Help IR

[Drudkh]

HELP!!! HELP!!!!



see the corners and the middle.

[gooseberry]

Hey mate,

From the squarish nature of the hotspots, looks like reflection of the light off your sensor into the lens and back again.

[IRman]

Originally Posted by Drudkh HELP!!! HELP!!!! see the corners and the middle.

Is this just one picture happened like that or all the pictures?

This could be the light leak thru the side of your IR filter or reflection from the opaque IR filter of the things behind you. If you hold the filter by hand, try to make sure it is tightly sit on the edge of the lens barrel.

Good luck

[Drudkh]

I was shooting with a Zenitar 16mm fisheye. the filter was cut circular to fit into the rear filter. It was tight and happenes to all. I tried to open wide at f/2.8, ISO1600 and still gets a minimal of such effect.

If its because of the reflection from sensor and back, what should I do?

Oh, I forgot to mention I was given a small piece of Kodak Wratten No 87 from Nisa.

[Drudkh]

I just tried with the filter outside, hold by blutack, still no go.

[Drudkh]

I think the sensor could be too reflective or at least the IR pass filter on front of the CCD?

[gooseberry]

Originally Posted by Drudkh If its because of the reflection from sensor and back, what should I do?

Unfortunately, not much you can do short of changing the lens. As you know digital sensors are a lot more reflective than film, and with some lenses you can get the problem of internal reflection off the sensor and back again - that's why for example some manufacturers are re-doing some of their lenses with special coatings to reduce the internal reflection. (eg Tamron Di).

Also your rear IR filter could be the main one causing the reflection back.

But it seems the D7D has a lot more reflection off the sensor in the corners than other cameras I've seen, most tend to have hotspots in the middle with certain lenses.

[Drudkh]

Originally Posted by gooseberry Unfortunately, not much you can do short of changing the lens. As you know digital sensors are a lot more reflective than film, and with some lenses you can get the problem of internal reflection off the sensor and back again - that's why for example some manufacturers are re-doing some of their lenses with special coatings to reduce the internal reflection. (eg Tamron Di). Also your rear IR filter could be the main one causing the reflection back. But it seems the D7D has a lot more reflection off the sensor in the corners than other cameras I've seen, most tend to have hotspots in the middle with certain lenses.

Lets say, if there's no way to get rid of this reflective light, is there a way in post-processing to remove them?

[gooseberry]

Thinking about it, I definitely believe it's the rear IR filter causing the refection back (at least most of it). You've got a highly reflective sensor, and right in front of it you have a dark FLAT surface bouncing any reflection straight back to the sensor. If the filter wasn't so flat, you would probably not have as much of a problem.

As for post-processing for removing - not sure of the techniques, will leave it up to the PS experts.

[IRman]

Originally Posted by Drudkh Lets say, if there's no way to get rid of this reflective light, is there a way in post-processing to remove them?

Another option is to cut the 87 filter and paste directly to the hot mirror of the sensor, however this need to be done in extreme be careful. Maybe this method would help.

[Drudkh]

Originally Posted by gooseberry Thinking about it, I definitely believe it's the rear IR filter causing the refection back (at least most of it). You've got a highly reflective sensor, and right in front of it you have a dark FLAT surface bouncing any reflection straight back to the sensor. If the filter wasn't so flat, you would probably not have as much of a problem. As for post-processing for removing - not sure of the techniques, will leave it up to the PS experts.

Thanks for all the help, pal. I'll try and see if I can do something to make the filter curve up or something to see if there's any difference.

Cheers!

[Drudkh]

Originally Posted by IRman Another option is to cut the 87 filter and paste directly to the hot mirror of the sensor, however this need to be done in extreme be careful. Maybe this method would help.

Do you mean like what Max 2.8 did to his cam? Paste the IR filter right in the face of the CCD? If this works, I have no more filter liao.
This piece was given by Nisa. Alamak, this didn't work, how to answer her?

[IRman]

Yes, I did it before and its fine. Just need a small piece, not sure CP still have the LEE filter or not, you could buy 75 x 75 mm and try it, rather than keep spend time in PS for removing it.

[Nisa]

Originally Posted by Drudkh Do you mean like what Max 2.8 did to his cam? Paste the IR filter right in the face of the CCD? If this works, I have no more filter liao. This piece was given by Nisa. Alamak, this didn't work, how to answer her?

don't worry
need another piece?

[Drudkh]

Hi gooseberry,

guess making the filter curve didn't work.

[Drudkh]

Originally Posted by Nisa don't worry need another piece?

I don't dare liao, unless I am sure the next attempt will work (get rid of the reflective problem). THANK YOU for cutting up your precious for me.

[Nisa]

Originally Posted by Drudkh I don't dare liao, unless I am sure the next attempt will work (get rid of the reflective problem). THANK YOU for cutting up your precious for me.

no worries. your experiement will help others when they need such help.

[Drudkh]

Anyway, does anyone see my sample photos (special effects) as an art? apart from the normal IR you always see.

[teerex]

Originally Posted by Drudkh Anyway, does anyone see my sample photos (special effects) as an art? apart from the normal IR you always see.

Ya, saw your photo.

I'm no PS expert, but worst case, try using the healing brush should help to rid the "special effects".

[gooseberry]

Originally Posted by Drudkh Hi gooseberry, guess making the filter curve didn't work.

Yeah, seems to have made the corners slightly worse. With that little bit of curve, there's still chance for it to reflect back. Is it possible to have the filter flat, but at a slanted angle so if there is any reflection, most of it is away from the sensor ? Not sure you'd be able to do this.