geologists and although we all use the same model camera, because of light changing with weather and throughout the day, user error (I have some older coworkers that struggle with technology), and camera settings, our photographs often are dark and blue tinted, or sometimes over-exposed using the same settings.

I have been trying to learn what I can to find the best settings, but my supervisor wants to use only one setting that is unchanging, despite changing environments, otherwise, she thinks the photos will be too inconsistent among different geologists.

Is there a setting I can use that will reduce the amount of post-processing (especially color)? Or any other advice??

Here are some examples of samples taken from the same camera with the same settings:

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Thanks for any help or advice!!!



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Dusty
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Post has been edited 22 days ago by Dusty.
Feb 01, 2018 16:25 |  #2

Open your image in Photoshop.
Go to Image tab.
Scroll down to 'Adjustments', then choose 'Curves'.
When this opens pick the middle 'eyedropper' and then click anywhere onto the Grey Card in your photo.
Click ok.
Done.

Dusty.
:-)

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Dusty
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MalVeauX
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Post has been edited 22 days ago by MalVeauX.
Feb 01, 2018 16:27 |  #3

1) Stop using ETTL / Automatic exposure flash. Use manual flash power setting. Distance from flash to subject is constant, so exposure will be constant.

2) Set white balance to be Flash (little bolt symbol).

3) Camera mode set to Manual. Set focal-ratio (f-stop number) to be a constant value for depth of field purposes (such as F8 or F11). Set shutter to sync speed (1/200s). Set ISO to whatever (ISO 100, 200, 400). Pick one set of these and leave it there forever. Example, 1/200s, F8, ISO 200. Then get your flash exposure (again manual output) and whatever it is (example, 1/4th power), adjust until you are happy with the exposure, then leave it there. You're good to go as long as you do not change distance to subject.

Very best,


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Bassat
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Post has been edited 22 days ago by Bassat.
Feb 01, 2018 16:31 |  #4

Set the camera to MANUAL mode. Set the FLASH to MANUAL mode. Yes, those are two different things. Set the shutter speed to whatever your camera's X-SYNC speed is, likely 1/200. Set the aperture to f/8. Set the ISO to 400. Set White Balance (WB) to FLASH.

Set the flash to full power. Take a photo. It will likely be too bright. If so, turn the flash down to 1/2 power. Take a photo. If it is too bright, turn the flash down to 1/4 power. Repeat until you have the exposure you want. Once you get close, I believe your flash is adjustable in 1/3 stop increments. If desired, you can dial in the specific output level you need. If it doesn't have 1/3 stop, full stops (what you started adjusting 1, 1/2, 1/4, 1/8...) will do. From there you can adjust the brightness in your post-processing program.

Once you have the proper settings dialed in, write them down. That will save doing all this again.

EDIT:
Mr. Wise obviously types faster than I do. :)


Tom

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Bassat
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Feb 01, 2018 16:33 |  #5

Dusty wrote in post #18554248 (external link)
Open your image in Photoshop.
Go to Image tab.
Scroll down to 'Adjustments', then choose 'Curves'.
When this opens pick the middle 'eyedropper' and then click anywhere onto the Grey Card in your photo.
Click ok.
Done.

Dusty.
:-)
thumbnailHosted photo: posted by Dusty in
./showthread.php?p=185​54248&i=i114499572
forum: Canon EOS Digital Cameras

DO NOT ATTEMPT THIS. IT WILL NOT WORK.

This looks simple. It is not. And it won't work. You MUST dial in the ISO, WB, and FLASH OUTPUT to get consistent results IN-CAMERA. Fixing every photo in your post-processing program is what you are trying to AVOID.


Tom

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Dusty
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Feb 01, 2018 16:45 as a reply to Bassat's post |  #6

True, getting it right in camera is ideal.
But the OP can use this to fix the ones taken already.

:-)


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Bassat
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Feb 01, 2018 17:00 |  #7

Dusty wrote in post #18554257 (external link)
True, getting it right in camera is ideal.
But the OP can use this to fix the ones taken already.

:-)

Good point. I hadn't considered the need to fix previous photos. DOH!!!! :)


Tom

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Kat9055
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Feb 02, 2018 13:43 as a reply to Dusty's post |  #8

Thanks, this is currently how I am post-processing the photos (the ones included in the original post are in RAW), but the very dark/very light or very blue photos, this leads to more noise than we want in the finish product or sometimes washed out images. Any advice on reducing that or possibly removing it in the post-processing?




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Kat9055
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Feb 02, 2018 14:12 |  #9

Thank you so much for the responses. I really appreciate the advice. Okay, this will definitely prove how new I am at this: I know how to set the focal-ratio, shutter speed, and ISO, but I know very little about the flash settings. When I was trained they basically said, "don't touch any settings".

Is there a crash course somewhere on flash and manual flash power settings?

MalVeauX wrote in post #18554252 (external link)

Then get your flash exposure (again manual output) and whatever it is (example, 1/4th power), adjust until you are happy with the exposure, then leave it there. You're good to go as long as you do not change distance to subject

Bassat wrote in post #18554252 (external link)
Set the flash to full power. Take a photo. It will likely be too bright. If so, turn the flash down to 1/2 power. Take a photo. If it is too bright, turn the flash down to 1/4 power. Repeat until you have the exposure you want. Once you get close, I believe your flash is adjustable in 1/3 stop increments. If desired, you can dial in the specific output level you need. If it doesn't have 1/3 stop, full stops (what you started adjusting 1, 1/2, 1/4, 1/8...) will do. From there you can adjust the brightness in your post-processing program.

Once you have the proper settings dialed in, write them down. That will save doing all this again.

How do I do this? I set the white balance to "Flash", but I am not sure how to proceed from here. Is this something I need to do on the Canon Macro Ring Lite MR-14EX, or is this something I change in-camera?

Thanks again everyone, you are teaching me loads!




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Kat9055
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Feb 02, 2018 14:13 as a reply to Dusty's post |  #10

Thanks! Luckily, I know how to post-process using curves. I am thinking I will probably become a lot better at the post-processing now that I am starting to understand more about how the camera and settings work.




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Bassat
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Post has been last edited 21 days ago by Bassat. 2 edits done in total.
Feb 02, 2018 15:08 |  #11

Kat9055 wrote in post #18554849 (external link)
Thank you so much for the responses. I really appreciate the advice. Okay, this will definitely prove how new I am at this: I know how to set the focal-ratio, shutter speed, and ISO, but I know very little about the flash settings. When I was trained they basically said, "don't touch any settings".

Is there a crash course somewhere on flash and manual flash power settings?

How do I do this? I set the white balance to "Flash", but I am not sure how to proceed from here. Is this something I need to do on the Canon Macro Ring Lite MR-14EX, or is this something I change in-camera?

Thanks again everyone, you are teaching me loads!

You will need to set the MR-14EX with buttons on the flash. Getting into MANUAL mode is extremely complicated, so follow these directions PRECISELY:

1.) Turn on the flash.
2.) Press the MODE button until M appears at the left side of the back panel on the flash.

Done!

To the right of the M will be a number such as 1/1, 1/4, 1/16. That is the current power setting. It really doesn't matter what it is set on to start with.

Take a photo with everything (camera, stand, aperture, rock pan, shutter speed, ISO (start with 400)) set up the way you will use it.

If it is too bright or too dark:
Press SET/SELECT (on the flash) so the above number (1/4, 1/32, whatever) flashes.
To fix too bright, use the button below the minus '-' sign to lower power.
To fix too dark, use the button below the plus '+' sign to raise power.

If you can't get the photo bright enough, raise the ISO (on the camera).
If you can't get the photo dark enough, lower the ISO (on the camera).

The MR-14EX is NOT adjustable in 1/3 stop increments. One you get the exposure dialed in, you can make any last minor adjustments to exposure in your post-processing program.

A few more tips. Use the fastest (x-sync) shutter speed your camera will do. (IIRC, that is 1/200). Use a small aperture like f/8 to f/11. F/5.6 may do it. Start with f/8. The intent of fast shutter and small aperture is two-fold. Primarily it gets you a sharp(er) photo with enough depth-of-field to see what you have photographed. Secondarily, it forces the exposure to rely completely on the flash, overpowering any ambient light in the room. That ambient light (and inconsistent exposures) is causing the erratic color casts in your posted photos.

Dont' forget to use MANUAL mode on the camera, a fixed ISO value, FLASH WB, and write down all the setting once you have it all dialed in. Happy shooting!


Tom

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Kat9055
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Feb 02, 2018 15:40 as a reply to Bassat's post |  #12

You are so awesome!!! This is just what I needed. I will try this next week on my samples!!! Thanks so much!!




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Dusty
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Feb 02, 2018 17:30 as a reply to Kat9055's post |  #13

Getting exposure right in camera will go a long way in reducing noise.
Great advice given from the others in setting up the camera and flash.
If you need noise reduction in post, I hesitate because I'm not a big fan of PP NR, but you could try Neat Image.
I've not kept up with the latest as I've been out of the game for a while but try the Neat Image Plug In for PS.
Others may recommend something better.
Cheers
Dusty.

:-)


Dusty
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davesrose
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Post has been last edited 21 days ago by davesrose. 3 edits done in total.
Feb 02, 2018 18:38 |  #14

Hi Kat, I can see that other major complications are coming from several geologists using the camera and flash setup. You mention some of your colleagues are older and aren't comfortable with technology: hopefully, when you come up with your recipe, you can show and teach the others the proper functions of the camera.

From what you indicate, the camera setup is always 5 ft from the ground....with lighting conditions changing from the outside environment. I only shoot in manual mode on the camera with external flashes since I can define what ideal exposure I want (for DOF and ISO). It's then just a matter of raising or lowering flash light intensity. You can experiment with your work area to see what aperture gives you appropriate DOF (it may be a stop or so wider then f8 if your rocks aren't protruding out much): it's good to see what works for your situation. Shutter speed looks to be optimal at 1/200 for your camera's sync speed, and 400 ISO is generally considered a default outdoor/cloudy speed. The more exposure your camera has (wider aperture, slower shutter, higher ISO), the less dependency on the flash's output. If you're not using full power, the flash will refresh quicker and the exposure is using more ambient light. Others will raise shutter speeds (and go into high speed sync), if they want to isolate the light's source and take out ambient light. It doesn't look like your situation will require that....so keeping ISO 400, shutter 1/200, and seeing what aperture gives best DOF will be the settings you should always have set on the camera. I would then design a how to sheet (like the previous sheet on the flash setup). Maybe even try to get fancy and use close up photos, or grab diagrams from manuals, to visually show how to set the camera in manual and change the aperture, ISO, shutter to your specified settings. It can still be easy for another user to accidentally change a setting: so making sure that everyone knows the basics of manual settings is still important.

I don't know if you want to get into custom WB, but that can also make photos more consistent: require less time processing (since the scene's WB is a mixture of flash and ambient light). It would require a person to set WB each time they're in a new environment and have changed the flash power setting, though, so you'd have to see if its too complicated for your coworkers. Here is Canon's manual on the custom WB mode for the XT:

How to set a custom white balance on the EOS Digital Rebel XT (external link)

As Bassat indicated, once you've figured your camera settings, keep the flash in manual and all you need to do is raise or lower the flash's power. Perhaps you should also have a few properly exposed photo examples, to be sure your coworkers are setting the flash power for best exposure as well.


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Wilt
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Feb 02, 2018 19:00 |  #15

davesrose wrote:
From what you indicate, the camera setup is always 5 ft from the ground....with lighting conditions changing from the outside environment. ... It's then just a matter of raising or lowering flash light intensity.

To analyze this situation for you, Kat...

The Canon MR14-EX has a Guide Number (at ISO 100) of 14m...that is GN (at ISO 400) of 28m; that is GN46' at ISO 100 or GN92' at ISO 400...so if you shoot at a fixed 5' distance from subject, then

  • at full power on the MR14-EX, the f/stop should be f/518.4 (f/16 + 0.4EV)., (GN92' / 5' = f/18.4)
  • at 1/4 power on the MR14-EX, the f/stop should be f/9.2 (f/8 +0.4EV) (GN44' / 5' = f/9.2)

The problem is that in bright sun ISO 400 requires 1/400 f/16 for ambient light-only exposure, or 1/200 f/22 for flash-compatible shutter speed.
Even in the shade ISO 400 requires 1/400 f/5.6 for ambient light-only exposure, or 1/200 f/8 for for flash-compatible shutter speed


  1. So in the bright sun, the flash cannot output enough light falling short of equalling the sun by -0.5EV difference, and
  2. in the shade the flash overpowers ambient by 1.4EV.
So the issues of inconsistent White Balance are NOT going to be overcome via the use of the MR14-EX when in the sun.

You need a higher power flash in order to utilize a light source which can overpower the sunlight or even shade... at distance of 5' the MR14-EX is otherwise useful only in the shade..a more powerful flash unit is needed with power equivalent to GN160 to get f/32 and overpower the sun . Fortunately bright sun is pretty consistent in WB value, so the MR14-EX would like be suitable for shade, while you can rely on bright sun for consistent WB.

For those who scoff about the need to understand Guide Numbers in the days of eTTL, this is a primary example how you can -- in advance -- figure out the impossibility or practicality of a situation when you understand Guide Number!

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help, please <3 - I am a Geologist struggling to find the proper camera settings (Canon Rebel XT)
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