Photography News Issue 49

Camera test 37

Photography News | Issue 49 |

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Performance: exposure latitude

Original image







The D850’s auto bracketing feature was used for these nine stops with exposures varying by 1EV and the fitted lens was the 24-70mm f/2.8. Matrix metering and aperture- priority was used and the correct exposure was 1/160sec at f/11 and ISO 100. In Adobe Camera Raw the Raws were corrected by the amount they were under/overexposed by. The same series was repeated using a Nikon D810. Underexposure was well handled and the -4EV and -3EV shots recovered nicely with accurate colours and smooth tonality although noise was evident. This wasn’t bad at all and decreased as Cameras with focus shift features aren’t new and keen macro photographers will probably have a geared head/macro lens set-up to achieve the same result. The D850 offers an automatic focus shift giving up to 300 frames at its full 45.7-megapixel resolution. Stacking is not done in-camera but with a third party software and for this test I used Helicon Focus I tried macro subjects where this feature is best suited and tried it outdoors too. I started indoors with a ruler just to give me an idea of how the feature worked. In the menu you can select the distance changed between each exposure with settings from one to 10 – this is arbitrary and does not relate to any specific distance. Camera set-up was the D850 on

exposure increased. A close, critical look showed that there was still noise in the -2EV compared with the correct shot. This was minimal and readily removed in software. Overexpose too much and you will struggle with successful highlight recovery, as you can see with the +4EV shot here where you can see a familiar grey veiling in the bright areas although the shadows look fine. The +3EV shot was more successful and while the sky has picked up a colour cast in this sample shot, the highlights looked okay although the very brightest areas lack detail. With the +2EV and +1EV shots, both recovered well a tripod and fitted with a 105mm f/2.8 macro lens focused using live view at 0mm with the camera’s focal plane 50cm from that point on the ruler. The camera was set to shoot fine JPEGs, ISO 100 and aperture-priority AE with the lens wide open which gave an exposure of 1/30sec. The ruler was lit by an LED light panel. I tried shift settings of 1, 5 and 10 shooting 30 pictures, returning the lens to the 0mm focus point on the ruler each time. I also set the D850’s electronic shutter for vibration-free release. Afterwards using Helicon Focus, the 1 setting gave sharpness from 0mm to 33mm, the 5 setting stretched sharpness to 60mmwhile the 10 setting gave 165mm of depth- of-field. Next I reset the focus and set 300 exposures, the maximum, to see what was possible. The first




Images The D850’s Raw files showed a good exposure latitude with good recovery possible for under and overexposed shots with minimal artefacting.

enough to match the image quality obtained from the correct exposure. Comparing the D810 with the D850 exposure bracket showed there was little difference with the underexposed shots where

both showed a low level of noise in the -4EV and -3EV shots. With overexposure, the D850 seemed to fare marginally better with cleaner highlights while neither camera could copewith +4EVoverexposure.

To sum up, the D850’s Raws have a very good tolerance to exposure abuse and you could underexpose by -4EV and overexpose by +3EV and salvage acceptable results with some afterwork in software.

For Performance: focus shift feature

go with this I got 300 shots in about three minutes. You can see the stacked shot bottom left. The 300 images stacked well – and this was without any afterwork apart from using Helicon Focus. It’s not perfect – weird effect at the front – but the feature (and software) did remarkably well. I next tried an old circuit board, again with the 105mm macro lens and very close in. I started with the lens’s smallest aperture for maximum depth-of-field and this gave good but not total front-to- back sharpness. Not only that but diffraction at such small apertures impacts on sharpness and softness was evident in this shot. For the test, I set maximum aperture focused at the very front of the circuit board, set the focus change to 1 and 150 frames. Once merged, as you can see here (above right), the effect is impressive. Finally, I took the D850 outside to see if there is an opportunity to use this feature for scenics when the conditions suit. You can’t have any movement between exposures, for example, so flowing water and windblown trees are out – unless youwant a creative effect. Apossible option is to use a fast shutter and as few images as possible to get a sharp final image. I tried several outdoor scenes including a few which I knew stood not a snowball’s chance in hell of

automatically stops when infinity focusisreachedsodon’tbesurprised if it stops at 23 shots when you have set 100, for example. Also use the Starting storage folder option so that each set of exposures is stored in separate folders on the card. I don’t focus stack because I have neither the patience nor the need. That need could change though thanks to the D850. It makes focus stacking simple and it works (you need a good stacking software or Photoshop skills). I probably wouldn’t buy the D850 just for the focus shift feature, but I would certainly use it if I owned one because it has openedmy eyes to opportunities I hadn’t considered before. Images This is the final stacked shot – in the end I used 140 JPEGs through Helicon Focus. The two accompanying shots above show the two extremes.

working, ie long focal length, close foreground and far background. As expected, some scenes didn’t work but some did. A statue with a wall ten metres behind came out well while a distant scene with a foreground fence two metres from the camera shot with a telephoto lens didn’t. To be fair, though, in the latter’s case with effort in software I could have got a decent result. Afewthingstobearinmindwhen using the D850’s focus stacking. Start by focusing at the closest point you want sharp and remember to refocus after each completed set of exposures and the wider the focus range the more shots you will need. The limit is 300 and if you are any doubt set that because the camera

The 300 images stacked well – and this was without any afterwork apart fromusing Helicon Focus

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