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Alpha 550: sky noise, exposure and Auto ISO

My review of the Alpha 550 has caused controversy because of the blue sky noise. I might as well say that over the last week, I’ve used the 550 in a wide range of conditions – some very bad conditions included – and its failure to match ISO 100 finesse would not worry me at all. The performance at higher ISO settings is so much improved it’s worth putting up with the minimum of ISO 200, and a touch more noise than the best ISO 100 results from the Sony CCD sensors.

Even so, something was clearly happening during the period of sunnier weather used for my earlier A550 tests. I used Auto ISO initially, because I had not realised how readily the camera will select settings right up to 1600. Auto ISO has thrown up some surprises. Here’s something to consider:

autoISO0-200variations

Please note that although ‘process’ symbols are shown with these Adobe Bridge/ACR images, the defaults were restored and then each picture was set back to defaults. They are all shown relative to each other in density, the image preview built by ACR. There is no question of DRO or any other tonal setting interfering with the apparent exposure – DRO does not affect the .ARW file, ACR discards any DRO generated embedded preview in my setup prefs, and DRO was not being used anyway.

It has already been noted by other reviewers that the A550 has considerably more headroom without clipping, even compared to the A350 which was already a top-ranking camera for dynamic range. This is what I meant when I compared its default images to Canon with Highlight Tone Preservation switched on, or KM/Sony older models using the Hi200 setting. This can mean that the A550 is really ISO 100 at its lowest on-sensor gain setting, but the exposure system is programmed to underexpose by a stop and the post-processing (BIONZ) is set up to boost the gain.

Why would Sony do this? Perhaps they read the many posts referring to the Alpha 900 and 700 ISO settings. The on-sensor gain controls the main ISO steps, but a rather cleaner post-process gain adds the 1/3rd step intervals. Experienced Alpha 900 users set ISO 320 manually because the sensor is at its optimum at roughly ISO 160 (DxO tests bear this out). The standard ISO 200 setting can produce more noise than ISO 320 because two different digital stages are used to produce the gain.

In search of superior high ISOs, they may have realised that the early gain stage (on the chip assembly) is inferior to the later BIONZ processor, and you can indeed get better high ISO by underexposing a lower ISO setting, then processing it with clipped blacks. That’s a Nikon technique, which has served them well. It’s also a technique used by experienced DSLR owners.

Now consider the four shots above. They are all taken at ‘ISO 200′ but the camera was set to auto ISO. Other shots in the same set show ISO 250, 500 etc confirming the auto ISO was in operation. They are taken in the afternoon in Scotland, so it is fairly near to the end of the day for sunshine by 14:49hrs, around an hour away. But the two locations at 50 minutes apart, 14:00hrs and 14:49hrs, should not have the extreme variation in exposure shown here.

Just what is going on for an exposure of 1/400th at f/11 to look correct at ISO 200, with the dark sandstone buildings of Jedburgh at the end of October? 1/400th at f/11 is the ISO 200 exposure for full sunshine in midsummer (aka f/16 light). You hardly ever find f/16 light in Britain unless you are on the beach, surrounded by pale concrete, in a field of golden corn or out on a lake.

50 minutes later, exposures range from 1/60th at f/11 to 1/100th at f/11 – that is, more or less, from two to three stops more. In fact these exposures are in line with what I would expect, it’s the 1/400th at f/11 which is the odd one out. I have no evidence to suggest that my CZ 16-80mm has an aperture which fails to stop down consistently.

Now look at some sky samples:

Here is an in-camera JPEG version which shows less noise – the in-camera process is equal to using much stronger NR in raw conversion than I would normally choose for ISO 200:

incameraJPEG-iso200clip

Now for the same processed from raw – notice that despite the noise, it is slightly more detailed or sharper:

skyiso200-400th-f11-acr5p6-default

This is a reprocessed second version of the original noisy sky instance. Here, I have used Adobe Camera Raw 5.6r1 defaults, which include some basic sharpening and also 25 on the chroma NR scale. No exposure adjustment is made at all. This view, by the way, looks more or less due north and it is not a case of a brighter sky underexposed; also, the stone and the chimney pots look normally exposed.

skyiso200-100th-f11-acr5p6-default

This is the 1/100th at f/11 shot, processed exactly the same way. It’s interesting in that I expected to see much lower noise, but in fact it’s much the same. The sky density is similar as well. The view is slightly more towards the east. While my Alpha 380, 200, 100 and even 700 shots are capable of showing blue sky noise at ISO 100 and as much as this as 200 it’s not as obtrusive.

skyiso200-60th-f11-acr5p6-minus1evcorr

Finally, this is the 1/60th exposure – perhaps more what would be expected at ISO 100 in this light with f/11. Here, I have set -1 EV exposure reduction in Adobe Camera Raw to get much the same final sky tone density. The noise is lower.

Checking other images I’ve taken since, I am now suspicious about the Auto ISO function in the Alpha 550, and whether it reports the gain applied to each shot accurately. It’s hard to reconcile the same ISO 200 setting shown in EXIF with the range of exposures encountered, and the actual exposure of the raw file. Yet ISO 250 was also selected for this shot taken a few minutes before the chimney shot:

This is also included in the main report (click image to view full size on pBase). If I darken the sky as much as the other examples, I get noise similar to the 1/60th ISO 200 clip, or better.

Since making these tests, I’ve started using the Alpha 550 only on fixed ISO settings, with some misgivings as intermediate gain like ISO 250 or 320 might possibly be yielding better results. I just feel something is happening in the BIONZ stage, perhaps involving analysis of the Auto ISO images and compensation for deviations from the reported EXIF Auto ISO setting. This is just a hunch. Fixed settings seem to be equal to the worst case from Auto ISO. Here’s a textbook example, 1/125th at f/16 for a blue sky on November 3rd, facing due north, at 14:19hrs, ISO 200 fixed setting, ACR 5.6 defaults as above:

iso200fixed-125th-f15-acr5p6default

The answer seems to be to overexpose your manual ISO 200 shots by not simply one stop, but as much as two stops when shooting raw. At least if Adobe Camera Raw is used, recovery of normal tones (not burned out highlights) will fully restore the exposure from 1 or 2 stops over depending on the subject.

Here is an overexposed image, taken at 1/80th at f/10, ISO 200, in mid-day sunshine:

1p7stopsover

Below is what the sky looks like in a normally exposed image (1/250th at f/10), processed using Adobe Camera Raw defaults (including sharpening at 25/1/25/0 and NR at 0/25), looks like:

iso200-normalexp-250th-f10-acr5p6defaults

And here, finally, is what an adjusted ACR process from the overexposed image looks like with sharpening turned off, NR set to 25/50, exposure and brightness determined by the simple process of using Auto (which can be set as a default in ACR if you want to consistently make generous – over – exposures ‘to the right’):

plus1p7exposure-iso200-80th-f10-acr5p6adjust-nosharp-NR2550

This is much more how I expect to see a sky looking from the base ISO of a 2009 DSLR release, viewed at 100 per cent. From this stage, different types of sharpening can be applied to suit resized versions for different purposes.

Results with other raw converters, as more become available for the Alpha 550, may be finer in noise structure than ACR or may offer less scope for overexposing – ACR is well known for its ability to recover highlights. I do not intend to go much further into this with tests of converters, but I hope I have shown how the ‘true ISO’ of the A550 is difficult to pin down especially in Auto ISO mode, and how it is possible to benefit from the great high ISO performance of the camera (just use it!) and at the same time secure good low ISO results for travel and landscape shots where a clean blue sky is important.

It’s important to note that in-camera JPEGs will not necessarily show similar noise levels. If they do it’s not so easy to fix without using NR software. I prefer to shoot raw for many reasons.

So, why not be very happy with the Alpha 550 as a choice? Here are two pictures. You can view the full size Alpha image, and the Nikon D3S image resized to match 14 megapixels, by clicking on the smaller size here. Of course the Nikon image is better, though 1/250th at f/5.6 and ISO 400 is more of a step away from 1/250th at f/9 and ISO 200, and I’m not sure the light was SO different on the two occasions:

Alpha 550-250Sigma-iso200-web

Nikon D3S-400mmf2p8Nikkor-iso400-web

- DK


Sony Alpha 550 Review: highs and lows

My review of the Sony Alpha 550 was supposed to appear at the end of November, allowing one week abroad in good weather with plenty of subject-matter, in Tenerife. Sadly that trip had to be cancelled, and the Nikon D3S arrived for review on the day we were meant to have travelled. So, with far too much work to do on the D3S, I’m “going to press” here with my initial thoughts based on a fairly short time using the Alpha 550. There are 11 pages in this review, please use the Next Page navigation at the end of each page to continue reading.

PLEASE NOTE: this website uses a rating system where readers can rate the posts, like this review. This rating is NOT my ‘rating the camera’! I have read elsewhere that I ‘gave the camera 4.83 out of 5′ – that was the rating readers gave my review… sorry, this is very confusing, I had not realised how easily it could be confused. We have had the post-rating system for a long time and it’s a standard feature on many Wordpress based sites. I do not want to remove it (along with the ratings) so please accept this apology for incorporating a dangerously confusing ’star rating’ here.

sonyalpha550-2

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Lightroom 3 Beta released

London. — October 22, 2009 — Adobe Systems Incorporated (Nasdaq:ADBE) today introduced Adobe® Photoshop® Lightroom® 3 beta software for Macintosh and Windows®, a public preview of new and improved functionality to be delivered in the next major release. Lightroom is the essential digital photography workflow solution, helping serious amateur and professional photographers quickly import, manage, enhance, and showcase all their images from one application. Available as a free download on Adobe Labs, Lightroom 3 beta delivers a preview of new tools that will be in Lightroom 3, including more intuitive importing, unparalleled noise reduction and sharpening tools and enhanced slideshow capabilities.. Adobe encourages photographers to test this early selection of new features and provide the product team with their feedback.

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Could Sony get ‘DxO Inside’?

I don’t have an Alpha 500 or 550 here yet, even though Photoclubalpha has been second in the Google search results for ‘Sony Alpha 550′ for some time and remains so as I write (the New York Times is first). That’s not bad for a Wordpress blog website which does NOT employ the services of the dozen or so ’search engine optimisation’ experts who contact us each week! Hopefully we’ll have a review camera very soon, preferably the 550.

In the meantime, a few samples have been posted on various sites which show the raw conversion engine of the camera/s (not necessarily the JPEG compression stage, as always seems to be assumed) has been radically revised. Sony call this ‘enhanced BIONZ’ and I think there’s a clue to how it has been enhanced in the relationship of Sony Europe and DxO Labs, the French company which specialises in in-camera process analysis and development.

Click to continue reading “Could Sony get ‘DxO Inside’?”

Sigma 18-250mm f/3.5-6.3 DC OS HSM

Tamron’s 18-250mm lens – later adopted by Sony – was so good that it really takes some effort to beat it. Sigma has put that effort in, but the cost is a very much larger and heavier lens. If all you got was some better performance, it might not be all that exciting. But you get potentially superior anti-shake through its built-in OS, and faster focusing with HSM, the Sigma equivalent of SSM.

Click to continue reading “Sigma 18-250mm f/3.5-6.3 DC OS HSM”

Crop or cram? Pixel density versus the big view…

The Alpha 900 offers an unrivalled view through its 100% prism finder. The extra brightness, as well as the size and clarity, make most subjects far easier to photograph well. For some users, however, the full frame camera brings a disadvantage in terms of reach and resolution. You need lenses 50% longer (and thus twice the size, and four times the cost!) to fill the frame with the same distant sports and wildlife subjects. I don’t need to remind anyone how popular these two subjects are with amateurs, and sometimes, how important to professionals.

Click to continue reading “Crop or cram? Pixel density versus the big view…”

The Sony Alpha 380 – review

My Sony Alpha 380 was supposed to arrive before July 13th according to SimplyElectronics.net – via Amazon – claiming UK despatch of 2-10 days delivery after debiting my card on July 6th from a July 3rd order. Well, it didn’t arrive by July 21st, and after some email exchanges I have apparently obtained a refund for the charge they made for an item they did not have (though this was still showing as ‘processing’ in August). Warehouseexpress.com had got the A380 plus 18-55mm kits  by that time, for £10 less, and delivered in 24 hours. Update August 9th: under a month later, the warehouseexpress kit price has fallen by 10% (£50) to £548 inc VAT.

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Alpha 850 – 24 megapixel 3fps in 900 body

Sony’s new Alpha 850 will be identical to the Alpha 900 in size, handling and external design – including the omission of onboard flash. The camera, expected to be launched before September, uses the same 24.6 megapixel CMOS sensor as the Alpha 900 but has – it is rumoured – only a single BIONZ processor, and a very slightly modified viewfinder. It is shipped without the Remote Commander (this becomes an optional extra) indicating that minimum retail price is Sony’s aim.

fotobrenner2

This is a screen grab from Fotobrenner.de in Germany who have the body only offered for €1999.00 and the kit with SAM 28-75mm f/2.8 new lens for €2699.00. As listed that makes the body about 10% more expensive than the current street price of the Alpha 900 – indicating either that the A850 prices are RRP and will rapidly fall, or that the A900 is about to get a price hike. They offer the A900 for €2499.00 and that would – pro rata – make the UK street price for the A850 about £1599. Please note: though the 28-75mm picture is authentic, the body shown has the AF switch set to C – just like the Sony shots of the A900 issued to dealers. Maybe they would do this for all packshots for some reason, maybe it was chance – more likely. It would be unlikely to happen again for the 850 shot so I reckon this is shopped.

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Sigma classic 400mm tele quick rechip

There is no need to dismantle the mount of the original series Sigma AF TELE 400mm f/5.6 lens, to bring non-functional versions (old chip) up to speed with later film and current digital SLRs. The whole process takes under five minutes, and requires two tools – a small Philips screwdriver, and a precision end cutter.

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Sony Alpha 900 and Nikon D3X raw file noise comparison

Like Mike Johnston writing in The On-Line Photographer, I’m aware that any attempt to line up one or more cameras and show comparison images or make judgements is on to a loser from the start. And any webmaster who puts an external link in the first half dozen words of a new post is losing the plot too! But here, for what it’s worth, is the first line-up of results processed using the same software from A900 and D3X uncompressed raw files converted without sharpening or noise reduction.

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Alpha 900 launch: Press Conference Part 4

Duncan McEwan spoke, in his usual very steady and friendly manner, about his experience of using the Alpha 900. He showed a selection of images taken – remarkably – over a period of just 10 days preceding the event, using a 24-70mm CZ and his own 70-200mm Minolta SSM. Here is his own ’script’ for the presentation, with a small selection of the images.

Click to continue reading “Alpha 900 launch: Press Conference Part 4″

Alpha 900 and photokina: Part 1

OUR final production Alpha 900 body arrived on Saturday September 20th, and went along to photokina 2008 on Monday 22nd where it was used in a routine way – without flash – to take whatever pictures were needed for magazine reports. Sometimes it can be better just to use a camera on whatever difficult or poor subjects the world throws at you, than to devise impressive test situations.

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Alpha 900 HDR bracketing

The Alpha 900 – and indeed the Alpha 700 with new firmware v4 – offer a three-bracket sequence at a 2 stop interval to enable HDR blending, usually from static tripod-mounted views. At the Edinburgh Alpha 900 launch, I braced myself firmly against an open window, leaning out over the street, and tried an example hand held.

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Repairing an image by cloning from another

MANY photographers habitually use layers from everything. I don’t! In fact, I try to minimise my time spent on post-processing shots for stock library sale, and work very quickly. If it needs complex setup or demands working using layers to be able to go back and change things, I’ve probably already wasted too much time. Here’s an example of an Alpha 700 shot created from two slightly different versions, and how it was done.

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Sony Alpha 350 – a Creative Review

The introduction of a £399 (street price, RRP £449) DSLR with 14.2 megapixels – with or without a useful type of Live View – should have been applauded by reviewers. It’s the single most important point about the camera. No other DSLR approaches this image size and resolution at such a low price.

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