SAL35f18 LA-EA2 or SEL35f18

Started Feb 16, 2013 | Discussions thread
EinsteinsGhost Forum Pro • Posts: 11,977
Re: SAL35f18 LA-EA2 or SEL35f18

paul1508 wrote:

EinsteinsGhost wrote:

paul1508 wrote:

Kiichiro wrote:

paul1508 wrote:

Why does everyone forget the lightloss through the translucent mirror?

It will cost you about a 2/3 stop!!

The SAL ISO 3200 should look like a SEL ISO 5333...
or a SAL ISO 1600 may look like a SEL 2666...
ISO 800 like 1333 and so on...

not to mention, that you have to use 1/50 or instead of 1/25 and so on with OSS... depending on what you shoot OSS won't be needed (if you shoot sports for instance or want to freeze something with shutter speeds shorter than 1/100...)

I don't understand the math for 2/3 stop in light loss so the numbers you gave is a really good example for me and other people who might not understand it also.

Another example is that my batches of files using the SAL indoor was ISO1250 f1.8 1/80 to ISO3200 at f1.8 1/80. Using the SEL at f1.8 the camera chooses ISO800 f1.8 1/80 to ISO1600 f1.8 1/80. Without the light loss from LA-EA2 the camera chose lower ISOs. However, I still prefer the LA-EA2 for shooting outdoors with my kids. I have a lot more keepers since they are not out of focus. This is just purely for me since I treat my camera as a point and shoot. I feel like the LA-EA2 has keepers like (made up) 80% to my less than 50% SEL ( another made up %) keepers when shooting fast subjects like my kids.

I had a few PMs with blue_sky and he has been really helpful in helping me decide. I ended up with SEL35 and SEL50 for indoors and video shoots. I kept the LA-EA2 SAL35 and SAL50 for outdoor shoots. I sold the SAL85 (and bought the SEL50).

I expected, that the camera compensates the light loss of the LA-EA2, so that a 1/50, f/2, ISO 100 picture with adapter would have the same brightness than without and the ISO quality would just get worse according to light-loss.. maybe it does not compensate and just uses a higher-ISO instead...

Not necessarily. Higher ISO would be used only if it is warranted. For example, SAL 35/1.8 on NEX via EA1 may meter 1/640s for a scene at ISO 200. Replace EA1 with EA2, and it may meter 1/500s, again at the same ISO.

In the end, exposure is determined by simple math:

Brightness Value = Aperture Value + Time Value – ISO Value

The brightness value is determined by the camera’s metering system. For day light, it may be +9 in one camera, +9.3 in another. The aperture value, time value and ISO value will try to match that number.

Actually the Math is more like Brighness Value = (ShutterTime * ISO) / Aperture²

The math I provided uses assigned values (hence "Aperture Value" versus Aperture). For example, f/1.4 is an aperture value 1. Add 1 for each stop (f/2 would be 2, f/2.8 would be 3, f/4 would be 4, and so on), technically a unitless number that simply describes exposure.

For example, here is an exif lifted off Flickr for one of my images:

Exposure     0.008 sec (1/125)
Aperture     f/8.0
Focal Length     24 mm
ISO Speed     100
Exposure Bias     0 EV
Recommended Exposure Index     100
Date and Time (Original)     2012:11:05 10:58:21
Date and Time (Digitized)     2012:11:05 10:58:21
Brightness Value     8.62

Shutter Value for 1/125: 7

Aperture Value for f/8: 6

ISO Value for 100: 5

Bright Value = +8 (close enough to the Brightness value of the scene as metered in the EXIF, as expected out in daylight, just before noon).

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