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Full spectrum modified Canon 500D. Metering issue.

Started 9 months ago | Discussions
SpaceTinkerer New Member • Posts: 2
Full spectrum modified Canon 500D. Metering issue.

Hi all!

I just converted a Canon 500D to full-spectrum, removing all filters in front of the sensor. This is a process I have done many times without issues... until now!

The camera only takes correctly exposed photos in Manual mode. In all other modes (Auto, Auto no flash, Av, Tv etc) photos are heavily under-exposed, nearly dark.

In a way, it makes sense because, for some reason, the camera decides in a relatively dark room to use settings I would expect to see under very bright conditions (e.g. ISO 100, f/19, 1/4000 sec).

I'm not really sure if this was an issue before the conversion as this is a newly ordered camera and I only tested it in manual mode(!) when it came...

Any thoughts?

Thanks.

Chris.

Canon EOS 500D (EOS Rebel T1i / EOS Kiss X3)
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Lemming51
Lemming51 Forum Pro • Posts: 15,278
Re: Full spectrum modified Canon 500D. Metering issue.

SpaceTinkerer wrote:

Hi all!

I just converted a Canon 500D to full-spectrum, removing all filters in front of the sensor. This is a process I have done many times without issues... until now!

The camera only takes correctly exposed photos in Manual mode. In all other modes (Auto, Auto no flash, Av, Tv etc) photos are heavily under-exposed, nearly dark.

In a way, it makes sense because, for some reason, the camera decides in a relatively dark room to use settings I would expect to see under very bright conditions (e.g. ISO 100, f/19, 1/4000 sec).

I'm not really sure if this was an issue before the conversion as this is a newly ordered camera and I only tested it in manual mode(!) when it came...

Any thoughts?

Thanks.

Chris.

Hmmmm.

Auto-exposure metering sensors are in the pentamirror would be expected to be unaffected by removing the Anti-Alias and InfraRed filters covering the image sensor. Did you (or maybe the prior owner)  change the mirror or focus screen, which would affect the light directed to the exposure meter?

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OP SpaceTinkerer New Member • Posts: 2
Re: Full spectrum modified Canon 500D. Metering issue.

Lemming51 wrote:

SpaceTinkerer wrote:

Hi all!

I just converted a Canon 500D to full-spectrum, removing all filters in front of the sensor. This is a process I have done many times without issues... until now!

The camera only takes correctly exposed photos in Manual mode. In all other modes (Auto, Auto no flash, Av, Tv etc) photos are heavily under-exposed, nearly dark.

In a way, it makes sense because, for some reason, the camera decides in a relatively dark room to use settings I would expect to see under very bright conditions (e.g. ISO 100, f/19, 1/4000 sec).

I'm not really sure if this was an issue before the conversion as this is a newly ordered camera and I only tested it in manual mode(!) when it came...

Any thoughts?

Thanks.

Chris.

Hmmmm.

Auto-exposure metering sensors are in the pentamirror would be expected to be unaffected by removing the Anti-Alias and InfraRed filters covering the image sensor. Did you (or maybe the prior owner) change the mirror or focus screen, which would affect the light directed to the exposure meter?

Hi Lemming51.

The upper cover was a bit stuck so I applied force to remove it. I might have accidentally squeezed the pentamirror. I guess that I will only use the camera in Manual mode as I don't want to open the camera again. Also, Manual is the default for astrophotography anyway.

Thanks for pointing me in the right direction!

Chris.

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