400D - Av Mode - Camera adjusting iso mode

PixelTrawler

Hi

A few times lately I've noticed when using the Canon 400D on Av mode that in a sequence of photos, as well as adjusting the shutter speed as it should, I've found three times lately that its also brought the iso speed from 100 where I had it set, to 1600

I thought I did it by accident myself the first time I noticed but I was out today and when I went back through a set of images I had taken.

I stopped the car at one point and took seven photos. I noticed on the 5th photo the iso had jumped to 1600 and as you can image the quality of the photos were awful at such a high iso.

This was outside during daylight. I've gone through the custom functions and I cant see anything there.

Does anyone know why this is happening - Av mode is very useful but this is a nasty side effect. I have not noticed this in M mode but Av is so much easier when out and about.

Its a pain if I keep having to check it hasnt changed the iso.

If its the camera idoing it by design, I'd rather it slowed the shutter instead of raising the iso.

Anyone else notice and/or solve this issue or is my camera acting strange.

Edit: One other thing I've though of, I've only noticed this with my Sigma 18-200 lens but not with the canon kit lens - could be coincidence...

Paulw

You must have the camera in auto-ISO mode. Simply set the ISO to 100 or 200 yourself, and then the camera won't adjust it.

There may also be a custom function for "safety shift" I think it's called, where it does very similar.

Anyway, first make sure that auto-ISO isn't enabled.

PixelTrawler

Hi Paul

The thing is because I was concious of it happening twice before I manually set it to ISO 100 hoping it wouldnt then change it.

It happened 4 shots later. I cant see an option to do with Auto - ISO but it has to be an option somewhere.

The sigma lens is not the fastest lens in the world so it has difficulties in low light anyway, perhaps this is related but id like to understand why its happening and more importantly how to stop it.

I have the batteries out charging at the moment but I'll check through the custom functions again later.

Thanks for the advice

Redisle

Hi,
I just checked the Cn. Functions on my 400d and there isn't any auto iso function.. I also just took a few shots in burst mode Using Av and it didn't change the iso itself, it stayed at 100 where I set it..
I don't think this is something thats sposed to happen..

Paulw

After checking, I don't think there is auto-ISO on the 400D.

If you don't use the custom functions, or are not sure, then it is simple enough to just hit the option to clear all custom functions. Then take a few shots.

Hopefully it's something that simple.

challengemaster

it was doing the right thing tbh, 1600 iso = noisy as fcuk!

I've never had mine do that, mind

PixelTrawler

Hmm... this is weird then...

To change from ISO 100 to 1600 you need it hit the iso button and then move the cursor to adjust it to 1600

Not exactly something you can do in one button press by accident.

I have the camera about 5 months or so and its only in the last 2 weeks I have noticed this.

Hope its not developing a fault...

I ran through the shots again and they were taken in about 2-3 minutes and on the 5th the iso changed to 1600 - I must check for firmware updates next...

whyulittle

Another possibility but probably as unlikely, but you didn't switch to a different mode altogether by accident?

PixelTrawler

No I had it kept on Av.

I know some point and shots try to do "Image Stabilisation" in software by boosting the iso in low light but I dont think the 400d does anything like this.

But thats what the behaviour is like.

I should also mention on all three occasions it was in dull light - today was dull and overcast. Its like the camera is trying compensate...

EDIT. Last edit of the night. Googled around, cant find anything.

Paulw, I took your advice, went into the camera menu and cleared all camera settings and custom functions.
I'll try it out tomorrow and keep an eye on it

thanks to all

PixelTrawler

Well I took the camera out for a few hours today. I reset all functions and settings, used the kit lens and a combination of Av and M modes.

Twice again the camera jumped to iso 1600 and it happened it both modes.

I've taken about 2000 shots with the camera and its only in the last few weeks I've noticed this. I guess I'll have to get on to Canon next because it doesnt seem normal.

I caught it happening today. I was focusing on some mountains and was looking through the viewfinder when the shutter speed suddenly went from 1/250 to 1/2500 and it was because the camera had changed the ISO.

Its very frustrating as at the moment it means I have to keep checking with every shot. I think something has gone a bit screwy with it...

Zillah

Thats Canon for you. I hear they build them out of beer bottles and atari 64s.

kensutz

Zillah wrote: »

Thats Canon for you. I hear they build them out of beer bottles and atari 64s.

You mean Commodore 64?