iso question

[bballboy30]

I have been playing around with my rebel and bigma iso speed. I was able to get decent pics of a moose that filled the frame @ 1600 iso. I used auto focus. But the pics I took of a fox @ 1600 iso were pretty bad. The fox was far off and I used auto focus. Is the iso speed the problem? Does it affect distant subjects image qualtity worse than closer subjects? Or, should I just have used manual focus?

Thanks.
Alex

[tim]

It makes no difference how you focus, auto or manual, so long as you focus correctly. If something's moving you should use AI servo, if your camera has that feature. If you post a sample picture we can tell you what's up. If it's grainy it probably means the exposure was a little short - you need to expose to the right with high ISOs, otherwise you will get a lot of noise.

[mikeymike]

"expose to the right" please explain ???

[tim]

Read this (http://www.luminous-landscape.com/tutorials/understanding-series/understanding-histograms.shtml). The idea is to get more data on the right side of the histogram.

[bballboy30]

Tim,

Thanks for all your help. I wish I could post a pic but a don't currently have a website to host it. My pics were just a little blurry. I had a very high shutter speed and was shooting on a beanbag. Does the distance effect the amount of noise/blur that a high iso speed gives you?

Thanks.
Alex

[robertwgross]

The idea is to get more data on the right side of the histogram.

Getting the histogram to lean more onto the right half of the scale is good, as long as it does not bump onto the right edge.

The trick, for me at least, is moving it right and then leaving just the correct amount of space to avoid the bump.

---Bob Gross---

[CyberPet]

AI Focus is a good middle ground for "one shot" focus and "AI Servo", the AI Servo kicks in when it's needed (moving subjects).

Also, I find that Noise Ninja creates clear - but noise free - images, and very sharp to boot. So if the focus is correct, even 1600 ISO shots should be good enough.

[tim]

Getting the histogram to lean more onto the right half of the scale is good, as long as it does not bump onto the right edge.

The trick, for me at least, is moving it right and then leaving just the correct amount of space to avoid the bump.

---Bob Gross---

Yeah, that article I linked to has stuff like that in it, I don't retype stuff I can link to ;)

[mvonditter]

AI Focus is a good middle ground for "one shot" focus and "AI Servo", the AI Servo kicks in when it's needed (moving subjects).

Also, I find that Noise Ninja creates clear - but noise free - images, and very sharp to boot. So if the focus is correct, even 1600 ISO shots should be good enough.

Ditto!

[robertwgross]

Does the distance effect the amount of noise/blur that a high iso speed gives you?

No.

The longer focal length will magnify camera shake for any ISO setting.

---Bob Gross---

[IainB]

I was playing around with the ISO and the 50mm1.8. This shot was taken at 1/60 F2.2 ISO 1600. No sharpening. I haven't played much with the ISO settings and would also welcome some comment on this topic.
IainB

[robertwgross]

That looks like posterization going on to ruin the image.

Were you shooting RAW or JPEG files?

Was there any color space conversion going on?

---Bob Gross---

[FlyingPete]

That looks like posterization going on to ruin the image.

Were you shooting RAW or JPEG files?

Was there any color space conversion going on?

---Bob Gross---

Never seen posterization like that straight out of the camera before, what gives?

EDIT: EXIF says sRGB, been through Photoshop though.

[IainB]

Shooting RAW, and in AdobeRGB in camera. Posterisation was evident in EOSViewer before converted to a tiff for resizing in PS. It converted to sRGB when taken to PS. Other shots (see posting about 50mm 1.8 Frustratingly soft) showed no such signs.

[FlyingPete]

Shooting RAW, and in AdobeRGB in camera. Posterisation was evident in EOSViewer before converted to a tiff for resizing in PS. It converted to sRGB when taken to PS. Other shots (see posting about 50mm 1.8 Frustratingly soft) showed no such signs.

Wierd. Have you tried another RAW converter? I had a crappy old Sony Cybershot that also did that from time to time, but from the JPG's straight out of the camera. DOne alot of work at 1600 in simular lighting and also in RAW the only difference is that I always shoot in sRGB, anyway I think colour space is chosen at the coversion stage?

Yes the 50mm f/1.8 does cause issues with sharpness, mine is sharp as a tack at f/8 though, but then that sort of defeats the reason for having f/1.8 :rolleyes:

[IainB]

I'll install the other software that came with the camera and try that. At ISO 800 there was no problem. There was a chandelier close by which produced some highlights. This could have contributed to the result at 1600.