expandable ISO in 50D

MissB

I was comparing the 40D and 50d side by side in an online review. I noticed that the 50D has ISO 100-3200 and "is expandable in H1 from 3200-xx,xxx and in H2 from xx,xxx-xx,xxx" can't remember what the numbers were.. but I want to know what this "expandable" means.. and what is H1 and H2?? thanks!!

kini62

H1 and H2 are pseudo ISOs of 6400 and 12,800.

Gene

MissB

kini62 wrote:

H1 and H2 are pseudo ISOs of 6400 and 12,800.

Gene

pseudo??? hmm.. then if you would.. please explain whats the point of having it id love to have more sensitivity on my camera.. I just don't understand how this works.

ziggy53

ISO 100-3200 are the "calibrated" ISO settings for the 50D. The extra ISO settings are generated (basically) by underexposing and then boosting the levels by adjusting the "gain" of the captured image. It is very similar to what you can do in post-processing an underexposed image and trying to expand the available tones back to a normal tone spread of shadow to highlight.

Just like turning up the volume to try to listen to a distant radio station in your car, there comes a time when the boost just presents too much noise to be much value.

If you really need to shoot in very low light levels your best bet is a modern full-frame dSLR, like the Canon 5D MKII or the Nikon D3 and D700 models.

Another problem with very low light levels is that autofocus systems may struggle or fail at very low light levels. A flash with AF assist is very valuable to both focus in low light and to generate enough light to allow more reasonable ISO settings. As long as the flash output is modified to suite the situation, you can produce very nice images with most any dSLR.

craig_d

MissB wrote:

pseudo??? hmm.. then if you would.. please explain whats the point of having it id love to have more sensitivity on my camera.. I just don't understand how this works.

The point is to allow Canon to brag about having it. It's basically useless. "Expanded ISO range" basically means "custom function to enable ugly pictures." I experimented with this briefly after buying my 5D Mark II and then turned it off again. You'd be better off just adjusting the exposure by +/- 1 stop while shooting raw and then playing with the tone curve.

If you want a more technically precise explanation, the "expanded" ISO values are generated in software doing more or less the same things you can do yourself with Adobe Camera Raw or any other decent raw program. ISO 50 is really just ISO 100 overexposed by one stop, with a non-linear tone curve applied when generating the JPEG image. (I was very puzzled at first why my ISO 50 raw files just looked overexposed!) The expanded ISO values at the other end of the scale are just your highest hardware ISO mode, underexposed by one or two stops, and the image amplified in software afterward.

MissB

great explainations thank you.. I like the "trying to hear a distant radio station by turning the volume way up.." analogy.. Im glad I asked.. seems way less important. I also wasn't sure if the more expensive cameras handled noise better with higher ISO's .. doesn't seem like it mades a difference.

thanks again everyone

Moogle Pepper

50D? It's 7D these days, B!

(Although those cameras are really good for its target range.)

craig_d

MissB wrote:

I also wasn't sure if the more expensive cameras handled noise better with higher ISO's .. doesn't seem like it mades a difference.

Oh, it does make a difference. The most significant difference is between full-frame and cropped models. Full-frame sensors have lower pixel densities and consequently have lower noise levels. But even within the APS-C cameras, the 7D seems to be a bit better than the 50D, and the 50D is clearly better than the Rebels.

Here's a link I've been posting a lot this week. It's The Digital Picture's not-yet-complete review of the 7D. The part you might want to look at is the set of ISO noise level comparisons near the top (the overlapping images that say "Kodak Color Control Patches"). You can hover your mouse over the controls under the images to see how much noise the 5D2, 7D, 50D, and Rebel T1i show at different ISO levels.

http://www.the-digital-picture.com/Reviews/Canon-EOS-7D-Digital-SLR-Camera-Review.aspx

TeamSpeed

craig_d wrote:

The point is to allow Canon to brag about having it. It's basically useless. "Expanded ISO range" basically means "custom function to enable ugly pictures." I experimented with this briefly after buying my 5D Mark II and then turned it off again. You'd be better off just adjusting the exposure by +/- 1 stop while shooting raw and then playing with the tone curve.

I have to disagree, these modes are useful and saves the time it would take to shoot raw and do this work yourself. When I shot a couple hundred shots at ISO 6400 at one of our HS band competitions, it was a time saver, I didn't want to process all the raws and conversions, even if I could automate the process. We needed to get the images up on the website asap. The only caveat I have to this is to shoot a whibal card and set your white balance beforehand, something I didn't do.

Here is a gallery where I shot JPG at ISO 6400 the entire evening with the 50D. I have since sold that camera and now am enjoying the improved ISO handling of the 7D.

http://teamspeed.smugmug.com/CHS-Band-2009-2010/CHS-Band-At-Bluffton