[wildman]

Thanks guys.

Actually I'm not just making small talk.

I'm seriously considering buying a dedicated body to be permanently mounted on the back end of my 560mm APO triplet.
Considering it's magnification and its relatively slow (f/7.1) I need excellent ISO performance. But I also need resolution
for cropping. Most birds are only about the half the size of my fist and even at 560mm they often need some cropping
Especially with a full frame.

At this point the A7r looks like a good balance between ISO performance and resolution for my purposes. Time will tell.

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Last edited by wildman; 08-02-2014 at 01:37 PM.

[normhead]

What pray tell, is a 560mm APO triplet?

[rawr]

so far as noise is concerned

The DxO low-light score isn't just about noise, as your own examination of their formula shows. It's about DR too, and about reading the curves as much as looking at the final numbers. Like Rondec I find their scoring system conservative, but still useful. It gives me a good guidepoint for working with the cameras I have.

Unfortunately the character and quality of the visible noise generated by a sensor - including chroma and colour noise, and banding noise - doesn't feature directly in the DxOMark assessment. Even if they had the same DxOMark low-light score, Camera A may make a real mess of high ISO, with smudgy clumpy noise - or even worse, banding - that is ugly and difficult to clean up, but Camera B may produce high ISO images that merely look flat and lifeless - so may need some post-processing to revive them - but otherwise are pretty clean.

[wildman]

What pray tell, is a 560mm APO triplet?

It's a scope rather than a conventional telephoto.

Thanks guys.

Actually I'm not just making small talk.

I'm seriously considering buying a dedicated body to be permanently mounted on the back end of my 560mm APO triplet.
Considering it's magnification and its relatively slow (f/7.1) I need excellent ISO performance. But I also need resolution
for cropping. Most birds are only about the half the size of my fist and even at 560mm they often need some cropping
Especially with a full frame.

At this point the A7r looks like a good balance between ISO performance and resolution for my purposes. Time will tell.

Don't know about the A7r. I do know a little about SNR and consequences, mostly from Clarkvision.com . I went to K5 bodies in 2011 for dance, especially in theater. 2.8 & 1600 or 4 & 3200 is my starting point because I'm stopping motion with constant light sources at typically, 1/320. As the in house photographer for a local ballet conservatory, I shoot a lot of dance. Went to K5IIs bodies for the better low light AF plus my K5's had a lot of use.

I always shoot DNG. Even with portrait sessions, I don't worry about ISO 1600. Shot a few images in a headshot session today with just the modeling lamp and 1600 looks great at 100%.
K20's, 800 was the limit, without PP work.

With a K5IIs, 3200 just means my default ACR settings are at 50% for luminance reduction. If I'm printing. I will use Noiseware at defaults and printing large, maybe some handwork. It does depend on the image. Hard stage light is amenable, scenes with analogous colors are tough,beginning with AF, just no contrast. Performance photos, I'll got to 6400 or 12,800 if needed. They do get bought and printed. Not scientific but it works.

[normhead]

It's a scope rather than a conventional telephoto.

How accurate is your AF confirmation going to be? That's a consideration. 7.3 on a 2.8 focusing system could be a little problematic. But you can always ignore confirmation and just focus on what looks right, I do that with my A-400 and 1.7 TC all the time. However, you would be reducing your level of magnification going to an FF system rather than an APS-c. So you're scope would be roughly equivalent to less than 400 mm on APS-c and you can buy an A-400 5.6 for about $500. Without going into a lot of detail, that's not a lot of reach for birding.

The birding guys I see using FF are shooting at least 600mm. The Nikon guys are using the 600 ƒ4. Speed and reach in a very heavy $15k package. If you want cheap reach, why not one of the Canon point and shoots with the 30x or higher zooms. My birder buddy, who's interested in ID but not necessarily IQ uses one. Or for slightly better quality, but lot more money, a Q with and adapter for a 55-300. ƒ7.3 is not going to produce the shutter speeds you need for birding, 90% of the time.

How about one of these?
CANON POWERSHOT SX700HS BLACK 16.1MP 30X W/CASE 9338B015

IN any case, I'm fascinated by your way of achieving reach, let me know how it turns out. My A-400 and 1.7 TC gives me 560 mm, or roughly equivalent to 840 FF, @ƒ 9.3. having enough light to have a high shutter speed is an issue for sure, but it can be done, as long as the birds are co-operative about only hanging out in bright sunlight.

[wildman]

How accurate is your AF confirmation going to be?

I'm going out the door right now will get back to you later...

...in the mean time here's a few links to my work. It's old stuff and not my best but you can get an idea:


https://www.pentaxforums.com/forums/122-lens-clubs/55946-300mm-plus-lens-club...ml#post2890202
https://www.pentaxforums.com/forums/122-lens-clubs/55946-300mm-plus-lens-club...ml#post2894668
https://www.pentaxforums.com/forums/122-lens-clubs/55946-300mm-plus-lens-club...ml#post2890534
https://www.pentaxforums.com/forums/122-lens-clubs/55946-300mm-plus-lens-club...ml#post2890237

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Last edited by wildman; 08-03-2014 at 02:41 PM.

[wildman]

How accurate is your AF confirmation going to be?

Never rely on it - I'm old school and grew up using the ground glass screen of a Rollei F. I'm fine with trusting my eye.

you would be reducing your level of magnification going to an FF system rather than an APS-c.

Yes I thought of that. Even with a crop sensor I often have to crop. So I thought perhaps a modern full frame with it's superior resolution and ISO performance might more than make up for that.
But your point is well taken. Failing that I might try the Sony a6000 on the scope. Light, fast and cheap and I'm fascinated by the idea of a mirror-less camera.

The birding guys I see using FF are shooting at least 600mm. The Nikon guys are using the 600 ƒ4. Speed and reach in a very heavy $15k package.

I once had a chance to use the scope and the Canon 600mm on a FF Canon. For sheer raw on axis resolution the scope was obviously Superior. Pushing light through three very highly corrected high quality elements at prime focus (nothing between the subject and sensor but the three elements compared to the 16 elements on the Canon) is, I think, about the same problem a 16 element zoom has compared to a seven element prime. In any case it was clear what I preferred. What others use is their business.

why not one of the Canon point and shoots with the 30x or higher zooms.

Because the sensor can't deliver the high quality RAW data I require - at least not yet. I rely on my PP skills at least as much as my gear to give me the final results I want.

[Fogel70]

OK...

... so given all that, comparing the k5 to the Sony A7s, 3702/1162 = approximately a 3 stop advantage of the Sony over the K5.

Thus K5@ISO 800 = A7s@ISO 6400 so far as noise is concerned.
Does that sound about right in the real world?

I'm using an ISO of 800 as my standard reference because, based on my experience on the K5, unless I'm doing some extreme cropping there is usually no significant practical difference from IS0 80-800 when using the full frame. So for normal shooting I'm fine with an ISO of 800 or below when using the K5.

Your calculation is incorrect. 3x as high ISO is ~1.5 stops. So ISO 800 on K3 would be similar to ISO 2400 on A7s.
One stop is 2x, two stops 4x, three stops 8x.

Edit:
I attached an example from dpreview comparison tool, but the only have ISO in full stops, but it's easy to see that A7s has a bit more noise @ ISO 3200 than K3 has at ISO 800 when viewing images at the same magnification.

[wildman]

So ISO 800 on K3 would be similar to ISO 2400 on A7s

1.5 stops - significant but, perhaps, not worth 2500 bucks especially considering the APS-C sensor on the K3 might allow for better and less cropping.
Also, given this, the A7r would probably be no better than approximately 1 stop.

Given this I'm back to considering the Sony a6000 as the best bet over the K5 for my bird work. Also the Sony would be very versatile for other uses.
Other then that I could soldier on with the K5 - not a bad option either.

Thanks for the correction.

[normhead]

1.5 stops - significant but, perhaps, not worth 2500 bucks especially considering the APS-C sensor on the K3 might allow for better and less cropping.
Also, given this, the A7r would probably be no better than approximately 1 stop.

Given this I'm back to considering the Sony a6000 as the best bet over the K5 for my bird work. Also the Sony would be very versatile for other uses.
Other then that I could soldier on with the K5 - not a bad option either.

Thanks for the correction.

Certainly, there's nothing wrong with your results....

The sensor utilizes a gapless on-chip lens design, which fills the gaps between neighboring pixels with optimized lenses that match the angle of incidence to increase light gathering ability and produce edge-to-edge sharpness and quality.

There's a caveat in there on the low light optimization. I'd be writing to them, saying I might buy your camera if you tell me what lenses might work well with it. Without that info it's just marketing hype.

DxO gave the A6000 the exact same rating it gave your K-5,

[Winder]

Just trying to wrap my head around what all this means in practical real world terms.

Put it this way -

given two cameras with an ISO rating one of 1000 and one of 2000.
All else being equal does this mean a gain of 1 stop in ISO performance for instance?

So at an ISO rating of 1000 you have a certain level of noise, say X, at an ISO of 800 and at that
same level of noise on the camera with a ISO rating of 2000, all else being equal,
you have the same level of noise (X) at ISO 1600?

In other words:
DXO ISO rating of 1000 = X@ISO 800
DXO ISO rating of 2000 = X@ISO 1600

And DXO defines X as a SNR of at least 30db at a DR of 9EVs at 18bits.

Just trying to translate this rating into something more useful and intuitive.

There is more to it than that. If you have two cameras that have nearly identical S/N ratios and the same size sensor like the Canon 5D original and the A900, but different pixel count the camera with more pixels will produce better images. The same applies to the K-5 and the K-3. The K-3 is producing better prints because the noise that is present is a very fine grain. The K-5IIs has a high-ISO score of 1216 while the K-3 has a high ISO score of 1208. The K-3 has less color blotching and the noise has a finer grain to it which makes it less noticeable. I find the K-3 noise cleans up with minimal processing. I'm finding that I often don't need any Luminance NR at ISOs where I previously would have used it. Setting color NR to 25 in LR is usually all I need. If the image need a lot of work I send it through DxO Prime NR which does a great job, but is painfully slow.

Two cameras can have identical S/N ratios or DxO high ISO scores and still produce visible different IQ.

[Rondec]

1.5 stops - significant but, perhaps, not worth 2500 bucks especially considering the APS-C sensor on the K3 might allow for better and less cropping.
Also, given this, the A7r would probably be no better than approximately 1 stop.

Given this I'm back to considering the Sony a6000 as the best bet over the K5 for my bird work. Also the Sony would be very versatile for other uses.
Other then that I could soldier on with the K5 - not a bad option either.

Thanks for the correction.

I do wonder if you wouldn't do well with a K3 at this point, unless you are averse to going on with a k mount camera. Basically same low light score as K5, but more pixels. For wildlife, seems like it would work pretty well. I think that is what Dane.Dawg uses primarily at this point.

[wildman]

One stop is 2x, two stops 4x, three stops 8x.

Yep - spot on. I had forgotten that f stops are on a log not linear scale
Thus, using the DXO ISO scores, a camera having a 3 stop ISO advantage over the K5 would require a DSO ISO rating of over 8000 - a rating no camera comes close to.

two cameras that have nearly identical S/N ratios and the same size sensor like the Canon 5D original and the A900, but different pixel count the camera with more pixels will produce better images.

Hadn't thought about that - All else being equal pixel density may have an effect on perceived noise.

I do wonder if you wouldn't do well with a K3 at this point,

So do I.

The simple way out would be a K3. However something like the a6000 has advantages over a DSLR that intrigue me - the idea that a camera may work as well, if not better, on my bird shots as the k5 and also be a fast, responsive, light and small walk around is very compelling. I still pine for my 1950s era Nikon S2 rangefinder. The possibility of a digital S2 gets my attention.

I think I'll wait and see how prices go in the near future - it isn't as if the k5 is hopelessly outdated yet.

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Thanks everyone for your input it's been helpful.