How to Use an Expodisc With Studio Lights

Using an Expodisc when photographing people, pets or objects in the studio, will give your pictures true to life color and white balance accuracy. The filter sized device is compact, and easy to transport when using studio lights on location. Photographs created in the studio or on location with the use of an Expodisc make post production a breeze by eliminating time consuming color corrections.

Step1Set up studio lighting. Arrange the lights in the studio or on location in preparation for the photography shoot. Do a few test shots to test the lights, making sure they are firing in sync. Set the correct exposure on your camera as you normally would in a studio set up.

Step2Change the settings on your SLR camera. Find your white balance settings and select the custom white balance icon. On a Canon Digital SLR camera, the icon resembles two studio lights with a person in between. Use the cameras owner’s manual to correctly identify the icon used by your camera system.

Step3Turn off the auto focus feature on your digital SLR camera. Locate the toggle button on the side of your lens or base of your camera body. They are usually labeled AF for auto focus and M for manual focus. Select the manual mode.

Step4Remove the Expodisc from its case. If your Expodisc is the same filter size as your camera lens, use the threaded mount to attach the Expodisc to the lens. If the Expodisc is larger than your lens, simply hold the Expodisc in front of the lens. If you Expodisc is smaller than your camera lens, you need to purchase a larger Expodisc.

Step5Move to the middle of your studio lighting set-up. Position yourself where your subject will be that you are photographing. Point your camera at your main studio light that will be illuminating your subject. If you are using a broad-lighting technique, and have two main lights, select the one that is closer to another light source, such as over head lighting.

Step6Take a picture with the Expodisc covering your lens. Do not try to focus your lens. You will see a fuzzy picture through the lens, and your recorded image will be a grayish-white square. Go into your camera menu system and find the custom white balance setting. Select the photo you just took with the Expodisc as your standard for the custom white balance. Turn off your menu system, and proceed with your photography shoot. You have successfully set a custom white balance using studio lighting with an Expodisc.

FAQ - Frequently Asked Questions

Look through the list of questions below for assistanceGeneral

1. How does the ExpoDisc work as a white balance filter?

2. How do I know which size ExpoDisc to buy? And do I need an ExpoDisc for each lens?

3. Can the ExpoDisc be used in conjunction with other filters?

4. Can I use the ExpoDisc to set a custom white balance if the manufacturer recommends a white card, rather than a gray card?

5. Is the ExpoDisc useful when shooting in the RAW file format?

6. Will the ExpoDisc diffuse detail in photographs?

7. If I set a custom white balance with one lens and switch to another lens do I need to set a new white balance?

8. What is the difference between the ExpoDisc "Neutral" and the ExpoDisc "Portrait" filters?

9. By how many degrees Kelvin is the color temperature increased when using a Portrait ExpoDisc versus a Neutral ExpoDisc?

10. What is the difference between the ExpoDisc "Classic" and the current ExpoDisc model?

11. What is the difference between the ExpoDisc and the ExpoCap?

12. How is the ExpoDisc hand calibrated?

13. What kind of warranty comes with the ExpoDisc?

Camera

1. Do I need to set a new custom white balance when I change my exposure?

2. Will the ExpoDisc work with my camera?

3. How does an ExpoDisc differ from a gray card?

4. Why do I need to switch my focus to manual to set a custom white balance?

5. Does it matter which exposure mode I use when setting a custom white balance?

6. What white balance setting do I use when I take my custom white balance reading?

7. Do I need to save the custom white balance reference image?

8. When trying to set a custom white balance my camera keeps giving me the "no good" error message. What am I doing wrong?

9. When trying to set a custom white balance my camera keeps giving me the "out of range", "over", or "under" error messages. What am I doing wrong?

10. Why won't the 4x4 ExpoDisc fit into my Lee Filter holder?

Lighting

1. Do my manual exposure settings (shutter speed and aperture) matter when taking a custom white balance while using strobes?

2. How do I use the ExpoDisc with a flash unit?

3. My pictures have a blue colorcast after setting a custom white balance. What did I do wrong?

4. How do I set the white balance when the subject has his/her back to the sun?

5. How do I set a white balance in mixed lighting situations?

Video

1. Does the ExpoDisc work with digital video cameras?

Underwater

1. Can the ExpoDisc be used for underwater photography?

OR... click here to ask your own question using our contact form.

General

1. How does the ExpoDisc work as a white balance filter?

  The ExpoDisc transmits 18% of light in the visible spectrum through to your camera’s film or image sensor. Much like a traditional gray card, the resulting featureless image, or 'gray frame' that is captured through the ExpoDisc represents the average color of light at the physical location of the ExpoDisc.  By setting a custom white balance digital cameras can effectively compensate for, and neutralize the color of light represented in the 'gray frame', resulting in good color balance for that particular light source.

2. How do I know which size ExpoDisc to buy? And do I need an ExpoDisc for each lens?

  We recommend for ease of use and accuracy that you use the ExpoDisc that corresponds to the actual filter size of your lens.  It is more convenient if the filter fits your lens because it allows the use of both your hands, and prevents any possible light leakage past the ExpoDisc.  Filter sizes are measured in millimeters, e.g. ∅58mm, ∅67mm, ∅77mm, etc., and are usually printed on the end of the lens barrel.

If you cannot find an ExpoDisc that fits your lens, or if you only wish to purchase one filter, then you can buy a larger size and simply hold it in front of the lens.  If using a larger ExpoDisc over a smaller lens, you must hold the ExpoDisc flat over the end of the lens to prevent any light leaks.

We do not advise using a smaller sized ExpoDisc in front of a larger sized lens.  If the ExpoDisc you are holding in front of your lens is too small, you run the risk of setting an incorrect white balance by allowing unfiltered light to leak into the camera around the edge of the filter.

3. Can the ExpoDisc be used in conjunction with other filters?

  Yes. The ExpoDisc can be used in conjunction with other filters such as polarizing, skylight, ultraviolet, and color balancing filters when you keep the following caution in mind. A color cast can be introduced if: 1) you set a custom white balance with a filter (other than the ExpoDisc) on the lens and then remove the filter; or, 2) you set a custom white balance without a filter on the lens and then add a filter to the lens.

Example: If you set a white balance with a Wratten 81A filter on the lens the camera will assume that the source light is too warm and will add blue. As long as the 81A filter is still on the lens the blue that is added by the camera will be negated by the warmth of the filter. If you now remove the filter, the camera will still add the blue but there is no additional warm light to offset, therefore your pictures will have a blue cast.

Note: If you want to use a color balancing filter such as a Wratten 81A on your camera to "warm" up your picture, make sure you add it AFTER you set your custom white balance. Any color or color balancing filter on the lens when you set a custom white balance will be neutralized by the camera's white balance program negating the filter's effect.

4. Can I use the ExpoDisc to set a custom white balance if the manufacturer recommends a white card, rather than a gray card?

  Yes. The ExpoDisc reference image is usable by those digital cameras whose manufacturers recommend either gray, or white reflective surfaces for setting a custom white balance. 

An accurate custom white balance requires measuring the exact color temperature of light illuminating the subject. The

intensity of that sample light is not relevent, provided the sample is neither severely over, or under exposed. The ExpoDisc is calibrated for 18% light transmission, meaning a properly exposed reference image through the ExpoDisc will produce a usable 18% neutral gray.

5. Is the ExpoDisc useful when shooting in the RAW file format?

  Yes.  Using the ExpoDisc to set a custom white balance, even when shooting in RAW, can save valuable time in the post-production workflow process.  Set the custom white balance just as you would when shooting JPEG.  When downloading the RAW files for post production editing, select 'As Shot' for the white balance setting.  This will utilize the custom white balance set at the time of image capture, and will reduce, or eliminate the need for additional color correction on the image file.

6. Will the ExpoDisc diffuse detail in photographs?

  No. When using the ExpoDisc to set a custom white balance it is only on the lens while performing your camera's white balance procedure; afterwards it is removed. Since it is not used as an optical component while actually taking a photograph it cannot alter the lens or camera's normal resolution or ability to capture detail.

Note: A camera's ability to capture detail is dependent on the quality of the lens, other filters, exposure, and resolving power of the film or image sensor used while taking the photograph. Other factors may also effect the ability to reproduce detail in the final print such as the amount of manipulation and compression used in photo editing software, the amount of enlargement, the type of paper and inks used, and printer resolution.

7. If I set a custom white balance with one lens and switch to another lens do I need to set a new white balance?

  In most cases the answer is no, providing the lighting conditions have not changed. Most modern day lenses are optically clear and will not add any color cast that would affect the custom white balance if interchanged on the camera. However care should be taken to note if there are any filters on the lenses you are using. Skylight filters have a slight pink cast versus ultraviolet filters which are clear. If one lens has a skylight filter and the other a ultraviolet filter a color cast may be introduced. In addition, if one lens has a color balancing filter, like an Wratten 81A, and the other does not, a color cast will be introduced.

8. What is the difference between the ExpoDisc "Neutral" and the ExpoDisc "Portrait" filters?

  The ExpoDisc "Neutral" Filter is designed to be used in all photographic lighting situations where it is necessary to set a neutral white balance. It is the most versatile of the two filters. The "Neutral" Filter will produce images with white whites and gray grays.

The ExpoDisc "Portrait" Filter is designed specifically with the portrait photographer in mind. It produces a gentle warming effect, similar to what you might get using a Wratten 81A filter.

9. By how many degrees Kelvin is the color temperature increased when using a Portrait ExpoDisc versus a Neutral ExpoDisc?

  The color temperature increase is approximately equivalent to adding an 81A filter to your camera after you set a neutral white balance.  An 81A filter introduces a color adjustment of +18 mireds (micro-reciprocal degrees).  To determine the exact color temperature shift you will need to know the color temperature of the light falling on your subject.

Example:  If you are shooting a subject under lights balanced to a color temperature of 3400K and you add an 81A filter, the resulting picture will appear as if it was photographed using lights balanced for 3200K.  (Note: This was a common situation when using film balanced for 3200K [Type B] and you were shooting with lights balanced for 3400K [Type A].)  The change in the color temperature is 200K.

Using the following table you can do the calculation: 1. Find the Reciprocal Color Temperature for 3400K (294 mireds) 2. Add 18 to this number (294 + 18 = 312) 3. Locate the number 312 in the table and read the color temperature (3200K). 4. 3400K minus 3200K equals 200K

The color shift in degrees Kelvin will be different depending on the actual color temperature of the light you are balancing to.  For example, at 5500K the shift would be 500K (5500K to 5000K).

10. What is the difference between the ExpoDisc "Classic" and the current ExpoDisc model?

  The "Classic" ExpoDisc is the first design ExpoImaging produced for retail sales and distribution. The ring mount is made of a durable, black, molded plastic material.  The "Classic" model has been discontinued.

Current model ExpoDiscs incorporate significant improvements in design and materials. The filter ring has been upgraded to a more durable black anodized aluminum that includes a mounting system consisting of 3 tiny, spring loaded ball bearings. New testing and calibration equipment also enabled us to improve the formulation of the materials used in the construction of the ExpoDisc, resulting in improved neutrality and performance.

The new design and materials significantly improve the durability, consistency and fit of the new ExpoDisc over the previous plastic, "Classic" design.

11. What is the difference between the ExpoDisc and the ExpoCap?

  The ExpoDisc is intended to satisfy the high standards of demanding professional photographers.  Each ExpoDisc is hand calibrated to be 99% accurate for color balance.

The ExpoCap is designed for use by photographers who do not need the precision required by professional photographers.  Those amateur and enthusiast photographers who want better color, and better pictures, but don't need the accuracy of the ExpoDisc will appreciate the improvement in color achieved through use of the ExpoCap.  The ExpoCap will not provide a neutrally balanced image, but one that is gently warmed with 5 to 6 points of red and green (Photoshop Color Sampler Tool) on the image file.

This table highlights the differences between the ExpoCap, ExpoDisc Neutral and ExpoDisc Portrait filters:

 Features and Benefits  ExpoCap  ExpoDisc Neutral

 ExpoDisc Portrait

 Neutral (+/-2%)    

 18% Light Transmission  

 Set and Check Exposure (Middle Zone V)  

 Better in Mixed Light  

 Post Production Color Balance with RAW Image Files

 Produces Great Color on JPEG Image Files

 Easy Dust Identification

 Warmed Image File  

 Functions as a Lens Cap    

 Lanyard Strap Attached  

 Exposure and Printing Tool for Film   

12. How is the ExpoDisc hand calibrated?

  Each ExpoDisc is assembled by hand and individually checked for total light transmission and for light transmission neutrality at our facility in Watsonville, CA.

The target WHITE DENSITY RATING is 0.745 which corresponds to an 18% reflectance of incident light. This density (18% reflectance) falls within Zone V ± 1/6 f/stop. Zone V ± 1/6 f/stop has a range of 0.695 to 0.795. This information is printed on the card for the customers reference only. No adjustments need to be made.

The RGB numbers represent the density of light measured at specific wavelengths in the visible spectrum.  These numbers are intended only as a quality control mechanism to ensure that each ExpoDisc is within our specifications.

13. What kind of warranty comes with the ExpoDisc?

  All ExpoImaging products come with a limited warranty to be free of defects in workmanship and materials for a period one (1) year from the date of original retail purchase. If the product proves defective within the warranty period it will replaced. Click here to see the details.

Camera

1. Do I need to set a new custom white balance when I change my exposure?

  If you are photographing in AMBIENT  light, then you do not need to reset your custom white balance when you change your exposure.  The reason for this is that ambient light is constant, and when you set a custom white balance you effectively calibrate your camera to the color temperature of ambient (constant) light falling on a subject.  The color temperature remains constant, regardless of your exposure.  Therefore, Aperture, Shutter, or Program modes will automatically set a good exposure while setting a custom white balance in ambient light.

If you are using STROBES, then it becomes necessary to reset the custom white balance when you change your exposure.  A difference in exposures between that used to custom white balance a camera, and the exposure used to photograph a subject MAY yield an incorrect result.

As a rule of thumb, this would only happen when exposures slower than 1/125 of a second are used for either the custom white balance, or the subsequent shot of a subject.  The reason for this is that exposures slower than 1/125 of a second begin to be influenced by the ambient light present in the shooting environment.  The slower the exposure, the greater the influence the ambient light has on the resulting color of the image.  Therefore, changing the exposure when shooting slower than 1/125 of a second changes the ratio of ambient light to artificial light, and this in turn changes the overall, average color temperature recorded in the custom white balance procedure.

For this reason, when shooting using strobes, we recommend using the same manual exposure for your custom white balance that you will use for taking the photograph.

2. Will the ExpoDisc work with my camera?

  If your digital camera allows you to set and save a custom white balance, then you can use the ExpoDisc. It also has a variety of film camera uses (see the ExpoDisc Film Instructions) the most useful of which is taking a "gray frame" shot at the beginning of a roll of film that your lab can later use to establish the correct color correction for your images.

3. How does an ExpoDisc differ from a gray card?

  Gray cards are generally made out of non-durable mat board to reduce unwanted reflections but overtime they become damaged, dirty and their dyes can shift in color. As a result most gray card manufacturers recommend that the card be replaced after a couple of months of use. To use a gray card effectively it needs to occupy at least 15% of the image frame when setting exposure or color balance. Therefore, in many cases the card needs to be large (e.g. 8" x 10") which makes it difficult to carry around and store. Finally gray cards need to be used at precise angles to make sure that the light being reflected towards the camera is at the same angle as the light being reflected by the subject.

The ExpoDisc, on the other hand, is much better constructed and convenient to use: it is made of durable materials that will last for years; small enough to fit in your shirt pocket or store with your other filters; and, easier to use since it

efficiently captures and averages light from a wide angle in front of the camera which makes it less susceptible to unwanted reflections and precise positioning requirements.

4. Why do I need to switch my focus to manual to set a custom white balance?

  When in the auto-focus mode some cameras do not allow the shutter to be tripped if the camera cannot focus on a subject. The focusing mechanisms in most cameras rely on differences in contrast to determine the correct focal point. When the ExpoDisc is on the camera's lens the image the camera sees is very diffused and flat (similar to a gray card) and the camera cannot establish a focus. Setting the camera's focus to manual will allow the shutter to be tripped and a picture to be taken in order to set the white balance. After setting the white balance you can return to the auto-focus mode if you so desire.

5. Does it matter which exposure mode I use when setting a custom white balance?

  You can set a custom white balance in any of the Manual, Shutter Priority, Aperture Priority, or Program modes on most digital camereas.  You cannot set a custom white balance on any of the pre-programmed modes, including full auto program mode.

6. What white balance setting do I use when I take my custom white balance reading?

  If your camera requires capturing and saving an image to set an in-camera custom white balance, e.g. Canon, then it is recommended that you use the AWB setting. If your camera does not require capturing an image to set an in-camera custom white balance, e.g. Nikon, then this is not an issue because the camera can only be placed in the 'PRE' white balance setting for the procedure.

If you wish to avoid the in-camera custom white balance, for either Canon or Nikon, and prefer to click balance the images later in image editing software, then it is recommended that you select the custom white balance preset that most closely resembles the lighting under which you are photographing, e.g., Sun, Shade, Tungsten, etc.  The custom white balance capture and all other images taken under that same lighting should be taken using a single, constant white balance setting. This will ensure consistency when you download and begin the color correction process later.

7. Do I need to save the custom white balance reference image?

  If your camera requires capturing and saving an image to set an in-camera custom white balance, e.g. Canon, then you only need to select the ExpoDisc reference image in the custom white balance procedure to import the relevant data into your camera's memory.  You do not need to save the ExpoDisc gray frame reference image once the custom white balance procedure is completed.  Your camera will save and use this information until you replace it by setting another custom white balance. 

You may change memory cards, or delete the reference photo without losing your custom white balance settings.  However, you may wish to save these images as they may be useful as markers to indicate changes in lighting, or as reference gray frames for your post production workflow.

If your camera does not require capturing an image to set an in-camera custom white balance, e.g. Nikon, then this is not an issue because the camera does not capture and save an image.  Note. If you are post processing your color by click balancing in image editing software, then you must save the custom white balance reference image.

8. When trying to set a custom white balance my camera keeps giving me the "no good" error message. What am I doing wrong?

  You may get a "no good" message if the exposure is incorrect. Some digital cameras will reject the custom white balance reference image if it is severely overexposed, or underexposed.  Please refer to the setting a manual exposure FAQ for more details.

9. When trying to set a custom white balance my camera keeps giving me the "out of range", "over", or "under" error messages. What am I doing wrong?

  You may not be doing anything wrong. The problem may be poor color saturation. Digital cameras, for the most part, can establish a correct white balance when the source light is in the range of 2800 to 9500 degrees Kelvin. Your camera may not be able to set a white balance if the color of the source light is outside of this range. For example, there is a significant absence of red light just after sunset on a cloudless evening - the color of the source light may be outside the camera's range, and therefore the camera's ability to correct. In order to set a correct white balance the gain in the camera's red channel would need to be increased to its maximum or beyond. This situation may make setting a correct white balance impossible. When this condition occurs some cameras may display a warning message such as "no good," "over," "under" or "out of range." In certain cases the camera will default to setting the white balance to its minimum or maximum value which may be insufficient to adequately balance the color in the image and result in a color cast in your

pictures.

10. Why won't the 4x4 ExpoDisc fit into my Lee Filter holder?

  The foundation kit is at the centre of the Lee Filter holder system and is primarily designed to take standard 100mm square filters, although other filter sizes can be adapted to fit. The unit is supplied in component form to allow the photographer to construct a filter holder tailored to his or her individual needs.

This kit contains all the components necessary to construct a versatile holder, capable of holding up to four filters. The photographer can then choose which combinations of filter thickness they want to use by selecting and fitting the appropriate filter guides with the screwdriver provided. The ExpoDisc requires the installation of a 4mm filter guide into the Lee Filter foundation kit. Additional guides and screws can be purchased separately from Lee Filters.

Lighting

1. Do my manual exposure settings (shutter speed and aperture) matter when taking a custom white balance while using strobes?

  If photographing with strobes, then a difference in exposures between that used to custom white balance a camera, and the exposure used to photograph a subject MAY yield an incorrect result.

As a rule of thumb, this would only happen when exposures slower than 1/125 of a second are used for either the custom white balance, or the subsequent shot of a subject.  The reason for this is that exposures slower than 1/125 of a second begin to be influenced by the ambient light present in the shooting environment.  The slower the exposure, the greater the influence the ambient light has on the resulting color of the image.  Therefore, changing the exposure when shooting slower than 1/125 of a second changes the ratio of ambient light to artificial light, and this in turn changes the overall, average color temperature recorded in the custom white balance procedure.

For this reason, when shooting using strobes, we recommend using the same manual exposure for your custom white balance that you will use for taking the photograph.

2. How do I use the ExpoDisc with a flash unit?

  Removable flash units, or bounce (reflected) flash will provide the best results when used in conjunction with the ExpoDisc.

With removable flash units, position or place the flash at your intended shooting position, then from subject position aim the camera back towards shooting position for your custom white balance capture. Fire the flash unit remotely while taking your custom white balance capture.

When using bounce flash, aim the camera and flash towards the bounce surface (e.g., ceiling) for your custom white balance capture. Reflecting the flash off a neutral surface (e.g., silver backed mirror) will yield an acceptable white balance. Non-neutral surfaces may introduce a colorcast if used to reflect a flash for the purpose of setting a custom white balance.

Avoid aiming the camera and flash towards the subject for the custom white balance capture, especially if the subject is backlit. Aiming the flash towards the subject may produce an acceptable result only if you are photographing in an ambient lighting environment similar to the color temperature of your flash, e.g. daylight. However, you may see an inconsistent result shooting in other lighting conditions.

3. My pictures have a blue colorcast after setting a custom white balance. What did I do wrong?

  Pictures with a blue colorcast usually result from improperly aiming the camera towards a warmer light when capturing the custom white balance, than the light that is actually illuminating the subject.  Warm lights may include tungsten, halogen, fluorescent, or early morning, and late afternoon sunlight.

Photographing with on-camera flash under warm ambient light may result in bluish tinted images when the ExpoDisc is exposed to the warm light during the custom white balance capture. Follow the procedures outlined in the 'How do I use the ExpoDisc with a flash unit' FAQ for more information.

4. How do I set the white balance when the subject has his/her back to the sun?

  The best results are obtained by standing near your subject and pointing the camera, with the ExpoDisc on the lens, back to where the camera will be positioned when you actually take a picture. By utilizing this method you will be balancing to the color of the light that is illuminating the subject, not the backlight. This method also works well when the subject is in the shade or near a brightly colored, reflective surface.

Note: When taking pictures of backlit subjects it is a good idea to actually walk up to and take an exposure reading of your subject using an incident light meter or the reflective meter in your camera. As an alternative using the center weighted or spot metering functions of your camera can accomplish the same results. This will reduce the possibility of metering the backlight which could possibly result in under exposure of your subject.

5. How do I set a white balance in mixed lighting situations?

  When different light sources are mixed in the same scene, the results can be difficult to predict. It will not be possible for your camera to balance to the different color temperatures of all of the light sources at the same time. Therefore it is important to determine the predominant light source illuminating the subject and balance to it.

If the kinds of illumination in the scene are about equal in intensity and distribution, stand near the subject and point your camera back towards where you will be when taking the picture in order to set the white balance. If you want warm looking pictures, balance more towards the daylight or cool sources of illumination; if you prefer colder looking pictures, balance more towards the artificial or warm light sources. For example, the combination of tungsten and daylight illumination looks best when you balance towards the daylight.

Note: Setting a white balance with sodium or mercury vapor lights is unpredictable because such lights have a discontinuous color spectrum (i.e. they do not contain all the red, green and blue primary colors). Without a continuous spectrum in the source light your camera may not be able to compensate for the missing colors. Multi-vapor lights, similar to those used in sports stadiums, are more nearly color corrected and can be relied on.

Video

1. Does the ExpoDisc work with digital video cameras?

  Yes. White balance principles are the same for both digital video and digital SLR cameras. In fact the ExpoDisc will work with any digital camera that has the capability to set a custom white balance. This includes digital SLR's, point and shoot, and prosumer fixed lens cameras. If there is no specific size of ExpoDisc for your lens you can buy a slightly larger size and hold it in front of the lens, making sure it is tight up against the lens barrel so that there are no light leaks.

Underwater

1. Can the ExpoDisc be used for underwater photography?

  Use of the ExpoDisc underwater is not recommended. The properties of light underwater are significantly different than light in the Earth's atmosphere. Major factors influencing light underwater are: the attenuation of light as depth increases; the scattering of light from suspended particles; and, most importantly, reduced color saturation. At a depth of just 20 feet (6 meters) almost all red light has been filtered out by the water. Without special lights, underwater photography using natural light is only possible in very clear water at shallow depths of just a few feet. The ExpoDisc was not designed to address these issues.

CAUTION: The dyes in the special filters used to manufacture the ExpoDisc could be affected by immersion in water or other liquids. Salt water, in particular, is very caustic and could severely damage the ExpoDisc. The ExpoDisc Limited Warranty is void if the filter has been immersed in liquids.