# Long Exposure Problem - severe red tint



## ontarioguy (Oct 22, 2015)

So I'm new to long exposure, this is my problem:
I took a couple photos today with my new ND 3.0 filter, and they all have this major red tint over the entire photo (see photo examples).
I don't know why this is happening because I've used this filter previously and there was no red tint in the resulting long exposure photos.

My settings used to take these shots (Nikon D7100):
*bulb mode
*fstop: 9
*ISO 125
*exposure time: 45 seconds for first photo and 1 minute for second photo

What am I doing wrong?


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## ontarioguy (Oct 22, 2015)

This is what the colors look like in a regular photo, same spot, same day.


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## DB_Cro (Oct 23, 2015)

Red ND?


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## 480sparky (Oct 23, 2015)

Are you covering the viewfinder during exposure?


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## astroNikon (Oct 23, 2015)

In the old days, and the better cameras (d700, d750 and above) they have a switch to close the viewfinder.
Otherwise the light comes in the viewfinder, through the prism and down into the sensor area to give a cast like you have. 

Here's a more extreme example of not covering the viewfinder
Manual exposure, 6 sec, f/5.6, ISO 400


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## 480sparky (Oct 23, 2015)




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## ontarioguy (Oct 23, 2015)

480sparky said:


> Are you covering the viewfinder during exposure?





astroNikon said:


> In the old days, and the better cameras (d700, d750 and above) they have a switch to close the viewfinder.
> Otherwise the light comes in the viewfinder, through the prism and down into the sensor area to give a cast like you have.
> 
> Here's a more extreme example of not covering the viewfinder
> Manual exposure, 6 sec, f/5.6, ISO 400



I was using my thumb to cover the view finder. It might be possible that it let red light through, similar to how when you put your thumb over a flashlight bulb it turns red.
Thank you very much!


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## astroNikon (Oct 23, 2015)

if anything, use the camera strap and place it over the viewfinder.
but be careful with your finger as you may ever so slightly jiggle the camera and induce movement blur or jumps.


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## 480sparky (Oct 23, 2015)

I use a lens cap.


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## astroNikon (Oct 23, 2015)

480sparky said:


> I use a lens cap.


over your lens ?

I have a 3rd party eyecup so I started using my camera strap but I just made my own cover.


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## Braineack (Oct 23, 2015)

I like the colors compared to the snapshot.


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## 480sparky (Oct 23, 2015)

astroNikon said:


> 480sparky said:
> 
> 
> > I use a lens cap.
> ...



Over the VF, silly!


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## astroNikon (Oct 23, 2015)

480sparky said:


> astroNikon said:
> 
> 
> > 480sparky said:
> ...


oh, the back lens cap.   I was thinking the front lens cap ... couldn't figure out how you got it to stay on.  LOL


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## ontarioguy (Oct 23, 2015)

480sparky said:


> astroNikon said:
> 
> 
> > 480sparky said:
> ...



Maybe he thought you wanted a detailed long exposure shot of the back of your lens cap? you never know, abstract photography is a thing lol


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## 480sparky (Oct 23, 2015)

astroNikon said:


> oh, the back lens cap.   I was thinking the front lens cap ... couldn't figure out how you got it to stay on.  LOL



Silly me, I just hold it with my fingers.


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## TCampbell (Oct 23, 2015)

The ND filter (ND = "Neutral" density... emphases on "Neutral" because it's not supposed to favor any part of the visible light spectrum more than any other) are sometimes not so neutral after all.  Even the Lee "big stopper", while designed to be "neutral" suggests that each filter is unique and some may not be so neutral and may require a white balance correction.  Lee suggests owners test their Big Stopper filters.

So I'm wondering... if your filter isn't actually "neutral".

I am skeptical that it's light leaking through the back.   Once the reflex mirror swings up it usually blocks any light from the viewfinder from reaching the sensor (usually it's more of a problem with 'metering' accuracy than exposure.)

I read an article where the author was skeptical about the need to cover the viewfinder.  So they did an experiment where they left the lens cap on, wrapped the entire body EXCEPT for the viewfinder (so the only way for light to enter the camera was in the viewfinder) and then took a very long exposure with a bright light shining into the viewfinder's eyecup.  They inspected the images for signs that light had leaked in and saw... nothing.  No signs of light leakage whatsoever even after going out of their way to create a problem.  The conclusion is that modern DSLRs may do a much better job of sealing out light leaks from the viewfinder than older cameras.


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## Derrel (Oct 23, 2015)

It's worth it to actually watch this video, just to see the way Lee actually dyes its filters...with women hand-dunking filter blanks in open-topped tubs of chemical solutions, doing everything mostly "by feel", basically. This explains the reason Lee filters are so often out of stock. Lee Filters is run like a cottage business.

In the comments section on YouTube, one photographer wrote, "I just obtained a Big Stopper(my goodness finally after all the wait!!) and I love it!! Contrary to what people say about the blue cast, I actually like the effect of the blue cast on my images; in my opinion it gives it a slight boost to the blue sky in a daylight and make it look deeper."


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## ontarioguy (Oct 23, 2015)

TCampbell said:


> The ND filter (ND = "Neutral" density... emphases on "Neutral" because it's not supposed to favor any part of the visible light spectrum more than any other) are sometimes not so neutral after all.  Even the Lee "big stopper", while designed to be "neutral" suggests that each filter is unique and some may not be so neutral and may require a white balance correction.  Lee suggests owners test their Big Stopper filters.
> 
> So I'm wondering... if your filter isn't actually "neutral".
> 
> ...





Derrel said:


> It's worth it to actually watch this video, just to see the way Lee actually dyes its filters...with women hand-dunking filter blanks in open-topped tubs of chemical solutions, doing everything mostly "by feel", basically. This explains the reason Lee filters are so often out of stock. Lee Filters is run like a cottage business.
> 
> In the comments section on YouTube, one photographer wrote, "I just obtained a Big Stopper(my goodness finally after all the wait!!) and I love it!! Contrary to what people say about the blue cast, I actually like the effect of the blue cast on my images; in my opinion it gives it a slight boost to the blue sky in a daylight and make it look deeper."



So if this is a case and my ND filter isnt so neutral, how do you explain the difference between these two photos that I took, both using the same filter, both in daylight with similar settings.






OK, i understand now that the problem must be that light from the IR spectrum must be getting in causing the red tint problem (it's apparently quite common with ND filters). Apparently I need something to block this IR light as well, what can I use?


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## Derrel (Oct 24, 2015)

I am more concerned about white balance and tint settings than anything. The regular color image is shot with AUTO1 white balance setting. I think the filter's presence might have affected the white balance applied to the reddish images. Can you look at the EXIF information in the long exposure shots, and see in your software what the exact white balance and color tint settings were?


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## Buckster (Oct 24, 2015)

My Cokin NDs have a very strong magenta cast, and it seems to be stronger the longer the exposure is.  I started using B&W NDs a few years ago, and they are working much better for me in terms of keeping things neutral.

On the issue of light leak through the viewfinder, I recall having that problem once while shooting the San Francisco Bay Bridge one night from Treasure Island using a Canon 20D.  As I reviewed the shots I saw a very noticeable "ghost" of light in the images.  As I worked through isolating the problem, it turned out to be the uncovered viewfinder letting light in from the parking lot street lights that were all around behind me.  Once I covered that up, I was good to go again.


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## TCampbell (Oct 24, 2015)

ontarioguy said:


> So if this is a case and my ND filter isnt so neutral, how do you explain the difference between these two photos that I took, both using the same filter, both in daylight with similar settings.
> 
> View attachment 110323
> 
> OK, i understand now that the problem must be that light from the IR spectrum must be getting in causing the red tint problem (it's apparently quite common with ND filters). Apparently I need something to block this IR light as well, what can I use?



When I inspect the tree line at the falls, it does indeed appear "red".

The red won't be IR light -- your camera filters that out (internally).  

You could certainly test the filter by taking a photo of a plain white sheet of paper in bright sunlight to see if the "white" paper comes out with a red cast.  

Are you shooting RAW or JPEG?  If JPEG, the camera white balance might be over-warming the image.


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## KmH (Oct 24, 2015)

With DSLR many cameras Auto White Balance is a pox that needs to be eradicated.

I too am thinking it's mainly a white balance setting issue, even if AWB wasn't used.


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## Malavok (Oct 24, 2015)

It's hard to know whether or not it's a white balance issue without being able to fiddle with the RAW file. 



Buckster said:


> My Cokin NDs have a very strong magenta cast, and it seems to be stronger the longer the exposure is.  I started using B&W NDs a few years ago, and they are working much better for me in terms of keeping things neutral.
> 
> On the issue of light leak through the viewfinder, I recall having that problem once while shooting the San Francisco Bay Bridge one night from Treasure Island using a Canon 20D.  As I reviewed the shots I saw a very noticeable "ghost" of light in the images.  As I worked through isolating the problem, it turned out to be the uncovered viewfinder letting light in from the parking lot street lights that were all around behind me.  Once I covered that up, I was good to go again.



I had the same problem with Cokin filters, which is why I'll never buy them again. I've used Tiffen, Hoya, B&W with no issues. Even my dirt cheap Altura ND filters don't cause the awful purple cast that Cokin did.


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## ontarioguy (Oct 26, 2015)

Thank you for everyone who replied to this thread.
This last few days I played around with my camera, and alas my issue was indeed white balance.
I assumed it was my Tiffen Filter to blame (but I love it now that I know how to manually adjust my white balance).
The red colour-cast / tint is gone!


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