Camera lens question

[varshnei (Karan)]

I have a question that I'm pretty sure I know the answer to but want to check.

I'm putting together a portable setup with the (backordered) Star adventurer GTI, Asiair and the 533MC and getting some Canon EF lenses for it. Got the 135mm on its way and was thinking of a 50mm and a 85mm too (all manual lenses). The issue is that the 50mm lens isn't supposed to that good wide open at 1.8 and only gets good enough at the edges once stopped down to f/2.8 or even f/4.

But... as I'm using a full frame DSLR lens on a ZWO ASI533MC, which only has a 1" sensor, that shouldn't be an issue right - as I'd only be using the centre of the lens?

[JA]

Hello V,

Full frame lenses are designed to generate a full frame image circle of approximately 43mm in diameter. The ZWO 533 will only see the central part of that with its 11.31mm X 11.31mm sensor (16mm diagonal). Any of the edge nastiness and abberations (coma, astigmatism, field curvature, ...) generated by the lens will therefore be masked somewhat., however, depending on which "manual"lenses you are referring to, more modern lenses may have higher inherent sharpness / MTF and possibly produce a sharper image, depending on your lens choices and settings. Sometimes the difference is small, sometimes it is not.

Best
JA

[AdamJL]

Yeah I was going to say “it depends”…
It really depends on the lens. Better quality lenses are better throughout the range from centre to edges

Oh and just remember stopping down introduced lots of star spikes as light is diffracted from the “joins” of the aperture blades

[varshnei (Karan)]

Originally Posted by JA

Hello V,

Full frame lenses are designed to generate a full frame image circle of approximately 43mm in diameter. The ZWO 533 will only see the central part of that with its 11.31mm X 11.31mm sensor (16mm diagonal). Any of the edge nastiness and abberations (coma, astigmatism, field curvature, ...) generated by the lens will therefore be masked somewhat., however, depending on which "manual"lenses you are referring to, more modern lenses may have higher inherent sharpness / MTF and possibly produce a sharper image, depending on your lens choices and settings. Sometimes the difference is small, sometimes it is not.

Best
JA

Thanks! Thank makes sense. The lens I'm planning on using are the Samyang manual ones. They're pretty decent wide open but generally not that great at the edges until 2.8 or sometimes even f4.

I'll give it a shot wide open n see if I've escaped most of the edge nastiness

[OzEclipse (Joe Cali)]

Canon EF 50mm f1.8 is a pretty ordinary lens even with an APS C. Not sure if the smaller 533 frame will miss out on the coma? It digs deep into the field of an APS C 15x22mm.

[glend (Glen)]

My personal view is that it is worth buying purpose built astro lenses with ED glass and a built in field flattener. Something like the Askar FMA135. Or the 200mm version if it's in your budget.

Check them out at Testar, some are in stock.
Some of these lenses can also be used as a guide scope or visually with an eye piece adaptor.

[gregbradley]

For nightscapes the Sigma Art 14 and 28 are good.
The best lenses I have heard of are Voigtlander APO lenses. They are medium expensive - around $1000.

The older Canon 50 1.8 isn't bad and its cheap.

Canon L 24-70 F2.8 is fine.

But really Canon does not have a really good nightscape lens.

Samyang are good if you get a good copy. QC is not their strong point but from what I have read if you stick to their upper models the QC is much better.

I have a Samyang 135 F2 Canon mount and a 21mm F1.8.
The 21mm I had to open up to shift the infinity stop as the lens focus ring did not have enough travel to get to infinity focus. I fixed that but it shows the type of issue you might have.

Greg.

[Crater101 (Warren)]

I have the Canon EF 50mm f 1.2L, and it's a great little lens if you want to spend a little more. With Canon offering more support to the RF format, you can pick them up for a bit of a bargain if you shop around.


I was going to attach the tech sheet, but it's too big - outside the attachment limit. However you can find the .pdf here about halfway down the page at the Canon Australia site...


https://www.canon.com.au/camera-lens...0mm-f-1-2l-usm

[Peter Ward]

Originally Posted by gregbradley

....

But really Canon does not have a really good nightscape lens.
......

Greg.

I have the Canon EF Wide-Angle 35mm f/1.4L II USM. Some of the
sharpest camera glass I have ever used.

Not inexpensive, but certainly outperforms my (also excellent) Sigma Art lenses.

[RB (Andrew)]

Originally Posted by Peter Ward

I have the Canon EF Wide-Angle 35mm f/1.4L II USM. Some of the
sharpest camera glass I have ever used.

Not inexpensive, but certainly outperforms my (also excellent) Sigma Art lenses.

I agree Peter.
Love the 35mm L

[gregbradley]

Originally Posted by Peter Ward

I have the Canon EF Wide-Angle 35mm f/1.4L II USM. Some of the
sharpest camera glass I have ever used.

Not inexpensive, but certainly outperforms my (also excellent) Sigma Art lenses.

Is it useable though in the corners at F1.2? That would be a first if it is. Generally fast lenses are poor performers for edge stars.
Basically these lenses are designed for portraits where edge performance is not as important as a lovely background blur. Centre performance is probably great and that's where it ends.

If you are using APSc cameras that would take the pressure off.

Sigma Art lenses promise a lot but apart from one or two they also aren't that great in the corners.

F2 is about as fast as any lens I have heard of that can still be good in the corners. F2.8 to be sure.

The couple that defy that - the Art 40mm and 28mm are monsters and weigh a ton.

Voigtlander APO, Zeiss Loxia are some of the best.

Nikon has a few.

Fuji does not have any really except the 14mm F2.8.

A good nightscape lens is quite a rare animal.

Samyang have a few but they also lack character.

Greg.

[croweater (Richard)]

Originally Posted by gregbradley

Is it useable though in the corners at F1.2? That would be a first if it is. Generally fast lenses are poor performers for edge stars.
Basically these lenses are designed for portraits where edge performance is not as important as a lovely background blur. Centre performance is probably great and that's where it ends.

If you are using APSc cameras that would take the pressure off.

Sigma Art lenses promise a lot but apart from one or two they also aren't that great in the corners.

F2 is about as fast as any lens I have heard of that can still be good in the corners. F2.8 to be sure.

The couple that defy that - the Art 40mm and 28mm are monsters and weigh a ton.

Voigtlander APO, Zeiss Loxia are some of the best.

Nikon has a few.

Fuji does not have any really except the 14mm F2.8.

A good nightscape lens is quite a rare animal.

Samyang have a few but they also lack character.

Greg.

Hi Greg, I'm certainly not disputing your observations but I just wonder what you mean about a lack of character.
Cheers, Richard

[Peter Ward]

Originally Posted by gregbradley

Is it useable though in the corners at F1.2? That would be a first if it is. "......

Greg.

Very much so. But don't take my word for it.

Canon are using their new "Blue Spectrum Refractive (BR) optics in the
new LII version.....while they are not saying too much about the
new tech, it has set a new full aperture (F1.4) DXO benchmark and is apparently now the highest ranked lens at this aperture.

[gregbradley]

Originally Posted by Peter Ward

I have the Canon EF Wide-Angle 35mm f/1.4L II USM. Some of the
sharpest camera glass I have ever used.

Not inexpensive, but certainly outperforms my (also excellent) Sigma Art lenses.

Originally Posted by croweater

Hi Greg, I'm certainly not disputing your observations but I just wonder what you mean about a lack of character.
Cheers, Richard

Yes that was a bit of a vague term. I mean colour, sharpness, lack of aberrations.

Some high end lenses make an image that just has a pop and life to it that cheaper lenses don't.

Greg.

[gregbradley]

Originally Posted by Peter Ward

Very much so. But don't take my word for it.

Canon are using their new "Blue Spectrum Refractive (BR) optics in the
new LII version.....while they are not saying too much about the
new tech, it has set a new full aperture (F1.4) DXO benchmark and is apparently now the highest ranked lens at this aperture.

Sounds good. Progress.

[JA]

I don't have the Sigma Art 40mm f/1.4, but if you can tolerate its 1200g heft, based on the quantitative measurements and tests I've seen and previously reported upon, you'll be rewarded with class leading centre and edge sharpness, contrast, ultralow chromatic aberration, and great corner performance (low coma and astigmatism) in the medium wide-angle range.

See lenstip.com for data and comparisons with other lenses.

Best
JA