My cheap variable ND Filter

[MikeandReneePlus5]

So some may recall from another thread I took the plunge on a $15.55 variable ND filter.

Here are some test shots. Let me know what you think.

Question: The meter was dead on for each shot. why do they get darker? Is that because it's a cheap filter?

Also, the filter doesn't have traditional stop settings, but rather a marked dial with 11 settings, one min, one max (which is basically black) and 9 in between. These are straight out of the camera. All at ISO 100

No filter, 1/800 f/2.8

Cheap ND filter, one step above min, 1/250 f2.8

Cheap ND filter, mid point of dial, 1/100 f2.8

Cheap ND filter, one step below max, 1/8 f/2.8

 

[photo_chick]

A neutral density filter is like sunglasses for your camera. Its purpose is to cut the amount of light entering so that you can either use a larger aperture, a slower shutter speed or a combination of the two in a given situation. It sounds like it was acting as it is supposed to with the normal variations you get unless you manually keep things the same, shifting the exposure value accordingly.

 

[MikeandReneePlus5]

Yes I know that....

that's why the shutter speed changed...

I locked the ISO at 100 and the f-stop at 2.8 so the camera should read the light with the various NDs and give a shutter speed...and shouldn't that resulting exposure be identical?

 

[boBQuincy]

Yes I know that....

that's why the shutter speed changed...

I locked the ISO at 100 and the f-stop at 2.8 so the camera should read the light with the various NDs and give a shutter speed...and shouldn't that resulting exposure be identical?

Yes, the exposures should be identical. Afaik most (all ?) variable ND filters are no more than two stacked polarizers. Maybe the dual polarizers are playing games with the meter, maybe one (or both) is a linear polarizer ?

 

[photo_chick]

If you're letting the meter do it all it's not a controlled situation. The light coming into the lens changes and the meter isn't that smart, at least mine isn't. I have the same thing when I use a variable ND filter if I leave the settings up to the meter. But if I shoot those in manual mode and adjust the exposure value the appropriate number of stops it looks the same. If you are shooting in manual and they're different then you're probably just not hitting the right number of stops for that particular filter.

 

[kgreen]

My 0.9 ND filter should be here friday! Gives me just enough time to play around a bit, before the local firework displays the end of this month. I can't wait!

 

[mom2rtk]

I think I just need a different fireworks display to attend. I tried using my ND filter to get more bursts last July 4th, and it just looked like a mess. Too many bursts all in the same spot I think. Why can't they all be like Disney?

 

[cpbjgc]

I was wondering what metering mode you are using? I think that would have an impact of the darkness of the background (your subject does not look much darker in the ND shots). If you use evaluative metering you may get a different shutter than using center-weighted or spot.

A cheaper filter can also result in more vignetting, which I think is happening with your shots.

Have fun with your filter!

 

[Experiment_626]

I think I just need a different fireworks display to attend. I tried using my ND filter to get more bursts last July 4th, and it just looked like a mess. Too many bursts all in the same spot I think. Why can't they all be like Disney?

I had exactly the same problem last July 4; very boring result.

SSB

 

[WDWFigment]

I'd never rely on the camera's meter when using a neutral density filter.

 

[eblong]

Your pictures all came out basically the same because you allowed the shutter speed to vary, and you were dealing with static objects.

A ND filter can be used to either:

• Allow altering the aperture for static subjects, thereby allowing more open apertures and therefore a shallower Depth of Field on bright days as less light enters.
• Allow slower shutter speeds to capture the effects of movement (waterfalls, rivers, cars, or anything else moving) while keeping the aperture the same.

Changing shutter speeds with static objects like you did is kind of a no-op, but you already know that. If all you are after is to darken the image captured, go to manual and start increasing the amount of under exposure.

 

[MikeandReneePlus5]

The metering was indeed evaluative.

Really the slight exposure differences are not a big deal...I wasn't trying to get them identical ....otherwise I see now I would have to go to manual and adjust stops the right way....i was just using a few different settings on the filter.

I was just wondering if anyone could tell anything wrong with this cheap-o filter as compared to a much more expensive one.

Possible vignetting? I'll shoot some more shots on sunny days (can't wait for the beach) throw them up here at some point in case anyone is curious like me.

More troubling to me is why that liatris stalk isn't tack sharp (even in the no filter shot, so it isn't the filter). I was on a tripod, no breeze (and 1/800 anyway so it shouldn't matter) . Canon T2i with the 17-55mm @ 2.8. I feel the image should be sharper.

 

[mom2rtk]

I think one of the points in buying higher quality (i.e. more expensive) filters is that you don't want to put a $15 piece of glass in front of the expensive glass of your lens. Loss of sharpness is what I'd expect to see with an inexpensive filter.

 

[photo_chick]

More troubling to me is why that liatris stalk isn't tack sharp (even in the no filter shot, so it isn't the filter). I was on a tripod, no breeze (and 1/800 anyway so it shouldn't matter) . Canon T2i with the 17-55mm @ 2.8. I feel the image should be sharper.

It's not sharp because it's a $15 filter. Also, not sure of your focusing method but some AF systems don't like to focus through ND filters.

 

[MikeandReneePlus5]

I think one of the points in buying higher quality (i.e. more expensive) filters is that you don't want to put a $15 piece of glass in front of the expensive glass of your lens. Loss of sharpness is what I'd expect to see with an inexpensive filter.

It's not sharp because it's a $15 filter. Also, not sure of your focusing method but some AF systems don't like to focus through ND filters.

the first one, without any filter, isn't sharp either. I used AI one-shot, center AF point selected.

I know you guys can't solve that problem just sayin...it ain't the filter.

I may need to enter the dreaded world of lens/camera calibration.

 

[photo_chick]

Check where you're focusing. Looks like it's more on the stalk to the left, not the center one. It's sharp there, and perhaps a bit over sharpened in processing.

 

[boBQuincy]

Maybe try live view focus to see if that makes a difference.

 

[cpbjgc]

On the focus, I agree with what Danielle and Bob said above - stalk to the left does look a bit sharper.

I like shooting with ND filters (not variable) and I find much better results using live view and manually focussing. I tend to use spot metering when not in live view, and it can give wonky results for the exposure when using ND filters.

Again, have fun experimenting!

 

[MarkBarbieri]

Metering should work just fine with ND filters with one precaution. You need to make sure that the viewfinder is covered. If you don't cover the viewfinder, light will leak in through it and cause the camera to see more light than is really there. It isn't a problem without an ND filter because so little light gets in that way relative to the light coming in through the lens. You have the problem when you put a really dark filter on the lens.

If you are metering with your eye pressed up to the viewfinder, this isn't a problem. When you've got the camera on a tripod and you are metering with your eye away from the viewfinder, you'lll see the problem. Some cameras come with a viewfinder cover built into the camera strap or even built into viewfinder itself. If you don't have either, just cover the viewfinder with your eye or finger when you are metering with a dark filter on your lens.