CanonEOSII RebelT7i modified UV-IR . Using a Canon 18-55mmLens . With this experiment , I used a gray plate from Dollar Tree for $1.00 and out side I put the plate on a bench to photograph it for "Custom White Balance" images as 'one-shotColor' using RAW in the DSLR . The first image of each filter type was done as "Daylight" white balance , and the second image of each filter type was done as the 'Daylight' image used in the "Custom White Balance" option in the DSLR's Menu and then for "White Balance" , the 'Custom' icon was used instead of the 'Daylight' icon ... which seems to turn the image to a 'gray' color ... showing the plate being used as 'gray' . This experiment should be done with the Canon DSLR as a stand-alone imager without being hooked to a laptop so the LCD screen can show the results and be able to use the images for the "Custom White Balance" option . Why I did this experiment, which was during an overcast cloudy sky , but , how it should be done is with the Sun overhead at about Noon on a clear day .... according to a web page on [ DeepSkyStacker ] about using an 18% gray card for white balance while using a modified DSLR due to the 'red' hue existence which causes the DSLR's 'stock' version for the 'White Balance' icons to be wrong .... so you must fix that with a "Custom White Balance" option proceedure . {{{{{{{{{{{{{{{{{{{{ This area I copied from 'Using Deep SkyStacker' thru Astropix.com and shows that something must be done about a modified DSLR and also using filters . Basics Start with reasonable-quality images that are correctly exposed, focused and tracked. The program will have trouble aligning images if they are not. It is important to shoot raw files for correct calibration. It is also helpful to have light frames that are shot with the correct color balance to start with, especially if you are using filters or have a modified camera. This can be accomplished as follows: Unmodified camera – shoot daylight white balance in the camera. Modified camera – shoot a custom white balance in the camera set on a gray card illuminated by the sun at noon on a clear day. Light-Pollution filters – shoot a custom white balance in the camera for both modified and unmodified cameras with the filter in place. }}}}}}}}}}}}}}}}}}}}}}}}}}}}]]] Adjustment applied to it in the camera like JPEG images. However, there are notations, called tags, that are included in the raw files, that describe what white balance the camera was set to when the image was taken. When a raw image is opened in the camera manufacturer's dedicated image processing program, such as Canon's Digital Photo Professional, or Nikon View, the embedded tag is usually applied as the default white balance setting. This setting can easily be changed for the raw file in this software or if the raw file is opened in Photoshop. Standard white balances, such as daylight, can be applied. With a stock, non-modified camera, all we need to do is simply select daylight as the white balance for the deep-sky image. Daylight White Balance will not work however for modified cameras because their settings are configured with the manufacturer's long-wavelength filter in place in front of the sensor. With a modified camera, we can shoot a custom white balance as a work around. Shooting a Custom White Balance Use a digital gray card directly illuminated by sunshine on a clear day at noon with the Sun high in the sky. You can also use a white piece of paper. Fill the frame with the card or piece of paper. Do no let your shadow fall on the card. Use raw file format. Use auto exposure and take a picture of the card. Select this card in your camera's menu to use as a custom white balance. Read your camera's manual to find out exactly how to do this as it is different for different cameras. Use this custom white balance to shoot another picture of your gray card or white piece of paper, again on auto exposure, as a test to be sure your custom white balance is working. It should come out gray. For the obsessive compulsive like me, you should use a spectrally uniform gray card to shoot a custom white balance. White paper can have ultra-violet brighteners in it that may throw off the custom white balance. When you use auto exposure on a white piece of paper, it will not be white, it will be underexposed. This is correct. On a modified camera it will probably also be red, and this is also correct. This red color is what the custom white balance will correct. It is ok to use something like a 50mm lens to shoot the custom white balance. Then use that custom white balance when you shoot through the scope, or with another lens, if you are using that same filter. If you plan to shoot with a light-pollution filter, you should use that on the camera when you shoot the custom white balance. The white balance that you use in the camera, stock or modified, to shoot the gray card in the sunshine does not matter because the camera will set the white balance on the raw data. Store the picture file of your gray card on an old memory card and keep it with you. That way, if you change the custom white balance, you can re-apply it at night at the telescope without having to shoot it again in the sunshine. Follow your camera's instructions for shooting a custom white balance. This frame is then selected in the camera's custom white balance menu. The camera then sets the white balance for all subsequent images shot with this setting as standard. This custom white balance information is stored in the metadata that accompanies each image file that is shot with it. Programs like Images Plus will apply this custom white balance to the raw file when it is opened. \\\\\\\\\\\\\\\\\\\\\\\\\ .x I will redo these filter images done thru a Lens on a clear day soon to use thru the Telescope for Deep Sky imaging and with the narrowband filter images for "Custom White Balance" I will see if renders an image a grayish color or not ... but using a suffix when using MaximDL Pro I will be about to tell which images are done with what filter ,like , UHC or OIII if I had an OIII , and Ha , and SII ... because there is a narrow amount of color being acquired and the images might look 'gray' but they will be used to create a 'false color' image anyway .x +++++++++++++++++++ Why the web pages say to use a 'gray' color or card is to get the 18% gray area in an image which is between black and white .... if you don't get a "Custom White Balance" into the "White Balance" 'Custom' icon and use another icon instead ... the DSLR will try to create a mix of colors which will most likely over-saturate trying to get the best 18% gray color area it can and it most likely won't do it , so creating your own "Custom White Balance" image options will hopefully improve Deep Sky imaging with a modified DSLR . The scene across a field was done with a Lumicon Minus-Violet filter as a before image at 'Daylight' icon and an after image using the 'Custom' icon which removes some of the 'yellow' tint of the Minus-Violet filter .x +++++++++++++++++ .x Plus +++ the Horsehead Nebula image was done with a "Custom White Balance" option using an image of a 'black card' poster board and then the "White Balance' 'Custom' icon was used . This reduced the 'red' hue that is strong in the image when using the 'Daylight' icon or any of the other icons .x
CanonEOSII RebelT7i .... modified UV-IR @ Hutech . This means it is no longer a 'stock' over-the-counter consumer DSLR for normal daytime pictures . Using a Canon 18-55mm Lens without any filter in front of the Lens . The R.Reeves book a 2006 version 'Introduction to Digital Astrophotography' says that a modified DSLR no longer has the original 'icon' "White Balance" color conversion settings because a strong 'red' hue is also in the images due to the allowed extra 'red' light waves past Hydrogen Alpha 656nm . So , then you would have to make adjustments to taste . But , I have looked on the 'GOOGLE' Search and found 'Deep SkyStacker - 18% Gray Card' reviews which will take you to 'AstroPix to a 'Basics' section with a link for modified DSLRs and that explains why you would use a 'Gray Card' with filters . Further searching showed that for night photography ... you would use a 'Black Card' earlier in the daytime and at least 'spot-meter' on the black color .... so , I use the Lens without a filter at ISO100 and the Lens stopped down to f/25 for a dim exposure on a cloudy day outside . This image is the result of a 'Balck card' poster board from Dollar Tree for $1.00 .... but I also spray painted it with Rust-o-leum Stove High Heat Black paint which is a suggestion in MaximDL Forums that has a black pigment instead of a dye and reflects a minimum amount of a nanometer around the 700nm area which reflects a white light off of anodized coatings which probably use a dye in the paint . The spray paint leaves dark and light areas , so , I 'spot-metered' on a darker area . To do the 'Black Card' image ... I use the 'Daylight-icon' in the "White Balance" option of the DSLR's Menu and set to ISO100 and turn on 'LiveView' and look at the 'Black Card' at a long Zoom focal-length which in this case is 55mmFL . Then 'focus' on a label on the card and then put it out of focus so it's blurry . Then use an exposure ... which in this case was 1/5th of a second . You want the image dark and not showing the little bar code label ... that's why 'spot-metering' is useful on a dark area Then press the shutter button down halfway and let the data in the 'LiveView' calculate and then fully press down the shutter button and the exposure will be taken . Wait about 10 seconds and turn off the 'LiveView' and then open the image into the LCD screen and then open the Menu for "Custom White Balance" and allow with the prompts to use the open image as the "Custom White Balance" and then go to the "White Balance" option and toggle to the 'Custom-icon' and press OK and then close the Menu options and thake another 'LiveView' image the same way as before with the 'spot-metering' little round circle in the 'LiveView' screen and press the shutter button halfway to 'meter' and press the button fully all the way and the image will be taken . Wait about 10 or more seconds and close the 'LiveView' and then open the just taken image which should be very dark and just slightly visible and use the image for the "Custom White Balance" Menu option . This image should be better than the first one because any 'red' hue will be removed and only 'black' will be the 'Custom-icon' "White Balance" color conversion data . With this image as the 'Custom-icon' ... you can do daytime images that are real close to the real visual colors that you see with your eyes . This also works OK on Deep Sky Photography like the Horsehead Nebula ... that has smoke that is light in color without the strong 'red' hue of the 'Daylight-icon' or other 'icons' like Shade or Cloudy or Auto .... because they are now altered by the modification of the DSLR . The 'Daylight-icon' image of the privot is a little redder than a visual look , the 'Custom-icon Black Card' image of the privot looks more normal with 'green' being almost exactly like a visual look . The 'Black Card' shows what it looks like that you use in the "Custom White Balance" option of the RebelT7i Menu .x
