Large spot on my sensor

pointshooter

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Legend has it that everyone in the world will eventually pass through Times Square in New York and Trafalgar Square in London. Likewise, every amateur photographer will one day erect a tripod and shoot the moon. Ah, the ubiquitous moon shot (actually a class assignment). Details below.





Camera: T2i (550D)

Lens: EF 75 to 300 mm, sans IS. As we were recently advised here, you have to be “out of your mind” to buy this lens. I saw it for $149 a few months ago, case included, and, well, perhaps the advice has merit, and senility or dementia is finally setting in. Not sure if IS would have helped anyway, after all, the earth kept spinning under my feet and the moon may have moved a tad. At 300 mm (480 mm on a crop body), you have to keep recomposing every few seconds.

File format: RAW
Focal length: 300 mm (480 mm)
Mode: Manual
Shutter: 1/80 sec
Aperture: f/11
ISO: 100

White balance: Auto. Should I have used ‘shade’ for the twilight on earth or ‘daylight’ for the moon? :) It was a chilly night, and I preferred the warm glow the shade setting provided.

Yes, it was cropped. The moon only fills about 15% the width of the frame at 480 mm.

Post-processing:

1. DPP – cropped to 624 x 935 pixels (2:3), adjusted white balance and saved three TIFs at EV +2, 0, and -2.

2. Photomatix – input EVs above and saved as fused using 0 and -2 EVs.

3. GIMP – rescaled to 2000 x 3000 pixels, unsharp mask, removed some slight chromatic aberation around the moon’s horizon. Found a great GIMP plug-in for this at http://photocomix-resources.deviantart.com/art/Fix-Cromatic-Aberration-95683614 , saved result to JPG.

Observations: It won’t be used by NASA on a future landing, but it makes a nice 4 x 6 print. This is also where the flip-out screen on the T3i would have been a big advantage for live view and tripod work – particularly those of us on the cusp of infirmity.

Best to all.
--
Editor Bob
 
This is my moon, couple of nights ago ;)

Lots of cropping, originally shot with the Sigma 50-200mm f:4-5.6 OS HSM. Just tweaked WB and sharpening on Lightroom. Nothing else.





--
Martin Ocando
-------------------------

 
Did you rotate yours 90-degrees clockwise? On mine the 'terminator' is just about vertical. If not, it's fascinating how the perspective changes with latitude. Mine was taken on 10/5.
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Editor Bob
 
Did you rotate yours 90-degrees clockwise? On mine the 'terminator' is just about vertical. If not, it's fascinating how the perspective changes with latitude. Mine was taken on 10/5.
This 'rotation' continuously changes as the moon rises and sets.

Depending on the latitude this can be up to 180 degrees (e.g. near the equator). At the pole, the perceived rotation of the terminator is at a minimum.

... However sometimes you need to rotate the camera to fit the moon on the sensor!





Regards

Andy.
 
Nope. I was dark top light down, I just rotated it a bit to look for a pleasing angle. Since you don't have anything else in the frame, just rotate by taste.
Did you rotate yours 90-degrees clockwise? On mine the 'terminator' is just about vertical. If not, it's fascinating how the perspective changes with latitude. Mine was taken on 10/5.
--
Editor Bob
--
Martin Ocando
-------------------------

 
Excellent detail. I see dimples in many of the craters. Note that you took it at 50 mm. Maybe I am going about this the wrong way. I'm having trouble maintaining focus at 300 mm.

--
Editor Bob
 
Why do you have trouble maintaining focus. Does the zoom move on it's own? My old 75-300 does and it would have to be secured with tape ot when pointed up, it will retract. Once the focus is set, it won't need to be changed unless you change the amount of zoom. I use a T3i and shoot from a tripod with the image stabilization turned off. It is difficult to keep the moon in the frame for vary long since it does move, especially when viewing it at 10X in the LCD to manually focus. You may have better results stopping down to f/8 to f/11 at 300mm. I use manual mode and set the aperture where it is the sharpest, lock the ISO to 100 (usually) and vary the shutter speed to set the exposure. Also, use a remote switch or the 10 second timer.

There is one I took earlier this week with Tamron 70-300 VC plus a Kenko MC4 2.0X DGX teleconverter shot in raw. This is at full size and I pasted in the EXIF info into the shot.



--
Tymevest
 
Why do you have trouble maintaining focus. Does the zoom move on it's own? My old 75-300 does and it would have to be secured with tape ot when pointed up, it will retract.
My 75-300 is fairly new. I have not noticed zoom or focus creep. It just seems very sensitive - just a tad shake and it's out of focus. I have tried both manual and auto focus.
You may have better results stopping down to f/8 to f/11 at 300mm.
My shot was f/11 at 1/80 second.
I use manual mode and set the aperture where it is the sharpest, lock the ISO to 100 (usually) and vary the shutter speed to set the exposure.
Yes
Also, use a remote switch ...
Yes.

It would seem to me at a distance of 240,000 miles, you could just bang the focus ring up against infinity and be there. I guess in terms of space, that is not infinity, and also not for the lens.

Anyway the hunk of green cheese should be making its appearance at this hour, so I might try some more.

Best to all.

--
Editor Bob
 
[snip]... Note that you took it at 50 mm.
Hi, Sorry for the delay...

The shot was taken using 2000mm. (Not 50mm)

(I used a chipped adapter that fools the camera into thinking a 50mm lens is attached, this allows AF detection to work with a telescope - Although I find manually focusing with Liveview at 10x mag is more reliable)
Maybe I am going about this the wrong way. I'm having trouble maintaining focus at 300 mm.
Can you expand on this...
What do you mean by maintaining focus ?

I would always use a good stable tripod.

Try using Manual focus with liveview and 10x magnification enabled.

Take your time and very carefully adjust the focus until the image is very sharp on the LCD. (If there is a dead spot where fine focus adjustment makes no difference - then set the focus to the middle of this position)

When shooting, use the 10 second self timer, if you do not have a remote release.

Try raising the ISO (200 or 400) to increase the shutter speed. It may help.

Also watch out for atmospheric turbulence. If the image is quivering like a jelly when there is no wind and tripod vibrations have died down, then try a different location or a different night. (calm cool nights away from any built up area is best)
It would seem to me at a distance of 240,000 miles, you could just bang the focus ring up against infinity and be there.
No - these days this is rarely the case, most lenses will focus past infinity. This ensures that infinity focus can be achieved at all temperatures and zoom settings.
I guess in terms of space, that is not infinity, and also not for the lens.
As far as your lens is concerned, anything past about 1 mile away will be so close to the true infinity position, that you would not be able to tell any difference.

Regards

Andy.
 
Andy,

Thanks for the response and tips on moon shooting.
(I used a chipped adapter that fools the camera into thinking a 50mm lens is attached, this allows AF detection to work with a telescope - Although I find manually focusing with Liveview at 10x mag is more reliable)
Maybe I am going about this the wrong way. I'm having trouble maintaining focus at 300 mm.
Can you expand on this...
What do you mean by maintaining focus ?
The EF 75-300 mm lens focus is extremely sensitive in the manual mode. I did use the 10x magnification in live view, but just didn't seem to be able to nail itl
I would always use a good stable tripod.
Did that.
Try using Manual focus with liveview and 10x magnification enabled.
Did that.
Take your time and very carefully adjust the focus until the image is very sharp on the LCD. (If there is a dead spot where fine focus adjustment makes no difference - then set the focus to the middle of this position)

When shooting, use the 10 second self timer, if you do not have a remote release.
Did that.
Try raising the ISO (200 or 400) to increase the shutter speed. It may help.
I kept the ISO at 100 to minimize noise and the aperture at f/11. Even so, I was taking shots at 1/160 sec.
Also watch out for atmospheric turbulence. If the image is quivering like a jelly when there is no wind and tripod vibrations have died down, then try a different location or a different night. (calm cool nights away from any built up area is best)
Yes, I considered this as a possible limitation.
It would seem to me at a distance of 240,000 miles, you could just bang the focus ring up against infinity and be there.
No - these days this is rarely the case, most lenses will focus past infinity. This ensures that infinity focus can be achieved at all temperatures and zoom settings.
I guess in terms of space, that is not infinity, and also not for the lens.
As far as your lens is concerned, anything past about 1 mile away will be so close to the true infinity position, that you would not be able to tell any difference.
I would have thought that at a range that close to infinity and with an aperture of f/11, focus would not have been that much of a problem.

Perhaps I'm at the limits of my equipment. As I have said, the results still make for a nice 4 x 6 print or wallpaper on the monitor. Anyway, it's been fun and I plan to keep trying.

Thanks again.
--
Editor Bob
 
The EF 75-300 mm lens focus is extremely sensitive in the manual mode. I did use the 10x magnification in live view, but just didn't seem to be able to nail it
This is a common problem with some lenses - The focus thread is too course. It's great for macro and 'fast focus', but not so good for fine work :-(

One possible thing that could be tried, is to fashion a lever to give you better control.

Another method is AF - Select the centre AF point and try placing it over a cratered area of the moon. Take a shot at a time and if the focus is good, then switch to MF to lock the focus.
I kept the ISO at 100 to minimize noise and the aperture at f/11. Even so, I was taking shots at 1/160 sec.
Apart from reducing shake, a higher shutter speed can also help to freeze (and hence reduce) the atmospheric turbulence.

One other problem I've had, is shutter vibration (not mirror - that was locked up!) causing image blur. I found it best to shoot from liveview mode.

In other words don't focus and then exit from liveview, before taking the shots.

Noise is a tricky thing to reduce as its dependant on sensor temperature, ISO setting and underexposure, but I've always found that a little noise is much better than vibration. Each setup is different and obviously you have to find the best compromise. However I've never found noise to be excessive at 400 ISO on my 400/450D.

Sure it's visible, but noise can be removed almost entirely at these levels with some PP.

With regards to heat build up and liveview... What I tend to do is MF focus the lens and then turn the camera off for 5 mins or so, to let the sensor cool down. I found this reduced the noise by a factor of 2 compared to 'just leaving it in liveview all the time'.
Perhaps I'm at the limits of my equipment. As I have said, the results still make for a nice 4 x 6 print or wallpaper on the monitor. Anyway, it's been fun and I plan to keep trying.
The next step (once you get the sharpest images you can) is to try stacking the images. Adding them together reduces the noise even further (i.e. 4 images equal half the noise, 9 images equal one third etc...)

You can then use heavy amounts on unsharp mask (at various radius) to bring out the fine detail without the noise dominating the final result.

I have used various software packages for stacking 'Astrostack' and 'Deep Sky Stacker' spring to mind.

Regards

Andy.
 
Andy,

Sounds like you have been 'around the block' with this sort of thing. I have tried most of the more obvious things you have suggested.

One problem is evaluating what I am getting while shooting. The T2i doesn't have a flip out live-view screen. Even at 10x magnification it is hard to crouch down to see what I am getting. What looks good in playback just doesn't hold up when I get it downloaded.

Thought I had a decent tripod, but adjusting a focus ring at the end of a somewhat long lens at 300 mm (480 mm) creates a lot of leverage (no IS capability).

Sensor heat should not be a problem, as I usually leave the camera in review for a while checking out each shot. Not sure whether this leaves the sensor on (live-view) or not.

As indicated in the original post, Photomatix was used in PP, but with 3 different EVs from the same shot.

Finally, I'm just not sure of what to expect. My first post is about as good as it gets.

My best.
--
Editor Bob
 
One problem is evaluating what I am getting while shooting. The T2i doesn't have a flip out live-view screen. Even at 10x magnification it is hard to crouch down to see what I am getting. What looks good in playback just doesn't hold up when I get it downloaded.
Correct me if I am wrong... But I think the T2i has a much higher resolution LCD screen than my 450D. Some time ago I remember calculating the resolution was sufficient on a 500/550D for a true 1:1 at 10x mag. (Not possible on my 450D - so I have to guess best focus somewhat!)

I fully understand the pain in the neck when shooting straight up... and it's a catch 22, because if you fully extend the tripod it's unstable as a jelly!

One tip here is to use a mirror to reflect the LCD image to a more convenient angle. This can be either taped to the tripod, or if you are keen a small bracket can be made up to hold the mirror in place.

A small magnifying glass in the hand may help you to see the finer details on the LCD.
Thought I had a decent tripod, but adjusting a focus ring at the end of a somewhat long lens at 300 mm (480 mm) creates a lot of leverage
Very true!
Sensor heat should not be a problem, as I usually leave the camera in review for a while checking out each shot. Not sure whether this leaves the sensor on (live-view) or not.
I don't know the answer to that, however if the LCD lamp heats up the camera though, it probably does not help much.
Finally, I'm just not sure of what to expect. My first post is about as good as it gets.
It may be that you have reached the limit of that lens. If that's the case, it all gets rather expensive to go further. As a longer lens or telescope is the next step.

Unfortunately this only makes it harder, as the atmosphere / vibration problems only get worse!

Regards

Andy.
 
Ok. Finally got a good clear night last night. So here's mine.





Pushing the 350D (Rebel XT) sensor to the limit but not bad for a 6 year old 8Mpx body Sigma 100-300 at 300mm, 100% crop with a little levels adjustment and some USM sharpening.

Ian
 

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