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  #1  
Old 18-05-2018, 03:34 PM
Startrek (Martin)
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Canon 600D vs Canon 7D mark 11

I am currently using a Canon 600D at prime focus for imaging and was interested in seeing the comparison of this 8 year old camera to the most recent series Canon 7D mark 11

Both have APS-C sensors ( 600D 18 megapixel and 7D11 20.2 megapixel )

Apparently the 7D mark 11 has extremely low noise at high ISO where the 600D suffers at higher ISO

Does anyone have any experience with the Canon 7D mark 11 ??

I may consider upgrading early next year but want to keep using DSLR until I feel the need to go CCD

Thanks in advance

PS: my 600D is stock ( no mods )
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  #2  
Old 18-05-2018, 03:57 PM
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gregbradley
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https://www.dpreview.com/reviews/ima...44578503921836

Canon 7Dii is $2398 at Digidirect.
Canon 80D is $1498

Canon 6Dii is $2405

Canon 6D is $1777 (slightly better dynamic range than the latest 6Dii. Only advantage of the 6Dii for nightscapes is the variable tilt LCD screen.


Then there is the Nikon d750 (aging but a good performer)
Nikon D810 also a good performer.

You can get full frame sensor cameras for the price of the 7Dii. 7Dii is supposed to have very low read noise. But it must have other components that are somewhat noisy as the DPR studio scene looks fairly clean but not impressive.

Full frame sensors are 1 stop more sensitive to light than APSc due to the collection size of the larger sensor. They typically have 1 stop better dynamic range as well and have a wider field of view for the same focal length.

600D is several models ago whereas 7D2 is the current model.

Greg.
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  #3  
Old 18-05-2018, 04:25 PM
JA
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If it has to be Canon then the Canon 6D is the better choice, if you are happy to work with fullframe. As Greg said the 6D has lower noise than the more recent model, the 6D mkII in images and is far ahead of its APSc Canon brothers old and new, in terms of noise. This performance difference becomes even more pronounced as ISO rises.

All of the Nikon choices mentioned by Greg are also excellent. I would also add the Nikon D600 and Nikon D610, both very quiet/as quiet as the others. Then there is Sony too.

Best
JA

Last edited by JA; 18-05-2018 at 05:46 PM.
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  #4  
Old 18-05-2018, 06:27 PM
Startrek (Martin)
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Thanks for the replies

The cameras you both mentioned are full frame

I was told to use crop frame not full frame DSLR for my 6” f6 reflector on a HEQ5 mount

Any advantages using full frame ?? I know full frame are substantially more expensive than crop frame ( that would not be an issue for me )

I image everything I can find including Lunar, planets and up to mag 7 DSO’s

I welcome any comments / advice with respect to full frame vs crop frame

Thanks
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  #5  
Old 18-05-2018, 06:52 PM
JA
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Hi Martin,

As an answer to Fullframe v APSc and what differences you can expect, take a look at the images below as a guide to the differences you can expect in noise and image quality. The images are a tiny excerpt from the DPReview test scence.

The first image is from 4 Canon cameras (2 FF, 2 APSc) Canon 6D, 6DMk2, 7D, 7DMk2 in their standard studio lighting. There is unfortunately no specific image for the Canon 600D; however, it uses the same sensor and processor as the 7D so should be the same, certainly no better as the 7D was a higher end model.

The second image is for the same 4 Canon Cameras, except that the lighting is very low in comparison and typical of the challenges you might expect in night street shooting, i.e: the closest thing readily available as an immediate standardised comparison to the ultralow lighting challenge of astrophotography.

I've set the ISO to 3200 even though one probably wouldn't shoot that high, as a sort of indication of what could be expected post processing after a few stops of stretching the exposure.

You will have a smaller field of view with the APSc camera. a factor of 1.6x smaller for Canon.

Best
JA
Attached Thumbnails
Click for full-size image (Canon 6D v 6DMk2 v 7D or 600D v 7DMk2 - STD Lighting.jpg)
145.4 KB22 views
Click for full-size image (Canon 6D v 6DMk2 v 7D or 600D v 7DMk2 - LOW Lighting.jpg)
130.7 KB11 views

Last edited by JA; 18-05-2018 at 08:41 PM.
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  #6  
Old 18-05-2018, 07:59 PM
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billdan (Bill)
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Hi Martin,

If you were told to only use an APSc camera, maybe your plumbing (i.e. focuser barrel diameter) is too narrow.

The converging light beam as it approaches the chip is dependent on your focal ratio (f6). A full frame (36x24mm) sensor has a diagonal measurement of 44mm. So if you want to fully illuminate that sensor then the focuser barrel must be wide enough to achieve this.

Going from the sensor towards the objective, the light cone increases by distance divided by focal ratio. So at 30mm from the sensor the light cone has increased by 5mm or is now 49mm wide, at 60mm its 54mm wide and at 90mm its 59mm wide. As you can see a 2inch (50mm) focuser will severely cut off that light cone. With an APSc sensor of 30mm diagonal at a distance of 90mm away the light cone is 45mm wide, well within a 2inch focuser barrel.

To be safe you should have a 3 inch (75mm) focuser for a full frame camera, it all depends on how much vignetting you are willing to live with.

Cheers
Bill
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  #7  
Old 18-05-2018, 11:20 PM
Startrek (Martin)
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Hi Bill,

Your explanation makes perfect sense, the sensor area has to match your telescopes optical system at prime focus, most importantly the focuser barrel

My focuser has a 2” barrel and therefore a full frame sensor would probably be to large

If I were to upgrade my 600D at some stage in the near future then the obvious choices from the current series of high end Canon APS-C would be either the 80D or the 7D mark 2

The 600D has worked very well for me , just finished 3 hours of imaging on a cold but clear night in Sydney. Took some really clean images of Jupiter at 70 deg at ISO 200 and 400

Thanks again for all the replies, very informative and helpful I must say

Good evening
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  #8  
Old 03-06-2018, 09:41 AM
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I had a Takahashi FS152 scope with a 2.7 inch focuser.

When I went to a full frame sized Astro camera (SBIG STL11) I found it would vignette terribly. Also with the 2.7 inch reducers.

I went to 4 inch and it was fine. My TEC180 had a 3.5 inch focuser and that was fine even with a 16803 sensor which is larger than full frame.

I am not sure what size is the minimum for full frame but estimate it could be 3 inches.

Greg.
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