topic Re: Iso limit 60d in EOS DSLR & Mirrorless Cameras

Iso limit 60d

Tsleel2811 — Tue, 24 Jan 2017 20:18:27 GMT

I'm getting into astrophotography and I always see people shooting at iso 3200 and above. When I shoot people in a dimly lit room the noise is unacceptable even at 1600. Is there anyway to produce a good photo with a 60d at higher ISOs than 1600? Is it something in the settings? Or the exposure triangle?

Re: Iso limit 60d

ScottyP — Tue, 24 Jan 2017 20:51:20 GMT

Those sensors are not great at high ISO. Using a tripod you should be able to get a long exposure so you don't need high ISO. If you don't like star trails you can stay like 15 seconds or faster. If trails are ok you can leave open for hours.

Long exposures can also make a little noise but not as bad as high ISO, and not accompanied by loss of detail which is the other hobgobelin of high ISO.

You can can also try wider apertures to get more light.

Re: Iso limit 60d

Tsleel2811 — Tue, 24 Jan 2017 21:25:13 GMT

Thank you for the input. I'm shooting at iso 1600 with a 15 sec exposure at f2. 8. I'm trying to let in more light without getting trails because I don't live in a relatively dark area. But thank you

Re: Iso limit 60d

diverhank — Tue, 24 Jan 2017 21:58:45 GMT

@Tsleel2811 wrote:
I'm getting into astrophotography and I always see people shooting at iso 3200 and above. When I shoot people in a dimly lit room the noise is unacceptable even at 1600. Is there anyway to produce a good photo with a 60d at higher ISOs than 1600? Is it something in the settings? Or the exposure triangle?

There is no in-camera solution for high ISO except for the long exposure noise filtering option. Most people I know don't really like using it.

I don't really shoot astrophotography but have been using high ISO occasionally for birds in flight...For the 60D, 1600 is about the acceptable cutoff ISO without post processing help. With careful post processing you can get by with 3200. With some plugins like Imagenomic Noise Pro and others, you might be able to go beyond that.

@Another way to do it is to get higher end models with better ISO performance. For my 7D Mark II, I can use ISO 6400 with acceptable results (after post processing). I can go as high as 12,800 with my 5D Mark III. Below is a picture taken with the 7D Mark II @ ISO 6400... remember I use the term acceptable...not great.

Re: Iso limit 60d

Waddizzle — Wed, 25 Jan 2017 14:58:25 GMT

@Tsleel2811 wrote:
I'm getting into astrophotography and I always see people shooting at iso 3200 and above. When I shoot people in a dimly lit room the noise is unacceptable even at 1600. Is there anyway to produce a good photo with a 60d at higher ISOs than 1600? Is it something in the settings? Or the exposure triangle?

I'm not really into astrophotography, either, mostly because I live too far away from any "dark skies".

As far as your noise goes, are you familiar with photo stacking? Dark frames? One crude way to reduce sensor noise to is to take a large quantity of identical photos, then use software to align the images. Once the images are aligned, they can be combined into a single image by averaging them together. Averaging tends to cancel out random noise, in much the same way that a long exposure of a lake, beach, or a river averages out waves, making the water appear as a sheet of glass.

Re: Iso limit 60d

Tsleel2811 — Wed, 25 Jan 2017 16:23:37 GMT

I don't know what dark frames are but I'm familiar with photo stacking. What I'm looking for is to cut out extensive PP and get the best quality from one picture from a 60d. If that's not possible I'll proceed to photostacking

Re: Iso limit 60d

Waddizzle — Wed, 25 Jan 2017 17:57:14 GMT

@Tsleel2811 wrote:
I don't know what dark frames are but I'm familiar with photo stacking. What I'm looking for is to cut out extensive PP and get the best quality from one picture from a 60d. If that's not possible I'll proceed to photostacking

A dark frame would be long exposure with the lens cap in place. The captured image will noise from the sensor, which can be used to average out noise from actual images.

Re: Iso limit 60d

TCampbell — Wed, 25 Jan 2017 23:50:23 GMT

I posted a reply to your other post on astrophotography. Probably I need more info on what sort of imaging you are trying to do.

Photographing a landscape (with the night sky) is very different than photographing a deep-sky object (or even a large section of sky) with no "land" in the image.

What sort of imaging are you wanting to do?

Re: Iso limit 60d

Tsleel2811 — Thu, 26 Jan 2017 00:15:15 GMT

I'm doing landscape with the sky in the picture. I'm trying to get the most out of my intermediate camera without having to retouch too much in PP. I'm using very good lenses (24-70mmL II and 70-200mmL II) so that takes out alot of other problems that could occur. My main issue is leaving the Shutter open for too long for fear of damaging the sensor and operating at ISOs that are beyond the capabilities of the camera. Is it basically not meant to be and I have to stack photos together or can I get a good result from 1 photo?

Re: Iso limit 60d

TCampbell — Thu, 26 Jan 2017 03:57:29 GMT

To do night time landscapes the focal length of the lens limits the time of the exposure. The Earth is spinning at a rate of 15 arc-seconds of angular rotation per each second of time on the clock. If you use a very wide-angle lens, 15 arc seconds in one second is such a small amount that you'd hardly notice it until several seconds have elapse. But if you use a long focal length length (very marry field of view) than even a short exposure can be enough that the stars have moved a noticeable amount.

For a "full frame" camera you can divide 600 by the focal length of the lens to arrive at the maximum amount of time you should expose before the motion of the Earth smears the stars and they appear elongated instead of as points of light. But with an APS-C camera, you have to divide 600 by the crop factor of the lens (which is 1.6) so and that works out to 375.

So imagine if you have a 10mm lens ... that 375 ÷ 10 = 37.5 seconds. You can expose for 37.5 seconds and you wouldn't see any elongation in the stars. Some astrophotographers think that the original value of 600 is a bit too generaous and prefer to use 500 just to be extra sure there is no elongation. 500 ÷ 1.6 = 312.5 and if you had a 10mm lens that would be 31 seconds.

You have a 24-70mm lens. At the 24mm end that would be 312 ÷ 24 = 13 seconds. You might be able to cheat that up to 15 seconds. But it's not much time. Now imagine using your 70-200mm at the 200mm focal length end... that's 312.5 ÷ 200 = about 1.5 seconds... which is not nearly long enough to collect starlight.

You can quickly see why a short focal length lens helps with this sort of phototography. But even then there's the question of focal ratio. For example an f/1.4 lens collects literally four times more light than an f/2.8 lens. Suppose (hypothetically) there's a 20mm f/1.4 lens. The focal length is double a 10mm lens. So instead of 312 ÷ 10 = 31 seconds it works out to 312 ÷ 20 = 15.5 seconds. But an f/1.4 lens collects FOUR times more light per second than an f/2.8 lens. So even if we cut the exposure time in half, the fact that we gather four times more light "per second" still works out to collecting twice as much light in in 15 seconds as the f/2.8 lens can collect in 30. It's "as if" you could take a 1 minute exposure in just 30 seconds.

So while a shorter focal length is helpful... a lower focal ratio is is also helpful. Sometimes a slightly longer focal length but a substantially lower focal ratio means the lens with the lower focal ratio "wins" in the total amount of light it can collect.

You can get around this with a tracking head and you even if you want to take landscapes you could literally double the maximum exposure duration by using a tracking head at 1/2 "sidereal" rotation speed ("sidereal" speed is the rate of Earth's rotation)... so instead of 15 arc-seconds per second it runs the motor to turn the head at 7.5 arc-seconds per second. So now a 10mm lens can expose for a full minute instead of just 30 seconds.

The digital "noise" can be reduced by processing... and all astrophotography images need processing. Capturing the image is half the work, but learning to process the image is also quite a bit of work.

Re: Iso limit 60d

Tsleel2811 — Thu, 26 Jan 2017 15:55:31 GMT

I really do appreciate it. I didn't know there was so much math involved but you already did that for me. I don't think I'm going to venture out into buying a f1.4 lens I can do with star smearing. That's actually what I'm going for here. On another post it was recommended that I take multiple shots and stack them together. I think that's the way I'll go.

If u get a tracker wouldn't it smear the foreground because it's following the stars?

Re: Iso limit 60d

TCampbell — Thu, 26 Jan 2017 16:42:00 GMT

So if you WANT star trails, that's a completely different discussion.

Set your camera to shoot 30 second exposures.

Also set your camera to "continuous" drive mode (like you'd use for to burst for sports photography), get a remote (wired) shutter release because these usually have a "lock" button on the shutter. You can press and lock the shutter button on the release and it'll just keep taking photos continuously.

Then press and lock the shutter button and let the camera continuously shoot another frame every 30 seconds... and leave it going for a good long while.

You'll need a free program called StarStaX which will merge all your exposures (each of which have a short trail) so that you end up with a single merged frame that has very long trails.

This is an area where longer focal lengths actually help because it means the stars appear to move more in 30 seconds than they would in a wide angle lens.

As for the tracker...

The same rule that applies to how much something can move before you can notice it in the stars ALSO applies to the land. So without the tracker, the land doesn't move at al, but the stars move at 15 arc-seconds per second. Tha rate of 15 arc-seconds per second is also known as "sidereal" speed in astronomy (pronounced "sid" "ear" "ee" "ol").

With a tracker that can track at sidereal speed, the stars will appear to not move at all in a long exposure (assuming the tracking head was precisely polar aligned to the celestail pole).

However... if you have a tracker that can track at 1/2 sidereal speed, then the "land" will appear to move at 7.5 arc-seconds per second AND the stars will ALSO appear to move at 7.5 arc-seconds per second. But recall that at that 15 arc-seconds per second speed, we could divide 600 by the focal length of the lens to arrive at the number of seconds we can expose before we notice the blur. Well... if everything is moving half as fast (7.5 arc-seconds per second instead of 15 arc-seconds per second) then we can expose for TWICE as long (it's like dividing 1200 by the focal length instead of 600 by the focal length). BTW, that 600 is based on a full-frame camera so we still have to factor in the crop factor. But still... if you halve the apparent rate that everything seems to move then you can expose for twice as long.

This means the tracking head is even useful for night time landscapes because it can double your possible exposure duration (assuming it has a setting to rotate at 1/2 sidereal rate, but most of the trackers I know of ... including the Sky Watcher "Star Adventurer", the iOptron "Sky Tracker", and the Losmandy "Star Lapse" all have that capability.)