Different effective exposure from same settings on 2 DSRLs

sqrrl · 11-16-2018, 02:45 PM

Swanlefitte just indicated the Sigma is 2/3rds of a stop slower than the F stop wide open (I'm assuming similar at F4), whereas the Nikon is 4.25 at F4 (which is really close to true). So that could well be noticeable, Also assuming that it's those particular lenses and that DXOMark got it right, sample variation, yada yada.

...but yeah, the different brands do work to different values, Having had hands on most brands over the past few years I've noticed that Nikon is consistently brighter for a particular iso value, and Pentax usually dimmer, It doesn't make much of a difference for actual shooting (assuming the cameras are the same age, format, etc).

**akptc** · 11-16-2018, 05:24 PM - **1 Like**

Thanks everyone for your advice, I appreciate it.

A few minutes ago, I was about retake the pictures with an 85 mm lens on both cameras, in Manual mode, when it occurred to me to look closer at the blades on the Sigma lens - they were not moving as I turned the aperture wheel on the Pentax. To my great surprise, it was the contacts on the K3 that were not perfectly clean! A gentle wiping and I am getting similarly exposed images from both cameras. Whew! I feel very silly for not checking that first.

**UncleVanya** · 11-17-2018, 01:00 PM

Originally posted by akptc

Thanks everyone for your advice, I appreciate it.

A few minutes ago, I was about retake the pictures with an 85 mm lens on both cameras, in Manual mode, when it occurred to me to look closer at the blades on the Sigma lens - they were not moving as I turned the aperture wheel on the Pentax. To my great surprise, it was the contacts on the K3 that were not perfectly clean! A gentle wiping and I am getting similarly exposed images from both cameras. Whew! I feel very silly for not checking that first.

Well. Mystery solved.

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11-16-2018, 02:45 PM	#16
sqrrl Veteran Member Join Date: Mar 2017 Location: Otago, New Zealand Posts: 422	Swanlefitte just indicated the Sigma is 2/3rds of a stop slower than the F stop wide open (I'm assuming similar at F4), whereas the Nikon is 4.25 at F4 (which is really close to true). So that could well be noticeable, Also assuming that it's those particular lenses and that DXOMark got it right, sample variation, yada yada. ...but yeah, the different brands do work to different values, Having had hands on most brands over the past few years I've noticed that Nikon is consistently brighter for a particular iso value, and Pentax usually dimmer, It doesn't make much of a difference for actual shooting (assuming the cameras are the same age, format, etc).

11-16-2018, 05:24 PM - 1 Like	#17
akptc Site Supporter Join Date: Feb 2008 Location: USA Photos: Gallery Posts: 771 Original Poster	Thanks everyone for your advice, I appreciate it. A few minutes ago, I was about retake the pictures with an 85 mm lens on both cameras, in Manual mode, when it occurred to me to look closer at the blades on the Sigma lens - they were not moving as I turned the aperture wheel on the Pentax. To my great surprise, it was the contacts on the K3 that were not perfectly clean! A gentle wiping and I am getting similarly exposed images from both cameras. Whew! I feel very silly for not checking that first.

11-17-2018, 01:00 PM	#18
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,404	Originally posted by akptc Thanks everyone for your advice, I appreciate it. A few minutes ago, I was about retake the pictures with an 85 mm lens on both cameras, in Manual mode, when it occurred to me to look closer at the blades on the Sigma lens - they were not moving as I turned the aperture wheel on the Pentax. To my great surprise, it was the contacts on the K3 that were not perfectly clean! A gentle wiping and I am getting similarly exposed images from both cameras. Whew! I feel very silly for not checking that first. Well. Mystery solved.