Tag Archives: Sony A1

Sony FE 28-60mm f/4-f/5.6 Close up tests

The Sony 28/60mm f/4-f/5.6 is a small lens that was initially provided a kit lens for the Sony A7C a 24 megapixel low end camera.

There have been several discussion on underwater forum about the performance of water contact optics adapters to see what is best etc etc.

However I could not find any proper resolution test for this lens so I thought of giving it a go myself.

Dpreview has a decent sample gallery.

Official Test Data from Sony

You can find the lens specifications on Sony website https://www.sony.co.uk/electronics/camera-lenses/sel2860/specifications

The lens is nothin special mostly plastic but it is weather sealed. It has only 7 aperture blades so this is a lens for snapping around happily topside but not exactly a top of the range device.

The construction comprises 8 elements in 7 groups. Sony publishes the MFT resolution chart for this lens on their website.

Sony has some strange nomenclature however for reference images [3] is at 28mm f/4 and [4] 28mm at f/8.

[5] and [6] are at 60mm less interesting for underwater purposes.

The red lines indicate a resolution of 10 lp/mm which is a really low value (the A1 sensor resolves up to 120 lp/mm). The blue lines indicate 30 lp/mm, The [10] indicates Sagittal and [11] meridional lines.

Read this excellent article from Nikon on MTF to understand how to read the graph.

What graphic [3] is telling us is that as we move away from the centre of the frame both sagittal and meridional lines drop in contrast.

Graph [4] shows that at f/8 the deterioration as we move towards the edge of the frame is more contained neverthless meriodional lines drop considerably.

While we cannot conclude how this lens will compare to other lenses what we see from the MFT is that the 28-60mm as tested performs better at f/8 than it does at f/4 when used at 28mm. In fairness it seems to be the same situation at 60mm but the gap between f/4 and f/8 is much less.

I found a good test here aligned to what you will read here to a good extent.

Practical Home Made Test

I sourced a cushion with a complex embroided decoration.

With the camera on a tripod a remote release and one off camera strobe I took shots at f/4 f/5.6 f/8 and f/11. I run tests with the camera poiting at the centre with field of curvature and off centre with the centre of the cushion at the edges.

Here are my findings.

Centre Performance

800% center crop Left f/4 Right f/5.6

As anticipated the lens is not sharper in the center when wide open.

800% center crop Left f/5.6 Right f/8

At f/5.6 the difference with f/8 is minimal

800% center crop Left f/8 Right f/11

Stopping down to f/11 gives a mild deterioration.

Looking at centre I would say f/5.6 to f/8 is the way to go.

Edge Performance

Let’s see the situation at the edges.

400% edge crop Left f/4 Right f/5.6

f/4 was not better in the centre and is pretty bad at the edge.

400% edge crop Left f/5.6 Right f/8

Stopping down to f/8 sees an improvement the situation is not great though.

400% edge crop Left 8 Right f/11

At f/11 the edges are ok.

So looking at edge performance I would use this lens between f/8 and f/11.

Full resolution examples here

28-60mm 28/4
28-60mm 28/5.6
28-60mm 28/8
28-60mm 28/11

Consideration for use underwater

Looking at the lens in isolation I would think the starting point is f/8 with one stop up or down depending on the situation. This lens is not good wide open and beyond f/11 resolution starts to drop.

Alex Mustard has taken some comparison shots between the WACP-1 and the WWL-1 and his conclusion is that the performance of the WACP-1 at f/4 is similar to the WWL-1 at f/6.3. Based on my tests I would frankly not bother shooting this lens at f/4 the quality is just not there. The starting point would be f/8 and f/11 does not deteriorate edge performance that much but of course needs more light. Wider aperture like f/5.6 may be good for blue water shots.

My opinion is that this lens will not offer amazing sharpness no matter which adapter you use and is likely to stop at 26-28 megapixel in reality if not less depending on conditions, assuming your starting point is a camera with more than 40 megapixels.

it would be interesting to compare the water contact options at the aperture of f/8 and f/11 but we can safely conclude that the 28-60mm is not going to be a champion for ambient light shots in low light because the performance wide open is not great.

If I had to invest into the best image quality I would be looking at a different master lens and a larger water contact optic such as the WACP-1.

Additional Information

I have created some stir on the fact that this lens is quite weak but it actually is.

I took the same shots with my 24-70mm GMII and I can say that there are 3 stops difference at the edges between those lenses

The 24-70 at 28mm at f/4 is the same of the 28-60mm at f/11

This is a 200% crop of the edges

Left 24-70 GM at 28mm f/4 Right 28-60mm at 28mm f/11

Sony A1/A7S3 : Video Codecs

The A1 and A7S3 share the same codecs and format for (4K) video. The cameras have been around a few years however I could not find a proper analysis of the codecs. You can find the usual YouTube doing some qualitative analysis mostly lacking rigour and based on static charts which is not really sufficient.

I did this analysis on my A1 but the results hold for the A7S3.

So I decided to give it my own attention and you will get my findings in this post. I do not shoot 8K and for this format the choices are limited anyway to XAVC HS so not much to go about.

XAVC Basics

Sony has like many other brands their own codec for in camera video recording and their version is called XAVC.

You can find some more detailed information on Sony Pro Site.

Take into account that the documentation does not consider the newest XAVC HS based on HEVC coding.

In general terms you have two options:

  • Intra frame -> each frame is self contained and does not depend on other frames, the clip is a collection of compressed images
  • Group of Pictures (GOP) -> frames are a combination of 1 reference intraframe for each group of pictures and multiple P and B frames which means respectively Predicted and Bi-directional predicted.

More on GOP on Wikipedia.

GOP video is temporally compressed and more efficient in terms of space however it takes more computing effort to decode and encode.

Depending on the number of reference Intra frame inside a GOP you can have more or less prediction errors which manifest as noise or artifacts. So if you want to make sure that you don’t get motion artifacts you need to use an intraframe which means using more space.

A1 Codec Options

As mentioned XAVC gives you both options and the A1/A7S3 can record Intra video up to 240,250,300,600 Mbps depending on the frame rate Sony approach is 10mbps per frame.

GOP is more compressed and has 140,200,280 Mbps respectively for 24/25/30, 50/60, 100/120 frames per second. Please note higher frame rate of 100/120 fps is only supported on GOP formats as it would otherwise reach 1.2 Gbps.

Higher compression does not mean at all lower quality, analysing all codecs using ffprobe you can see that the individual Intra frames within a GOP structure are larger than the Intra frames of an All-Intra clip at higher bit rate. However due to the nature of GOP there will be potentially motion prediction errors and more noise.

A1 Sample Video

I ran some tests of a music box both static and in motion using Slog3. I warmly recommend using Slog3 for all your video as it the log compression achieves less bit utilisation and makes the video compression even more efficient.

From what I can see (there is a small focus error on the XAVC S moving part) there are minimal difference in motion handling and minimal differences on noise.

I checked each clip with Neat video using the same reference area. XAVC S and HS return the same amount of noise.

XAVC S
XAVC HS

While All intra for some reason has less noise. I believe this is because the prediction introduce some small error themselves.

XAVC S-I

Considering those shots are taken at ISO 4000 there is not much to complain. ISO 4000 in Slog3 is the point where dual conversion gain goes into High gain. If you use a standard profile this would be 500. I do not recommend shooting the A1 or A7S3 in any other picture profile than slog3.

Visual Differences between Codecs

I frankly cannot see much of a difference between those codecs, I have also shot a few sequences in APSC in equivalence so at ISO 2000 and f/3.2 instead of f/4.5 and I could not see much difference except APSC has a bit more noise as expected.

Analysis

The following table shows some key data points and my observation based on a series of 50 fps video test shots with the A1.

Sony A1/A7S3 Codecs

You can see that the key difference between the codecs is the bitrate, the edit effort (how taxing is on your machine) and the noise.

What codec you will use depends mostly on practical considerations as the difference in image quality are intangible.

The HS format which is based on HEVC has a single reference frame each second which means this codec is really for static scenes as most frame are predicted. XAVC HS biggest limitation is the lack of 25/30 fps options it is a good choice for 24 fps and it does not completely stall your machine in the editing.

The S variation is good in terms of space saving as well as generally being effective for motion however it is the hardest one to edit. If space is a problem and you are happy to convert or edit natively XAVC S is a good option. If you need something that can go on for long and manages almost all situations the XAVC S should be your choice however unless you have a workstation that supports accelerated H264 10 bits 422 (and there are not many at all) you will need to convert to an intermediate codec spending more time in post processing.

Finally the S-I All intra is the one that has the least noise and is more demanding on your memory card but is the easiest one to edit and play despite the higher bit rate. If you shoot wildlife, actions, or use gimbals and your default is 50/60 frames per second, the All intra codec XAVC S-I is the best option but it does not support higher frame rate so you would need to switch to another codec for those situations and this should be the XAVC S as it manages motion better.

I have not done a test with a gimbal but those scenario where a lot of pixel move in the frame is much more taking than my music box test.

Conclusion

Although the choice of codecs is not as rich as Panasonic cameras and there are no formats other than 16:9 there are no quality issues with the A1 and A7S3 codecs as long as you shoot in Slog3.

Obviously there are options for external recording although this is not the best option for run and gun and that would give you ProRes 422 HQ or ProRes RAW with huge files easier to edit. In the future I will do a comparison between the internal intra codec and ProRes 422 as well as ProRes 422 HQ so stay tuned.

If you have any question leave a comment and I will follow up.

Sony A1 : Video Resolution

When you buy a new camera some time after the initial release date you are lucky to find all sorts of videos of other geeks like you that have been testing.

I was referred to this video that shows quite a few quirks of the Sony A1. Gerald has since confirmed the A1 video is binned not line skipped.

You can’t always rely on third party so here are a number of geek tests.

The first question was do you need to shoot ASPC or full frame. APSC is scaled while full frame is binned which means the first may look better than the second but will have more noise.

Pixel Binning

As usual there is no official documentation of the camera inner workings but this diagram should help explain a few things.

On the upstream the potential flow for a classic bayer filter camera to accomplish binning (it is a guess). On the bottom what a mobile phone may be doing.

In the first case binning results in a reduction of resolution and potential artifacts. In the second only a reduction of resolution.

Now one of the question is what if we just crop the sensor in APSC and then scale down will it look better?

I have done exactly this test and the answer seems to be no.

UHD binned vs APSC scaled

In theory the binning should look much worse but what I have seen is that moire kicks off for both at around 2x the focal length of the other. So if APSC gives moire at 50mm full frame will give it at 100mm. The full frame moire is more severe when it occurs but in most cases you cannot tell the APSC and binned UHD apart in conditions of good light.

other side by side of a dpreview sample shot cropped again there is moire in their situation on the full frame but in effect the image quality is identical.

So personally am not going to bother with APSC unless I need more magnification and I am not in low light. For all the rest I will use full frame binned.

ProRes RAW

The A1 also provides its pixel binning mode in ProRes RAW and it is identical to the internal recording when the lens corrections are off. ProRes RAW does not have a concept of lens profile so you get all the lovely defect of your lens. To my horror e-mount leses have many defects, all are distorted and have significant amount of CA.

ProRes RAW vs Internal

In short unless you have a DSLR adapted lens with zero defects those aberrations are troublesome so with native glass am skipping ProRes RAW altogether.

4K with External Recorders

If you have a Ninja consistent to what Gerald Undone says you can get a scaled down version of 8K setting your HDMI output to Auto or 2160. Auto generates 4k60fps while 2160 gives you the same frame rate of your 8K.

Interestingly if you do not record to card the HDMI output goes back to what you get in internal recording. So in short you need to record 8K to card which means eventually overheating. It is unclear what subsampling is being output howeverthe image does look a bit cleaner.

8K vs 4K

There is no doubt that the 8K mode although only available up to 30 fps is superior however editing the 580 mbps HEVC files is not that easy.

I personally shoot in 4K so I am set on the full frame binned 4K but if you have the hardware to process and the screen to watch 8K is the way forward. Gerald Undone trick of the HDMI 4K while shooting also works but be careful with overheating.

Coming Soon

Next article will break down the codecs available with the A1.

Sony A1 : The One or Two Face?

I have been looking for a camera that would be a significant upgrade from my GH5M2 for some time and I have narrowed my options to two choices: the Sony A1 and the Canon R5. As the A1 underwater port system can use most of my glass I have recently acquired the A1.

Did I get the upgrade I was looking for? For photos I would say the answer has been an immediate yes due to the amazing autofocus and EVF of this camera and the burst rate. For me 15 fps is enough but the fact the A1 can trigger a flash with electronic shutter at 1/200 of a second is amazing. But I still like the mechanical shutter (unlike the Z9) and this goes to 1/400 which is also a first.

Let’s have a look at the A1 and where it stands at the end of 2022.

The Sony A1 was announced in January 2021 and was at that time the fastest, high resolution (>42 MP) full frame camera on the market. 

Capable of producing 20 fps continuous autofocus at staggering 50MP and 30 fps JPEG it still is the full frame camera producing the highest resolution at the highest frame rate as the Nikon Z9 has the same frame rate but lower sensor resolution.

As new cameras have come along we have seen some development especially on the video front and while the Sony A1 can produce ProRes RAW this is at half resolution (4230×2430) the Canon R5 is able to output 8192 x 4320.

Users have been curious on why the Canon R5 can do that while the A1 can’t and also why does the Z9 produce ProRes RAW internally at half resolution, so similar to the A1 and NRAW (that is likely not RAW) at full resolution?

Various tests on video show that both the Z9 and A1 outperform the Canon R5 in video on all formats.

Interestingly SNR improves 0.8 stops moving from 8K to 4K full frame which would not be possible if the camera was skipping pixels.

But of course neither the Z9 nor A1 can produce external ProRes RAW 8K and users have been screaming at Sony. 

Investigations

I was quite suspicious of the fact that the Z9 can only record internal raw and I have noted that Nikon has pushed back on RED lawsuit on RAW recording and therefore I believe NRAW is actually demosaiced.

I looked at dpreview studio scene and compared those cameras and in addition added also the Panasonic SR1 to check the image quality.

You can see how all cameras are affected by false color artefacts, the A1 and Z9 much more than others.

Moire is not an issue

The other suspicious fact is that the A1 and Z9 produce ProRes RAW at half resolution. How can the camera produce RAW at half resolution with no false colour artefacts if the 2×2 cell is made of different colours?

If you follow mobile phone technology, you are familiar with the super high resolution claim of certain phones, this article on Sony semiconductors web page provides an insight

The actual pixels are arranged in cells of 4 of the same colour and to produce the high resolution image the pixels are re-mosaiced, which in turn could produce artefacts. This technology has been mainstream for at least 4 years.

If you look at this video you can see that ProRes RAW video no longer produces false colour artefacts but is prone to moire as the camera does not have a low pass filter.

Dpreview studio scene provides some additional insight looking at video grabs.

No false color in 4k video

Moire in 4k video due to low resolution generating aliasing

My conclusion is that the A1 as well as the Z9 are cheating. Unlike the Canon R5 they are based on a quad-bayer sensor cell and therefore will not offer the same color resolution at 1:1 pixel of the canon R5.

It has already been proven that the A7S3 has a quad bayer cell.

Measures like DxOMark color depth do not look at color errors so this will not be spotted but I believe the remosaic of pixels of the same colour is the issue here that is showing in the dpreview studio scene.

There has been additional debate then on why the A1 defaults to APSC mode when producing 4K video, this is counterintuitive however the APSC image does not have moire nor false colour.

If we carry on with the assumption that what I have written here is correct, we can have a look at the required bandwidth to read the sensor and produce video output at various resolution and frame rates

HVDepthFPSBandwidthRGB BandwidthSubsampled
86404860123015.11654445.34963222.674816
57603240126013.43692840.31078426.873856
4320243012607.55827222.67481615.116544
384021601212011.94393635.83180823.887872
28801620121206.71846420.15539213.436928
Bandwidth Gbps for various video resolutions

Considering a readout at 12 bits we can see that the highest bandwidth is for the 8K and the 4k APSC mode as the other modes have less pixels even the 120 fps does not get to that bandwidth however required a faster sensor scan and is cropped

When the raw data goes in the image pipeline it is converted into RGB signal and here we can see that after subsampling the ASPC format has the highest data volume due to the 422 subsampling.

This in turn produces the least artefacts in fact it is quite resistant to moire as anti aliasing can be performed in camera using different techniques. So this is why APSC footage from the A1 is smoother but not necessarily sharper in fact the opposite.

A different current of thought may say no it is a full resolution classic bayer filter array which is then binned for 4k video however

  1. Such technology does not exist is not advertised there are no patents
  2. The remosaic of quad bayer sensor has been mainstream in mobile phones for years now and is done on chip

So my take is Sony is just leveraging mobile phone technology for the IMX610 in the A1 but I am open to the challenge.

For clarity as some readers seem not to understand I believe the camera has a total of 50 megapixels arranged in a quad bayer cell and goes to 12.5 in video 4K full frame combining pixels in 2×2 cells. There are phones on the market with 108 megapixels so this is nothing new.

The A1 is produced on the Exmor RS line which has been developed for mobile technology so no suprise the same investement is leveraged for cameras.

Many commercially available phones already implement the same features of the A1 see for example the specs of the Xiaomi12

Video Format Choice

The other question is then what to shoot now that we know or think we know the inner workings of the camera?

  1. 8K suffers from similar false colour artefacts of still images and 8k displays are rare it is only available in 4:2:0 subsampling due to bandwidth issues.
  2. APSC is cropped while the image has no defect this mode does not have a benefit on other cameras like the Panasonic GH6, it also does not support 120fps. Many other cameras offer cropped APSC 4k footage: you do not need an A1 if you want APSC video.
  3. UHD has moire in certain situations due to the lower resolution being out resolved by the lenses used and the lack of anti aliasing filter however it does offer the highest dynamic range and no false colour artefacts

My approach is to use UHD and if I have moire, use APSC. Moire is visible in the EVF so you can then mitigate it by switching to APSC only when required.

I have done a full analysis of the codecs and frames which I will post in a later article.

The other consideration is that I did not get a full frame camera to shoot it in APSC and in fact the A1 APSC also looks the same as my Panasonic GH5M2 and offers minimal benefit of DR and SNR due to the smaller size of the cropped area.

Now that I know (or think I know!) What may be behind the A1 limitations, am I disappointed? Actually I am not. I did not buy this camera for 8K, I have no ability to edit or display 8k but I wanted an upgrade to 4k and I can say the A1 holds video footage at 12800 ISO in slog3. I have yet to see any moire and prores raw 4k@60 is amazing quality, surely there is distortion and chromatic aberrations and vignetting but especially underwater or topside long lens this is not an issue. I am a bit disappointed by the codecs on card especially as HEVC does not have a 30 fps mode however overall the camera delivers an extremely pleasing image quality in 4K with outstanding clean colours using slog3/cine.gamut. If there is one thing that is weak is the IBIS.

If you are a purist and want the best image quality in full sensor should you look at the canon R5? This is where it gets interesting. I believe the R5 has a cleaner image however Canon is behind in terms of sensor technology so at the end when you look at real life images in terms of IQ and SNR I do not see the Canon taking an edge. What the Canon is better at is ergonomics, menu systems but not ultimately image quality despite all the things discussed here.

Conclusion

Despite all the cheating the A1 remains an amazing camera, it is small, it has many lens options and has the best underwater ports option and I do not regret my choice in fact I look forward to using this underwater. And finally, all of this just made me reflect on what a great camera the Panasonic GH5M2 is and I will keep it for some time until I am happy with all use cases.