Hot spots in Tokina 12-24mm

[dcubes]

Hi guys,

I got a tokina 12-24mm and I realised that there's hotspot when I tried to shoot IR.
Pardon my ignorance, but is there anyway to minimise that from happening?
It is very obviously when shooting IR.. if in colour, it is even worst..

Any advise?

Regards
dcubes

[Hoky]

I think there's no way to go about it.

See this thread for compatible cameras and lenses.
http://forums.clubsnap.org/showpost....57&postcount=1

[Francis247]

Originally Posted by dcubes Hi guys, I got a tokina 12-24mm and I realised that there's hotspot when I tried to shoot IR. Pardon my ignorance, but is there anyway to minimise that from happening? It is very obviously when shooting IR.. if in colour, it is even worst.. Any advise? Regards dcubes

Hi there,

Maybe you can try posting your photos and your setting for the rest to analyse.

[deadpixel]

Originally Posted by dcubes Hi guys, I got a tokina 12-24mm and I realised that there's hotspot when I tried to shoot IR. Pardon my ignorance, but is there anyway to minimise that from happening? It is very obviously when shooting IR.. if in colour, it is even worst.. Any advise? Regards dcubes

I posted a test on this about a year ago I think.

Basically, in order to avoid the hotspot, you'll have to shoot with a large aperture. Whenever you shoot from between 12-15mm, you should try to limit yourself to apertures between f/4- f/4.5. For focal lengths above 15, you can go down to f/5.6.

I know this does not give you much in terms of depth of field, but it cannot be helped. The only other solution is for you to learn to shoot in hyper focus and that is the subject matter of another thread I posted, also quite sometime back.

Cheers,
Matt

[TrailsofLife]

Originally Posted by deadpixel I posted a test on this about a year ago I think. Basically, in order to avoid the hotspot, you'll have to shoot with a large aperture. Whenever you shoot from between 12-15mm, you should try to limit yourself to apertures between f/4- f/4.5. For focal lengths above 15, you can go down to f/5.6. I know this does not give you much in terms of depth of field, but it cannot be helped. The only other solution is for you to learn to shoot in hyper focus and that is the subject matter of another thread I posted, also quite sometime back. Cheers, Matt

I remember that post, Matt. Yep, I think this lens has a hot spot problem. If possible, shoot wide open, if not dun go below f5.6. This rule of thumb applies to most lens, anyway.

[adamadam]

If you use a IR-modified camera without a filter in front of the lens - does the hotspot still occur?

[karel]

I've been thinking about changing the angle to the sun a little to the left or right .. because the hot spot is not consistent in my lens .. sometimes it's there, sometimes it's not ..

[TrailsofLife]

Originally Posted by adamadam If you use a IR-modified camera without a filter in front of the lens - does the hotspot still occur?

Hi,

I've shoot with a modded 300D at have f16-22, so far, no hotspot. But there isn't much sun lately. Also, I use Sigma 10-20mm, can't be sure if Tokina's 12-24 will be the same.

[deadpixel]

Originally Posted by adamadam If you use a IR-modified camera without a filter in front of the lens - does the hotspot still occur?

Yes it will, so long as you stop down the lens to much, the hotspot will appear.

Cheers,
Matt

[TrailsofLife]

Originally Posted by deadpixel Yes it will, so long as you stop down the lens to much, the hotspot will appear. Cheers, Matt

Matt,

You mean for Tokina only? Because so far I've been shooting at f16 or lower. You know how haywire the metering can get right? I've to use f16 or below and -2 stops on the shutter speed to get right exposures, but I have not encounter hotspots so far.

[deadpixel]

Originally Posted by Max 2.8 Matt, You mean for Tokina only? Because so far I've been shooting at f16 or lower. You know how haywire the metering can get right? I've to use f16 or below and -2 stops on the shutter speed to get right exposures, but I have not encounter hotspots so far.

Yep, hotspots are quite lens + camera specific and the quality of the aperture blades coupled with the glass (whether or not they suffer from CA) seem to play a part in determining how bad the hotspots can become.

Cheers,
Matt

[TrailsofLife]

That means D70(both unmodded and modded) with Tokina is a bad combo...

Such a waste, among the few APS-C lens, Tokina's built and quality is the best.

[photographique]

I got confused...large aperture is like 2.8, 3.5, how come f16 and above no hot spot?

[TrailsofLife]

Dun confuse.

I use a modified camera, so I can shoot at small aperture. For unmodified camera, f5.6 or wider is recommended to prevent hotspot.

[vortex]

anything above f6.3 on the sigma 10-20mm also got hotspots

[mouselim]

Pardon my ignorance, maybe i know what hot spots are but in different definition but isn't hot spots areas whereby the flash or sun "burn" portion of the image?

If so, what has this got to do with the aperture size? If Tokina 12-24mm cannot shot with a smaller aperture size (eg. f/11), what's the point of using it as most often than not, this lense will be used for landscape photography whereby large depth of field is almost essential.

Unless I am again missing the point here as this is only applicable to IR photography only?

[deadpixel]

Originally Posted by mouselim Pardon my ignorance, maybe i know what hot spots are but in different definition but isn't hot spots areas whereby the flash or sun "burn" portion of the image? If so, what has this got to do with the aperture size? If Tokina 12-24mm cannot shot with a smaller aperture size (eg. f/11), what's the point of using it as most often than not, this lense will be used for landscape photography whereby large depth of field is almost essential. Unless I am again missing the point here as this is only applicable to IR photography only?

Hotspots in IR photography refer to circular spots in the center of the photos that are much brighter or rather more red than the other parts of the photo. This has been attributed to long exposures but in many test I have carried out, I found this to be inaccurate. In these tests, Exposures of 1/800 sec @ f/8 on modified IR only cameras produced hotspots when shots of 1 sec @ f/4 on non-modified carmeras didn't.

Some sites I have visited attributed this phenomenon to diffraction, where light, stricking an edge perpendicularly gets bent at an angle. With normal light photography, this isn't really noticible until you step down the lens too much and begin to see the image quality deteriorate, but with IR photograpy diffraction quickly becomes an issue as the red band is more affected than the others. What the scientist seem to have shown is that when light passes through a small circular hole, it actually creates a circular "hotspot" of light of fading intensity in the center of the image that decreases in visibility as the hole or aperture increases in size.

This may explain why we do not experience any hotspots when our lenses are wide opened...there are no perpendicular edges for the light to pass through.

You asked about the effectiveness of the Tokina if you cannot stop it down to f/11 or more because you want the DOF? Well, learn to hyperfocus, that will solve all your DOF issues. You can shoot wide open and won't even need an object to focus on.

Cheers,
Matt