Photoclub Alpha

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:

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:

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

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.

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.

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:

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:

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:

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’):

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:

- DK

Sony has announced the Alpha 850 today, without a press conference, but via email to editors. The press release follows, confirming pretty much everything we have already been able to reveal about the 850. One exception – it does have dual BIONZ processor, not single, just a slower image throughput perhaps due to clock speed, buffer, processing firmware changes. We must hope that the slower capture rate is accompanied by superior image quality, as that is a real possibility. I have marked in bold any phrases which I think might indicate something new. Apparently the body-only deal is to appear one month before the kit.

Sony has announced the Alpha 500 and 550 today with an official release to all press. No press conference was held for the UK press and any advance information received has been given indivudally to journalists. There is a press event tonight in London but this is VERY specifically stated to be for trying out the new Cyber-Shot models at twilight. The official release follows.

The new Alpha 230, 330 and 380 models are radical ergonomic redesigns of the existing 200, 300 and 350 series. There is a 15% reduction in size (volumetric) and weight, an update to the styling, and a completely revised user interface with graphic representation of setting adjustments – with a built-in ‘handbook’ to accompany the modes and options. They also have mini-HDMI image output, compatible with Bravia TVs and with interactive software inside the camera to allow the Bravia’s own remote control to change, orient and zoom into images (Bravia Sync). Twin card storage is MS ProHG Duo/SD and only one card is usable at a time, with a hardware switch to change slots. A smaller battery type (shared with the HX1 Cyber Shot) is used. A new self-timer drive mode grabs a quick burst of 3 or 5 frames, cutting the chances of spoiled portraits and groups shots when someone blinks at the wrong moment.

The new flashgun HVL-F20AM operates as a wireless flash controller for the full-frame α900. “While Sony’s flagship DSLR does not have its own integrated flash, the HVL-F20AM can be used as an inexpensive trigger for wireless remote flash heads” according to Sony UK.

Tamron Co., Ltd (Mr. Morio Ono, President), a comprehensive manufacturer of optical products with its head office in Saitama City, has announced the development of the SP AF60mm F/2.0 Di II LD (IF) MACRO 1:1 (Model G005), a life-size macro lens designed exclusively for digital SLR cameras with APS-C size image sensors* that offers a fast maximum aperture of F/2.0. (Text here is directly from their press announcement).

EDINBURGH PHOTOWORLD DAY

A Photoworld Day has been arranged for Sunday 22nd March in the premises of the Edinburgh Photographic Society at 68 Great King Street, Edinburgh. Athough primarily aimed at subscribers to Photoworld, former Minolta Club members and users of Sony digital cameras, the meeting is open to others interested in photography.

There is a white paper by Sony Semiconductor on the imaging processing which I think is in the HX1, http://www.sony.net/Products/SC-HP/cx_news/vol55/pdf/featuring55.pdf. I assume it is the IMX-032 CMOS sensor (http://www.sony.net/Products/SC-HP/cx_news/vol55/np_imx032cqr.html) mated to a CXD4109AGG image processing chip. There seem to be some interesting techniques employed, multi-plane synthesis to combine several frames for low light and HDR capture.

With the IMX-032, it is interesting to note that the on-board programmable gain amplifier has a gain value of up to 18dB or a factor of 8, so if base ISO is 80, then maximum “analogue” ISO is 640. If we compare the IMX-032 versus Sony’s first column ADC CMOS chip (IMX-017), the IMX-32 has an 11.8% better photo-electron efficiency per unit area (2300e per 1.75 micron square pixel compared to 4500e per 2.5 micron square pixel). Might be a sign that Sony is improving the process and design used to make their CMOS chips.

The backside illuminated chip is called the IMX-061, http://www.chipworks.com/uploadedFiles/Aliased_Pages/CMOS_ImageSensors_Spotlight/Chipworks%20-%20Sony%20IMX061%20EXR-0902-813.pdf
6MP and 1.75 micron pixels in ClearVID (45 degree) layout with a 1:6:1 RGB Bayer filter array, sacrificing colour resolution for spatial resolution.

The Nikon D90 chip is called the IMX-038 (not the IMX-021 as for the A700), so this suggests it has significant revisions compared to the IMX-021 (possibly linked to LiveView and HD Video?).

– Dr Daniel K. L. Oi

This set of full size shots was taken with the still life left set up, because the Nikon and Canon cameras were not here at the same time. It compares the A900, 5DMkII and D3X using the converters supplied by the makers – Image Data Converter SR2, Digital Photo Professional, and Capture NX2. Each small image in the article can be clicked to open a Level 10 quality full size JPEG – beware, the largest is over 13MB of data.

Following the review on dPreview – more than anywhere else – Sony’s extremely poor JPEG engine with its associated wide radius chroma blur and strong luminance smoothing noise reduction has proved to be a dog well capable of biting its master. Definitely a dog, anyway. But this performance is not what the camera can really achieve. In fact it’s perfectly capable of delivering good high ISO shots in typical situations.

If you are on the verge of making a decision, I’m here to help your think clearly – even if it means breaking some cherished behaviour patterns. I am going to help you think of the Alpha 900 not as a logical progression from the 700, but as a different camera system entirely.

AWARD winning event photographer Keith Trainor – winner of the first ever UK Event Photographer of the Year title in the annual British Professional Photography Awards – hits the road with Sony shortly in the UK to bring a profitable, high energy new line of business to established photo studios and new business entrants.

This article was originally published in Photoworld magazine April 2008. It discusses the reasons for choosing between the 18-70mm, 16-105mm, 16-80mm, 18-200mm and 18-250mm kit lens choices for the Sony Alpha DSLR system and has been updated as necessary from the original text.

Alan Hess is the author of a new field guide to using the Sony Alpha 700, published by Wileys, with 281 pages and the usual contents covering basic photographic techniques as well as the camera’s operation.

The cost of the guide is 16 Euros by mail order from Research & Markets of Dublin website; the title is ‘Sony Alpha DSLR A700 Digital Field Guide‘.

Following announcements that Sony has developed a backlight technique to enable extremely low noise exposures, we receive this press release which may or may not be related – a Sony CCD astrophotography camera capable of one-hour exposures and programmed sequences. Resolution seems a bit basic though.

Here’s a question which came in to my email just now:

“Could I process a RAW file in Photoshop to achieve a similar effect as if I had used a Polaroid lens filter?
Or would I be better just using the Polaroid filter?”

The answer is that you can never imitate the effect of polarizing light (which changes the way reflective surfaces look, and deepens or lightens the sky blue according to the zone of the sky relative to the sun’s position. But you can use Adobe Camera Raw (CS3 versions) to deepen skies you never thought could be rescued.