Nikon full frame vs Canon crop sensor

[thegableguy (Chris)]

Hi there!

Planning to get properly into AP soon (desperate for a second hand HEQ5 to come on the market; failing that I'll buy a new one in a month or so when funds are there).

When it arrives I'll be practicing with my pro Nikon bodies (D750) and lenses (24-70, 70-200). Once I get the hang of it I'll be looking at either a fast Newt or an ED80.

From what I've read, crop sensor is the way to go due to smaller, less-vignetted images, and Canons are better for modding. High ISO also seem somewhat unnecessary in the context of AP.

Does that mean I'll get better results attaching a 700d to a telescope than my D750? It's thoroughly counter-intuitive to think a $300 body is better than a $2k body, but could well be the case.

[rustigsmed (Russell)]

Hi Chris,

Canons are traditionally considered more astro friendly probably since the 20da was released. More people seem to use canons which is why you see more modified canons. I wouldn't worry too much about this unless you were planning on a professional cooling mod like done at central ds. also astro software was usually aimed at canons, now you have backyard Nikon (in addition to eos) to control your camera.

Yes APS-c chips are more friendly because they are generally less affected by the edge of the imaging circle (where things go pear shaped quickly). You can always just crop the final images of your Nikon. I probably wouldn't worry about getting a canon unless you were really pedantic about this. the other benefit of an aps c is if you are taking planetary movies, the planet will appear much smaller on the full frame. as dslr's are often used as all rounders to begin with that makes aps-c a more cost effective option.

as for $300 vs $thousands you would be surprised what image stacking astro processing can do. the more expensive ones usually do better on a single exposure (good for nightscape) but that is fairly quickly negated on deep sky stacked targets.

Russ

[raymo]

I can't add much to what Russ said, other than to say that it depends on what you mean by high ISO. Different models of DSLR seem to have
different ISO "sweet spots", and many people use their Canon 1100Ds
and 1200Ds at ISO 1600, and sometimes 3200. You will see occasional
images here taken using 6400, and very occasionally, even higher.
From following threads here, I think Nikon users seem to frequently
use around 800-1000.
raymo

[Somnium (Aidan)]

If you can't find a second hand heq5 and what a mount that will carry a good capacity why not get a second hand neq6 pro. It will be about the same as a new heq5 but can carry a much bigger ota, provided that you are ok moving around the extra weight of the mount.

[thegableguy (Chris)]

Wow, are people really using those cheap little Canons at 3200??? Would've thought they'd be grainy as hell, especially after a few long exposures when they get warm. I've been told that you're best advised keeping any camera under about 800 anyway, even the pro models.

I've read that it's much easier to remove the IR filter on Canon bodies than Nikons due to the thickness of the glass or something. I wouldn't want to do that to my Nikons - I'd get a cheap Canon purely for astrophotography.

But if there's no significant benefit to Canon (ie no difference in cost to remove IR filter), I'm probably better off getting a D3300 or something that I can use my lenses with.

Has anyone actually modified either Nikon or Canon?

[Somnium (Aidan)]

Originally Posted by thegableguy

Wow, are people really using those cheap little Canons at 3200??? Would've thought they'd be grainy as hell, especially after a few long exposures when they get warm. I've been told that you're best advised keeping any camera under about 800 anyway, even the pro models.

I've read that it's much easier to remove the IR filter on Canon bodies than Nikons due to the thickness of the glass or something. I wouldn't want to do that to my Nikons - I'd get a cheap Canon purely for astrophotography.

But if there's no significant benefit to Canon (ie no difference in cost to remove IR filter), I'm probably better off getting a D3300 or something that I can use my lenses with.

Has anyone actually modified either Nikon or Canon?

i modified my canon 600D, it wasn't too difficult. surprisingly the camera worked when i put it all back together

[thegableguy (Chris)]

And yeah, there's a lovely second hand NEQ6 for sale right now for $1400, but I'm hoping to keep it under $1200 (the price I told my somewhat unimpressed wife)...

Also, excluding OTA / camera etc, one is 25kg - fairly manageable for a brand newbie - and the other is 34kg - pretty painful. I did seriously consider it though. I've got an 8" Dob which a NEQ6 would manage nicely.

[Somnium (Aidan)]

well if you are keen let me know because my NEQ6 is gathering dust since i got my Paramount MX, I could meet half way between the 1400 and the unimpressed wife given that i live in Sydney you could inspect and pick up. But the HEQ5 will probably be all the mount you need, just another option.

[thegableguy (Chris)]

Originally Posted by Somnium

well if you are keen let me know because my NEQ6 is gathering dust since i got my Paramount MX, I could meet half way between the 1400 and the unimpressed wife given that i live in Sydney you could inspect and pick up. But the HEQ5 will probably be all the mount you need, just another option.

Ooooooh. Maybe...

We're on holidays at the moment and also waiting on a bunch of fees to come through but that may well be a deal not to miss.

Where in Sydney are you? Just liked your FB page; love the new observatory!!

[raymo]

The 1100D, 1200D, and 550D are all very quiet. I, along with plenty of
other people, do most of my imaging at 1600, finding almost no benefit
in going down to 800. In the middle of winter I use 3200, and on really cold nights sometimes 6400.
raymo

[thegableguy (Chris)]

Originally Posted by raymo

The 1100D, 1200D, and 550D are all very quiet. I, along with plenty of
other people, do most of my imaging at 1600, finding almost no benefit
in going down to 800. In the middle of winter I use 3200, and on really cold nights sometimes 6400.
raymo

Well that's good to know. I'll get away with shorter exposures to begin with, which will be handy for the totally clueles fumbling beginner I'm guaranteed to be...!

[LightningNZ (Cam)]

A high ISO doesn't mean increased sensitivity! It's just moving the histogram towards the brighter end for the same exposure time by increasig the gain to the sensor. It also comes with a reduced dynamic range in most cases.

Now in Canon sensors to date, higher ISO is handy because it helps to overcome noise prior during pixel readout. In Sony, Toshiba or Samsung sensors (Sony is used in most Nikon cameras) this isn't the case and these have very low noise that is not improved by higher gain. These sensors like the one in your D750 offer high sensitivity, low noise and high dynamic range.

In short. Stick with the D750 unless you have a real need for a second, cheaper camera.

Hope this helps,
Cam

[thegableguy (Chris)]

Originally Posted by LightningNZ

Now in Canon sensors to date, higher ISO is handy because it helps to overcome noise prior during pixel readout. In Sony, Toshiba or Samsung sensors (Sony is used in most Nikon cameras) this isn't the case and these have very low noise that is not improved by higher gain. These sensors like the one in your D750 offer high sensitivity, low noise and high dynamic range.

In short. Stick with the D750 unless you have a real need for a second, cheaper camera.

Hope this helps,
Cam

I don't understand all of that. I do know that the D750 is staggering at high ISO - I mean at 10,000 it's almost friggin noise free, it blows my mind - so I wondered how a $300 camera could possibly come close.

I also understand that it's not sensitivity, it's gain. Like a cheap amplifier, a cheap camera would add a lot more noise at low gain than an expensive one. I'm still pretty skeptical of a 100d at ISO 3200. I just can't see such a cheap thing doing well at that level. Cameras twice the price struggle above about 2500.

I was just wondering if the gains of using a crop sensor would outweigh the increase in inherent noise, especially if I aimed to keep it under ISO 800.

But you know what? You're right. I'm better off using the vastly superior sensors in my current Nikons and cropping the images. 10 megapixels is still plenty to start with - I'm not expecting to make anything print worthy for a while.

Done. No new camera required. Hooray! Thanks all.

[Camelopardalis (Dunk)]

Some of the Sony sensors used in their own cameras in addition to some of those used by Nikon and Fujifilm exhibit a property called ISO invariance. This means a shot can appear to be underexposed but when stretched it doesn't exhibit wild noise artefacts. Most traditional camera sensors (including those used by Canon) do not behave like this, and you need to expose sufficiently using the desired gain (ISO is just gain) to get the results you want. If you underexpose with one of these and then stretch, you'll also be stretching the noise and it'll look much worse than a picture from an ISO invariant sensor.

Your D750 has a sensor that is ISO invariant...I'd go with that rather than spending anything on another camera.

That's not to say you can't get great results with a lesser/cheaper camera...many of us do it just takes some road testing to understand how to achieve the best results.

[Camelopardalis (Dunk)]

Originally Posted by thegableguy

I also understand that it's not sensitivity, it's gain. Like a cheap amplifier, a cheap camera would add a lot more noise at low gain than an expensive one. I'm still pretty skeptical of a 100d at ISO 3200. I just can't see such a cheap thing doing well.

It's not quite that simple. All sensors generate noise, for the most part it's the more expensive cameras that have more sophisticated circuitry and/or software to reduce/hide the noise, where the cheaper camera are more "raw". The 100d shares its sensor with the 600d which is almost legendary in astrophotography, even though it might seem a bit long in the tooth compared to what's available now. Results with images taken on cool evenings can be excellent.

The software tools have only been available to use Nikons seriously for AP relatively recently (BackyardNikon), whereas similar tools don't exist for other brands, including Sony...you're pretty much doing it the hard way (intervalometer) with no computer control with one of those.

[thegableguy (Chris)]

Originally Posted by Camelopardalis

Some of the Sony sensors used in their own cameras in addition to some of those used by Nikon and Fujifilm exhibit a property called ISO invariance. This means a shot can appear to be underexposed but when stretched it doesn't exhibit wild noise artefacts. Most traditional camera sensors (including those used by Canon) do not behave like this, and you need to expose sufficiently using the desired gain (ISO is just gain) to get the results you want. If you underexpose with one of these and then stretch, you'll also be stretching the noise and it'll look much worse than a picture from an ISO invariant sensor.

Your D750 has a sensor that is ISO invariant...I'd go with that rather than spending anything on another camera.

That's not to say you can't get great results with a lesser/cheaper camera...many of us do it just takes some road testing to understand how to achieve the best results.

Aaaaah, okay. That's the best explanation yet. I've only ever used Nikons so maybe that's why the concept of the best ISO not necessarily being the lowest is foreign to me!

Yeah I'll have a go with what I have already - might be able to crop by less than a factor of 1.6 anyway, depending on what OTA I end up getting (once the finances recover from whatever abuse the mount wreaks).

Cheers, thanks for that.

[Camelopardalis (Dunk)]

Yeah the penalty of choosing the right ISO is essentially eliminated with an ISO invariant sensor. Note though that historically Nikon (and everyone else) had been subject to the same laws of physics as everyone else until some of the more recent models (last couple of years). Also note that the low light "superstar" Sony A7S is not strictly ISO invariant...

If I were you, I'd still experiment using a reasonable ISO such as 1600, just so you can judge when you've exposed it sufficiently from the histogram on the rear screen. You still need to gather sufficient photons for the signal to overwhelm the read noise, and the read noise of most Nikons and Sonys are comparable to Canon models. It's not a golden goose.

The great thing about a full frame sensor is you get a much bigger FOV than a crop sensor, so you've got plenty of room to crop

[raymo]

Chris, in this section, on the previous page,[date 15/2/16] you'll see two of my single frames of Eta Carina, one at ISO 3200, and one at 1600.
These were taken in Summer when the ambient temp was about
19 degrees. 1100D. Cost me $297 new with 18-55mm kit lens.
raymo