600 F5.6 DO

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H2ODoctor
H2ODoctor Regular Member • Posts: 319
600 F5.6 DO

.As a bird photographer, I wish Canon would make a 600mm F.6 DO.  Looking at Nikon PF 500; the size and weight are fantastic.  It is <10 inches and a shade over 3#s.  How heavy would you expect a 600 F5.6 DO to be?  4#s? 4.5 #s?

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quiquae Senior Member • Posts: 1,905
Re: 600 F5.6 DO
2

H2ODoctor wrote:

.As a bird photographer, I wish Canon would make a 600mm F.6 DO. Looking at Nikon PF 500; the size and weight are fantastic. It is <10 inches and a shade over 3#s. How heavy would you expect a 600 F5.6 DO to be? 4#s? 4.5 #s?

A 600mm F5.6 would have an entrance pupil with an area 1.56x larger than a 500mm F5.6. (PF/DO helps with the length of the lens, but not the diameter; if you want a smaller front diameter, the only way to do that is to raise the F number.)

Assuming that a) the mass of any given lens element is going to be roughly proportional to its area, and b) the mass of the entire lens is proportional to the mass of the front element, we would expect such a lens to be on the order of 1.56x as heavy as that Nikon @ 1460g, which means 2277g (5.0 lb). That's light, but not quite as light as you may have hoped. I suspect an actual specimen would be a bit heavier, as even DO requires the body to be longer as the focal length increases, which will increase the mass of the lens barrel more than just in proportion to the front element size.

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Steve Balcombe Forum Pro • Posts: 13,833
Re: 600 F5.6 DO

quiquae wrote:

Assuming that a) the mass of any given lens element is going to be roughly proportional to its area, and b) the mass of the entire lens is proportional to the mass of the front element, we would expect such a lens to be on the order of 1.56x as heavy as that Nikon @ 1460g, which means 2277g (5.0 lb). That's light, but not quite as light as you may have hoped.

I think you're probably being unduly pessimistic. The Tamron 150-600 zooms weigh around 2 kg, and they are only 1/3 stop slower. Remove all the zoom lens complexity, then use a DO element and the same light weight design and construction as the 600/4L IS III, and you will surely be around 1700-1800 g max.

quiquae Senior Member • Posts: 1,905
Re: 600 F5.6 DO
2

Steve Balcombe wrote:

quiquae wrote:

Assuming that a) the mass of any given lens element is going to be roughly proportional to its area, and b) the mass of the entire lens is proportional to the mass of the front element, we would expect such a lens to be on the order of 1.56x as heavy as that Nikon @ 1460g, which means 2277g (5.0 lb). That's light, but not quite as light as you may have hoped.

I think you're probably being unduly pessimistic. The Tamron 150-600 zooms weigh around 2 kg, and they are only 1/3 stop slower. Remove all the zoom lens complexity, then use a DO element and the same light weight design and construction as the 600/4L IS III, and you will surely be around 1700-1800 g max.

Being "only" 1/3 stop slower results in 21% less surface area. There is a good reason why Canon is aggressively slowing down consumer grade RF lenses--huge wins in cost and handling in proportion to the loss of light.

As another reference point, EF 400mm F4 DO IS II is 2100g. According to my mass ~ front element surface area hypothesis, a 600mm F5.6 would be 15% heavier than 400mm F4, or 2415g (5.3 lb). So we're still in the general neighborhood of my previous guess, and nowhere near 1700-1800g.

Mind you, I wish I am wrong and you are right--I don't like heavy lenses. But I am not optimistic.

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BirdShooter7 Veteran Member • Posts: 5,199
Re: 600 F5.6 DO

Yes that would be a very interesting lens.

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BirdShooter7 Veteran Member • Posts: 5,199
Re: 600 F5.6 DO

If it’s 5lb I’d be very happy, if they could do even lighter, even happier!

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H2ODoctor
OP H2ODoctor Regular Member • Posts: 319
Re: 600 F5.6 DO
1

I think Canon could sell a lot of them if the weight were ~5 #s.  I also appreciate that the DO lenses are much shorter.  Makes it easier to take on a plane.

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Steve Balcombe Forum Pro • Posts: 13,833
Re: 600 F5.6 DO

quiquae wrote:

Steve Balcombe wrote:

quiquae wrote:

Assuming that a) the mass of any given lens element is going to be roughly proportional to its area, and b) the mass of the entire lens is proportional to the mass of the front element, we would expect such a lens to be on the order of 1.56x as heavy as that Nikon @ 1460g, which means 2277g (5.0 lb). That's light, but not quite as light as you may have hoped.

I think you're probably being unduly pessimistic. The Tamron 150-600 zooms weigh around 2 kg, and they are only 1/3 stop slower. Remove all the zoom lens complexity, then use a DO element and the same light weight design and construction as the 600/4L IS III, and you will surely be around 1700-1800 g max.

Being "only" 1/3 stop slower results in 21% less surface area. There is a good reason why Canon is aggressively slowing down consumer grade RF lenses--huge wins in cost and handling in proportion to the loss of light.

As another reference point, EF 400mm F4 DO IS II is 2100g. According to my mass ~ front element surface area hypothesis, a 600mm F5.6 would be 15% heavier than 400mm F4, or 2415g (5.3 lb). So we're still in the general neighborhood of my previous guess, and nowhere near 1700-1800g.

Look at it another way - the 600 III is f/4 and 3050g, so how much lighter would an f/5.6 (50% less area) be? It wouldn't be half the weight of course, but we still have the trump card - DO...

Mind you, I wish I am wrong and you are right--I don't like heavy lenses. But I am not optimistic.

Me too - I don't think we will ever be able to learn the answer by weighing an actual RF 600/5.6 DO

Dave
Dave Veteran Member • Posts: 5,356
Re: 600 F5.6 DO
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Plan B a EF 400mm F4 DO IS II and a 1.4x EX III?

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H2ODoctor
OP H2ODoctor Regular Member • Posts: 319
Re: 600 F5.6 DO

I agree that is the best option now. However, a 600 DO would give even more reach. With a 1.4X, I could get to 840 mm and a 2X would give 1,200 for perched birds although I don’t imagine I would do that very often due Lack of light.

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AKRover Regular Member • Posts: 223
Re: 600 F5.6 DO

H2ODoctor wrote:

I agree that is the best option now. However, a 600 DO would give even more reach. With a 1.4X, I could get to 840 mm and a 2X would give 1,200 for perched birds although I don’t imagine I would do that very often due Lack of light.

The amount of detail a lens delivers depends on its diameter, not its focal length. Focal length only determines how many pixels we get to keep when cropping to the AOV we desire, but we have remarkable pixel density. I can (and sometimes do) crop my 400DO to 2200mm with 5.4 megapixels on my M6II using only a 1.4X.  This ability to crop effectively turns my lens into a 900-2200f/9-22 zoom lens.  I could put a 2X on and get to the same 2200 with 10.8 megapixels, but I don’t really need that many pixels for small bird images and I would lose the option of shooting 900 without cropping. Your 600 proposal would get me to 2350 at 5.3 megapixels using the lens bare, or 10.6 megapixels with the 1.4X, or 21.2 megapixels with the 2X, but it really doesn’t let me go any tighter on the AOV because diffraction limits the amount of detail. In all of the crops described above, diffraction will look like f/22 equivalent (my personal limit for the purposes of calculations). 2350 is 7% more reach than the existing 400 DO’s 2200, but it would come at the expense of a physically much longer lens and the loss of f/4 as an option. That existing 400 DO is a nice compact way of getting 100mm of usable aperture (considerably better than Nikon’s 89mm 500PF). Is there a compelling case for Canon to give us 7% more reach in a less portable package? I don’t see it. A 500f/4 DO with 25% more aperture would certainly be more interesting.

Don't make the mistake of thinking sensor size has anything to do with reach.  Sensor size is essentially the limit on your widest AOV for your lens, not the tightest.  This all comes down to pixel density and aperture diameter.  Answer two questions for yourself and the calculations become easy.  How many pixels do you really need?  How much diffraction can you tolerate (I even shot a bird feather in studio while varying f-number)?  If you really think you would love a 600f/5.6, the 400 DO II already exists and is awesome.

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H2ODoctor
OP H2ODoctor Regular Member • Posts: 319
Re: 600 F5.6 DO

Can you share an example of this with your M6II?

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CanonKen Senior Member • Posts: 2,918
You will have to make due with 600mm f/11 it looks like!

Agree something like you explained would be great.  However, it seems once you breach the 100mm front element (600/5.6 would be roughly 110mm) the costs spiral for the branded lenses.  500mm f/5.6 puts you at about 90mm.  I'd be happy for Canon to copy Nikon!

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AKRover Regular Member • Posts: 223
Re: 600 F5.6 DO

H2ODoctor wrote:

Can you share an example of this with your M6II?

This one is roughly 2000mm equivalent as cropped and thus f/20 equivalent

Juvenile Pie-billed Grebe

This one is only about 1300mm equivalent and it is a reduced size but it still somewhat shows the idea

Black-throated Blue Warbler

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AKRover Regular Member • Posts: 223
Re: 600 F5.6 DO

One more in between at about 1700mm equivalent (f/17 equivalent), this one at full size

Cooper's Hawk

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AKRover Regular Member • Posts: 223
Re: 600 F5.6 DO

I forgot this extreme one of a bird I rarely encounter so I take what I can get.  This is cropped to 2700f/27 (!) with a noise equivalence of ISO 23,000 (FF equivalence) and only 3.8 megapixels left out of 32.  This is going too far in all categories by my usual limits (f/22, ISO 16,000, and 4 megapixels), but it is actually still very usable for smaller display sizes.  Imagine a half page in a small bird book, for example.  The goal in the field is always to get as close as possible as this would look much better at 900f/9 with an ISO of about 2500, but when I can't get close, the 400 DO is still very good, well, to 2200 anyway.  We all have to decide what we can and can't use.  This one is going in my collection, but I certainly don't consider it a great image.  It is just a good example for this thread showing what happens when we really push.

Scarlet Tanager

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H2ODoctor
OP H2ODoctor Regular Member • Posts: 319
Re: 600 F5.6 DO

I know how to calculate the effective focal length when cropping but am unaware of how to calculate the effective F value.  Please share that information with me.

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AKRover Regular Member • Posts: 223
Re: 600 F5.6 DO

H2ODoctor wrote:

I know how to calculate the effective focal length when cropping but am unaware of how to calculate the effective F value. Please share that information with me.

If you calculated a 'focal length multiplier' when calculating equivalent focal length, then equivalent f-number is actual f-number times focal length multiplier.  Another way, the easy way with a 100mm aperture diameter, is that equivalent f-number is equivalent focal length divided by actual aperture diameter.

Noise gets visually multiplied, too, when cropping so I always calculate a noise equivalence in terms of full frame ISO.  For that calculation, you have to square the focal length multiplier and multiply by the actual ISO used.  I find calculating equivalence for my crops to be helpful in understanding the barely acceptable images.  Sometimes it isn't just one thing that went wrong, it is everything.

I was moving a bit too fast yesterday so my numbers were actually wrong on two of the images.  I shoot almost every single shot with the 1.4X and with the aperture wide open so I completely missed the fact that I must have bumped the aperture dial for that grebe as it was shot at f/6.3 which means the crop has diffraction equivalent to f/22, not f/20.  The hawk was shot without the 1.4X (I should have remembered the scramble to remove it) so it is actually only about 1200f/12 equivalent.

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Steve Balcombe Forum Pro • Posts: 13,833
Re: 600 F5.6 DO

H2ODoctor wrote:

I know how to calculate the effective focal length when cropping but am unaware of how to calculate the effective F value. Please share that information with me.

The way to understand this is:

For reasons we don't need to explain here, if the aperture of a lens is expressed as "focal-length-divided-by-<whatever>", e.g. "f/4", then the brightness of the image it creates will be the same for any focal length. So far so good, that's well known.

But what if we crop the image? Let's say by a factor of 1.6. The equivalent focal length is multiplied by 1.6 (that much you already understand) so to maintain the brightness we also have to multiply the f-number by 1.6. Writing it as an equation, we could say:

f/4 = (f x 1.6) / (4 x 1.6)

So the equivalent f-number is 4 x 1.6 = 6.4. We normally take the nearest standard value so f/6.3.

Another way to arrive at the same result is to increase the f-number by the necessary number of stops, if you know the value. In the case of a Canon sensor with a crop factor of 1.6, it's always approximately 1 1/3 stops, so f/4 -> f/5.6 -> f/6.3. This is really handy for a simple full frame vs crop sensor calculation, but for arbitrary amount of crop as in the discussion we're coming from, multiplying by the crop factor is easier. So for a crop factor of 3.3 (chosen completely arbitrarily), f/4 is equivalent to f/(4 x 3.3) = f/13.2 - we'd say f/13.

arbitrage Regular Member • Posts: 458
Re: 600 F5.6 DO

H2ODoctor wrote:

.As a bird photographer, I wish Canon would make a 600mm F.6 DO. Looking at Nikon PF 500; the size and weight are fantastic. It is <10 inches and a shade over 3#s. How heavy would you expect a 600 F5.6 DO to be? 4#s? 4.5 #s?

This doesn't help with the weight guessing but Nikon did file a 600 f/5.6 PF patent at the same time as the 500PF and it was a 5cm longer lens. So that would be a good estimate for the length. Also the front element of 110mm...1cm wider than the 400DOII and the same as the 300/2.8.

The actual length in the patents will be longer than the physical lens as they are measured to the sensor plane.  But the 5cm difference would hold true relative to the know physical length of the 500PF.

https://nikonrumors.com/2018/02/01/the-latest-nikon-patents-400mm-500mm-and-600mm-f-5-6-phase-fresnel-pf-lenses.aspx/

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