Taking photos of fish in a bucket to look at colouration changes, what do I need to consider?
Asked by
bongo (
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May 10th, 2012
So as part of my masters project I will be going into the field and catching fish. I will then be putting these fish into buckets and taking photos of them. I will then take these photos back to the lab and assess colours with imaging software (hopefully Photoshop but probably imageJ as this is free)
I will be taking these photos through the water in outside conditions with a macro lens and ring flash (however I do have another standard lens (cant remember the dimensions etc off the top of my head now but I can get hold of them if it is needed)
What do I need to consider when taking these photos so that:
1. I have minimum to no light reflectance on the surface of the water so that I take the photo through the water surface. and
2. so that colour variation between photos is not affected so that I can quantify the colour change.
I have been thinking that I might need some kind of shading or black cover to put over the whole photograph set up as to remove external light influences. Also, would a polarizing filter help with reducing/removing the surface water reflectance or would this complicate matters more with distinguishing true colours? This is very important as I do not want to have the flash or natural light reflect back into the photo to distort the light levels.
I am using a using a Canon EOS 400D digital camera, 90mm tamron sp Di 1:1 macro lens and a ring flash and will include a standardized colour chart in my photos but if I can reduce any variation in photos before I take them using a correct camera set up this will obviously take me lots of time in digitally altering colour balances. Also if I do have to digitally alter colours I am not sure of how true a representation this will have on the actual colours and so would prefer to keep this to a minimum.
Also is there anything else I will need to consider?
I will be taking another photo of each fish next to a ruler to standardise for scale with each fish so length etc can be worked out more accurately.
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15 Answers
Put a truly white card or object in the bucket for color reference.
Most photo editing programs can use that to do color correction automatically.
I did say I will be using a colour standard chart however I have been working with imageJ for a few weeks now and can not work out how to alter colours to a standard accurately I can change them but when I set them to specific specifications and remeasure the standard to check if it matches the specifications it is almost there but not quite and also each colour is out by a different amount so I can not even standardise the error. This is why I would prefer to understand how to do standardise the colours within the photo as best as possible before I take the photo.
Also how do I consider the light reflection from the surface of the water?
The polarizing filter is the perfect solution to take care of the light reflection, if the water surface is still.
I haven’t worked with ImageJ but I do know Photoshop has an eye-dropper type tool that lets you identify true white in the image and it can automatically correct all colors based on that.
The GIMP (Gnu Image Manipulation Program) also has a white balance correction section.
GIMP is also free and available for most platforms.
Ok cool thanks, I had not heard of GIMP. ImageJ does have a dropper tool but I cant work out how to alter the colours from that, it will only allow me to select an area rather than a point, I think this is why I am getting so much variation when I am changing my colours. I will try GIMP but if not it looks like I am going to have to fork out the cash for photoshop…
You need to think about the trout. It’s a fairly delicate cold water fish. 40 minutes plus in a bucket will probably be too much for the fish to survive.
Wait now I am confused, I have just done some browsing, is it definitely a polarizing filter I need or a UV filter? Or both?
@Adirondackwannabe they will have battery powered air stones in with them and undergo minimal handling and any handling will be done by professionals. We will also have a cannister of oxygen on site to infuse the water so that it is fully saturated with oxygen before we put the fish in. Water will be used from the stream we are taking the fish out of and the buckets will be partially submerged in the stream water to maintain a constant temperature.
Similar experiments have been done by these people before in the same rivers/streams with 0 mortalities.
@bongo Thank you. You obviously know how to care for them. Nice job.
Polarizer will do the trick if you are concerned with reflections from outside the bucket.
I’ve used them to photograph into a stream that would otherwise be totally obscured on the surface by reflections from above. Polarizer will also cut reflection on a window, etc.
@Adirondackwannabe animal care is always the priority when working with animals. I do this subject because I love animals. Also a happy fish gives accurate data.
@dabbler excellent, thanks! will order one now and start playing!
Polarizing filters are most effective when the photo is being taken at an angle to the reflecting surface, not directly toward it. I assume that you’ll be shooting straight down into the bucket, correct? In that case, the reflected light won’t be polarized, and the filter will screen out very little of it. Your best bet is to provide a black screen above the camera setup so that light coming from that direction is eliminated.
Another thought: the closer the lens is to the surface of the water, the less you’ll pick up the reflection of the ring flash. How close will depend on the focal length of the lens.
Always make sure the camera is in the same place, obviously. It sounds like you’re prepared enough that you will be mounting it.
Make sure the water is filled to the same exact height after you transfer the fish. If your buckets are tapered, narrower at the bottom, you could cut a rigid piece of transparent material which went just part way down and then lodged itself. This could tell you how much water to add or remove, and could also dampen waves the fish will certainly cause.
@6rant6 Yeah no worries I understand all measures required for consistency and repeatability. It really is more the photography aspect of it I am not 100% with. Methodologies are not a problem. Good idea about a method to dampen the ripples. I have plenty of silicone and so will look into attaching something within the bucket when my order arrives!
@thorninmud Yes I was thinking I might need some kind of shade or screen too. and Yes I will be taking the photos directly from above. However I have read that it is best to take photos at a 30 degree angle to reduce glare reflectance and so I may consider doing one of each. Cant hurt to have 2 photos can it, I can always discard the angled photos if they are useless.
Thanks for all your help guys this info is really useful!
Did you say what color the buckets will be? That seems pretty important to me. I’m thinking white of some kind.
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