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SL2 high ISO




First time posting here and new to DSLRs. A while back I bought a Canon T6 but a few days ago I saw an SL2 and decided to buy it. So I have both cameras but I'll be selling the T6. When I have both cameras on and pointed at the same spot, I notice that the SL2's ISO is always higher than that of the T6. Like the T6 is 1600 but the SL2 would be at 3200 or even 6400. Or if the T6 is 800 the SL2 would be at 1600 or 3200. This is in Auto mode on both. So, why is the SL2's ISO so high compared to the T6's even though there's plenty of light even for the T6 to only use 800 ISO for example, knowing that the SL2 should handle better in less than optimal brightness ?


The SL is like brand new and only a few months old (I have the receipt). I've done a "reset" but nothing's changed.




As ebiggs pointed out, until the metering is activated any change in the displayed Auto ISO reading would seem meaningless. Though I'm not familiar with either of these two cameras, it makes me wonder if they do make some kind of a "pre-evaluation" of the lighting under certain shooting conditions.


The newer the camera, sensor and processor, the more amazing they are at handling noise when shooting under low light and high ISO conditions. And doing a little careful editing of a RAW image file will fix most problems.


My main camera is a 60D that I bought new to make a big step up from my Canon G5 several years ago. The G5 was nearly unusable at ISO 400 and higher. The 60D blew me away at 400, 800, and 1600 with its lack of noise. Coming from the G5 and years of shooting film, it took me some time to convince myself to push it to 3200 and 6400 and usually still get acceptably low noise levels.


I can imagine a noticeable improvement in this area between the T6 and the SL2. As far as noise concerns in general, you may be making things worse for yourself if you're "pixel peeping" and just looking for a problem until you find one. If you view an image at 100% on your monitor at 18" or further away and don't see obvious problems you should be good to go. Even if there are slight traces of noise at 100% you'll likely never see them in a print.


View solution in original post



Are you using the exact same lens on both cameras? 



Mike Sowsun

Thanks for the reply, Mike.


I am using the 18-55 lens on both. I have even tried the 50mm on both and still the SL is showing double or or more the ISO of the T6. Just now tried again and the T6 was showing 800-1600 while the LS was showing 1600, 3200 or even 6400 while using the 50mm pointing exactly at the same spot and both zoomed out. I don't think that's right.

Try using Manual mode with Auto ISO with the same aperture and shutter speed in both cameras. The ISO should be very close then.


Full Auto may just have different parameters for each camera. The SL2 would have better high ISO performance so it will probably default to a higher ISO to improve overall image quality. 


The difference between 800 ISO and 3200 ISO is only 2 stops. It is like going from 1/30 shutter speed to 1/120.

Mike Sowsun

Assuming that the shutter speed is twice as fast for the SL2 it could be that the algorithm figures that you have better iso performance with the SL2 and allows for higher ISO's.

Check your metering mode. You can get a wide difference when using Spot Metering compared to the default Evaluative Metering mode.
"The right mouse button is your friend."


" I notice that the SL2's ISO is always higher than that of the T6."


ISO is only one part of exposure.  What are the other two?  SS and aperture?  And, you are  using the exact same lens, not just one that has the same FL?  Exactly the same?


The Rebel SL2 has a more advanced image processing engine, the DIGIC 7, the T6 has a DIGIC 4.  It, the SL2, is supposed to have better high ISO and better color rendition.

EOS 1DX and 1D Mk IV and less lenses then before!


Thank you all for taking the time to reply.


Tried the suggestion by Mike. Manual mode with Auto ISO and same SS and Aperture setting on both. The T6's ISO was constant 1600 without pressing the shutter button but once pressed half way it went down to 800. The SL was jumping from 1600 all the way up to 6400 but settled at either 800 or 1600 most of the times when pointed exactly at the same spot as the T6.


Tried switching the 18-55 lens between the two cameras but same results. But like I mentioned even with the 50mm lens the SL was still using higher ISO numbers in Auto compared to the T6.


Now, I know maybe this is how the SL2 is designed to function but I know the SL2 is better than the T6 when it comes to dark/er scenes and I'm no expert but shouldn't that mean the camera should use lower ISO numbers (in Auto) espeically that it has a better sensor ? I don't know the answer but that's what I assumed ( better sensor = less need for the camera to bump up the ISO numbers).


And I don't understand this, I know higer ISO = more grain in photos. So, how come the SL is using way higher ISO numbers (in Auto) ? Wouldn't that mean grainier photos than the T6's ?? My understanding is that all ISO settings are similar in all cameras. I mean like an ISO of say 1600 in camera X should produce similar noise to that of camera Y if it too is at 1600.  Yes I know sensors matter.


Have you tried resetting the camera(s)?  There are settings that can cause the differences.  Of course, there always could be something different with your camera.  But, try resetting the camera back to factory defaults.

"The right mouse button is your friend."

Similar ISO does not produce similar digital noise (grain) in different camera types. Sensor Technology and a Digital processing power has increased dramatically over the last 10-15 years.  Each year seems to bring improvements.


Yes, the SL2 has a better sensor and it will have less noise at higher ISO.  ISO 1600 on the T6 will be comparable to ISO 3200 on the SL2.

Mike Sowsun