The following examples are from a test made with a current Sony A7s camera that compares the resolution and detail of identically timed exposures, one set with camera, the other timed with Bulb.
These screen images from Lightroom show the comparison exposures at a 1:1 view and 2:1 view. These are from raw files, straight out of the camera, with no development adjustments.
In early May, 2017 I purchased a new Sony A7S camera body from B&H PhotoVideo. A couple of days after it arrived I was alarmed to read of a problem astro-photographers were having with the way that Sony’s proprietary software dealt with longer and bulb exposures. Although the alarm seemed to concentrate issues with the newer models: A7RII and A7SII, there was documentation on the internet that said there were also issues with the first version of the A7S, the one I just bought. Ian Norman, lonelyspeck.com wrote a blog detailing why he no longer could recommend these Sony models to his astro-photography followers. I had read that the Sony A7S did not suffer any “star eater” issues when you chose exposures from the camera’s menu. However, it was said that if you made the same length exposure using Bulb, the Sony software then interpreted the fainter stars as noise artifacts and either removed them or at least dimmed them so much the overall photograph appeared to have lost many stars. It also was said that the appearance was quite noticeable. Many photographers had run tests and evidence of this diminishment of resolution and quality when using bulb was all over the internet.
I contacted Sony’s technical department and spoke with a representative. I was told that Sony was aware of the problem and “they were working on it, trying to find a solution.” However, after trying to pin them down on the bulb issue concerning my model, I was reassured, “there is no problem with the A7S (original model), only issues with the 2nd generation, the mark II models. I told the rep that was not what I had learned and that I would post the information she gave to me, which I did on the lonelyspeckblog site.
Last night, I did my own testing with the new Sony A7S. I made comparison photographs at the same f/stop and shutter times, 15 secs, with one chosen by the camera menu and the other made with the bulb. I made one pair with LENR on and one pair with LENR off. I downloade the raw files and examined the un-adjusted test shots in Lightroom. There was an immediate and obvious diminishment of quality as well as many missing or ‘softened, darkened” stars in the bulb exposures compared to the camera-timed exposures. I will be sending the images to Sony after I speak with them. Keep your fingers crossed. All of us hope Sony will fix this unacceptable firmware for our cameras.