Red Cat 250mm F4.9 lens -- big claims, pretty big price

VidThreeNorth · Feb 24, 2019

"‘World’s sharpest’ 250mm lens now on Kickstarter with swappable lens mount" Published Feb 20, 2019, DPreview.com, Daimien Demolder
"https://www.dpreview.com/news/82579...-lens-now-on-kickstarter-with-swappable-mount"

"Taiwanese lens manufacturer William Optics is proposing to make a flatfield Petzval lens aimed at star gazers and photographers that it claims is the world’s sharpest 250mm."

I'm not deeply into astronomy or astrophotography, so there are specs that I do not understand, but the overall claim is that this is the sharpest lens of its kind, and the regular price of ~$700 US is not cheap either. When used as a camera lens, this is a "T-Mount" fully manual lens. At this point, it is not clear to me whether the mount adapters include an aperture -- probably not, though you could create your own apertures to be used by inserting them into the internal filter mount. At 225mm x 80mm it is not really that small, and 1.47 kg is not that light, and F4.9 is not that bright. And the 44mm coverage is barely enough for full-frame (APS-C is a safer bet if you don't want vignetting). So, it better be really sharp. But then, that's what they are claiming, so . . . .

First deliveries are expected March 2019.

Braineack · Feb 24, 2019

cool. a huge, bulky, manual focus lens with a less-than-useful focal length and aperture... don't sign me up.

480sparky · Feb 24, 2019

48mm filter? Gimme a break.

Braineack · Feb 24, 2019

is 250mm even a common star-gazer focal length?

snowbear · Feb 24, 2019

Braineack said:
cool. a huge, bulky, manual focus lens with a less-than-useful focal length and aperture... don't sign me up.

But it's red and has a kitty lens cap!

Braineack · Feb 24, 2019

not going to lie, that almost got me. if it was pink instead of red, id be preordering today.

480sparky · Feb 24, 2019

I want blue. Dark blue.

VidThreeNorth · Mar 1, 2019

Braineack said:
is 250mm even a common star-gazer focal length?

I was wondering about that too. I did some cursory research and this appears to be the situation:

Telescopes:

Telescopes closest to the Red Cat 250mm tend to be a bit larger and longer. The more typical sizes are ~350mm and ~400mm, and longer, and they generally come with tripods. If they are apochromatic (like the Red Cat) the total package will cost more, and yes, they will be larger. Also, I didn't see mention of Flourite lenses, and since such a lens is expensive, I think a manufacturer would say so.

In all, I think the normal price is probably fair enough. But as said before, it depends on the actual performance.

Photographic Lenses:

Now here I was disappointed. Again, 250mm F4.9 does not even exist. I think 300mm is close enough to compare, and they have long been available at F4.0. But B&H only listed 2 of them. I know that there are a few others probably still in catalogues, but B&H does not even list them as orderable.

The listed lenses included a Micro 4:3 lens by Olympus, which of course is fully auto exposure/focus, and the one Full Frame by Nikon "Nikon AF-S NIKKOR 300mm f/4D IF-ED Lens", which is likewise fully auto exposure/focus and is relatively a bargain at $1,149 US, but again, about 50% more than the
Red Cat. The Olympus' lower field (coverage) makes the comparison weak. Then again, a 200mm F4 on an APS-C camera is equivalent to 300mm, and 150mm on Micro 4:3 is also equivalent to 300mm. But that is not the end of the story.

First, there are a few zooms that cover 250 - 300mm, which are not going to be as sharp, and will cost more than the Red Cat.

Second, there are the "catadioptic" (mirror based lenses) 300mm APS-C lenses around. I thought it was odd that the "Red Cat" lens was fully refractive (not a "cat"). But anyway, there are a few of the "cats" around, and they are not that expensive ($260 US range). But the standard warning is that the out of focus ("bokeh") is going to be odd because speculars have "holes" in them. If you have a lot of out of focus speculars they are going to look like a bowl full of Cherrios.

Some people really dislike that. I would agree if the artistic value of a picture is important. If you are just "recording data" (ie: I saw this bird at 18:00 . . . .), then it won't be important. But I think most of prefer our pictures to look the best that they can.

I'm generally artistically fairly open minded, but I don't know how I'd react to seeing 20 pictures in a row that look like that. I was surprised that there does not seem to be a Full Frame cat lens. Cats were around back when 35mm SLRs were around, so it would not even be a new idea.

I can also add that I recall, years ago, that there was a an eyepiece adapter to use long photographic lenses as telescopes, so they could work both ways, if someone is still doing that.

But the result is that again, the Red Cat is currently unique, and if the lens proves to be that good, I would call it a "fair" price.

Edward56 · Nov 22, 2019

I wanna Dark blue

photoflyer · Nov 22, 2019

Here is an in depth review. If you do astrophotography, this may me be for you, depending on what you are after.

Derrel · Nov 22, 2019

I think the 250 mm focal length would be useful for some things .

Sometimes seemingly slight difference in focal length can be quite beneficial good for example a 45 mm lens is quite different from a 50mm, and a 58mm or 60mm allows you to make photos that are quite a bit different than a 50 millimeter lens.

In the telephoto arena the Nikon 180 mm was quite a popular lens in the 1980s, and I still own one from that decade, and I own a much newer AF-D model, and having it be slightly shorter than a 200mm is often times of great benefit.

Over the decades I have owned several 300 mm prime lenses most recently the 300mn f/4 AF-S and the 300mm f/2.8 AF-S Mark II, the one with the magnesium barrel components and the super-close minimum focusing distance. With today's high resolution sensors there has never been a better time for a lens that is a little bit wider in angle of View... we can now crop quite heavily, with 36 million pixels or more, and still end up with a decent photo.

If this lens is as good as I think it might be its apochromatic correction might lead to really good results. Beginning around 200 mm, apochromatic telephoto lens designs begin to pay off and a 250m might be a really good APO lens to have.

480sparky · Nov 22, 2019

Derrel said:
I think the 250 mm focal length would be useful for some things .

Sometimes seemingly slight difference in focal length can be quite beneficial good for example a 45 mm lens is quite different from a 50mm, and a 58mm or 60mm allows you to make photos that are quite a bit different than a 50 millimeter lens.

In the telephoto arena the Nikon 180 mm was quite a popular lens in the 1980s, and I still own one from that decade, and I own a much newer AF-D model, and having it be slightly shorter than a 200mm is often times of great benefit.

Over the decades I have owned several 300 mm prime lenses most recently the 300mn f/4 AF-S and the 300mm f/2.8 AF-S Mark II, the one with the magnesium barrel components and the super-close minimum focusing distance. With today's high resolution sensors there has never been a better time for a lens that is a little bit wider in angle of View... we can now crop quite heavily, with 36 million pixels or more, and still end up with a decent photo.

If this lens is as good as I think it might be its apochromatic correction might lead to really good results. Beginning around 200 mm, apochromatic telephoto lens designs begin to pay off and a 250m might be a really good APO lens to have.

Back in the 80s, I was shooting with a Pentax ME Super and MX. I opted for the 120/2.8 over the 135/3.5 for three reasons. 1) almost a full stop more max aperture 2) used the same 49mm filters which my 20, 28, 40, and two 50mm lenses used as well and 3) much smaller and lighter than the 135.

Derrel · Nov 23, 2019

A 120 mm f/ 2.8 sounds like a great alternative to a 135 mm f/3.5! I have found that I take a lot of photos with my 70-200 or 70-300 lenses at around 119 to 123 to mm. Back around 1985 I bought an MX body and a complete kit of adapted screw mount lenses For around $200. I really liked the MX body, and a couple of college newspapers that I worked for had ME Super cameras as part of their pool equipment.

I am really wondering what the heck the Red Cat people were thinking about when they decided to put a 48 mm drop in filter into their lens design. Talk about the dumb move of the century in lens design. While there are 48 mm filters, both 46 mm and 49 mm are vastly more common. 46 used to be relatively common in video camera lenses, and has been used for a number of years in quite a few Rangefinder lenses , especially those made by Leica, and 49 mm has been used in hundreds of lenses by many,many manufacturers, but 48? Whaaaaaaaat?

VidThreeNorth · Nov 23, 2019

That video is just in time for the holiday spending season. A Red Cat and a Canon EOS Ra would make a nice combination. You'd want a good tripod with a tracking head, and if you don't live in a good area, a plane ticket to somewhere else.