[Ghillie]

Can someone recommend a free software that I can use to examine individual pixels of a digital photograph? The simpler and easier to use the program is, the better.

Thank you.

Tom

[photoptimist]

What do you mean "examine individual pixels?" Almost any image viewer can zoom in to 400% or more to magnify the pixels.

[Ghillie]

I shot some photos of Mercury with a 200 mm lens and a 500 mm lens, using white light solar filters. I can't find Mercury in any of the images. At around nine arc seconds, I expect it only darkened a few pixels on my K5. I would like to delve into the images and try to determine if Mercury was imaged.

[pschlute]

I shot some photos of Mercury with a 200 mm lens and a 500 mm lens, using white light solar filters. I can't find Mercury in any of the images. At around nine arc seconds, I expect it only darkened a few pixels on my K5. I would like to delve into the images and try to determine if Mercury was imaged.

Any decent software will be able to view your image at over 100% (which means 1 pixel in your image = 1 pixel on your screen). But the more you zoom the more you just end up with a blocky mush.

Post your picture.

[AstroDave]

How sharp is the edge of the sun in your pictures? i.e. how much smear (for lack of a better term due to seeing and or focus effects)

Your 200mm lens has a scale of about 5 arceseconds per pixel on the K5 - so Mercury will be less than 2 pixels wide!

At 500mm, you are more like 2 arcsec per pixel - so Mercury might be 4 or 5 pixels across. Unless your images are that sharp, you won't see much more than a smear of somewhat darker pixels.

For more on K5 camera pixel scales, check this post: K5 Scale Factor - Arcseconds per pixel for several lenses - PentaxForums.com

arcsec/pixel will scale as the inverse of focal length

If you want to estimate it yourself for various lenses, look at How to make an a priori estimate of camera image scale, in arcseconds per pixel - PentaxForums.com

And to actually measure it, try this: Easy Determinations of Camera Scale Factors (arcseconds per pixel) - PentaxForums.com

(I called that "easy" but it is a bit detailed!)

[Not a Number]

What photo editor are you using now? Just playing with the brightness/contrast curves could bring the image out.

[AstroDave]

And here is my best shot of the transit, with Mercury near the edge of the sun. This is a 100% crop - i.e. every pixel is there. Try zooming in on this with, say, Photoshop, to see how fuzzy it is.

This was with my DA* 300mm lens and 2X and 1.7X teleconvertors on a K3 - a focal length of 1020 mm (twice that of your 500mm) and about 25% more pixels.

Depending on how you count, Mercury is only 8-10 pixels across here.

Attached Images

View Picture EXIF

File Date

 

[biz-engineer]

I'd use a macro lens with an extension tube to photographs individual pixels.

[Bob 256]

Astro Dave is right-on. If you were out of focus just a bit, Mercury won't show much at all since it's just a pin-prick against the solar disc.

As for pixel examining free-ware, Irfanview is one which has a lot of functionality, but if you can't see Mercury with the sun shown full frame (say in a 5x7 print), chances are, you won't find it by looking any closer.

https://www.irfanview.com/

[Ghillie]

Hello Folks,

Thank you for your help. I downloaded and installed Irfanview, and it is a nice program. But at 500x I couldn't see any darkening in the images. I guess I must have been out of focus, or maybe my lenses just aren't up to the task. I've attached one of the best images I got that day, if anyone would be so kind as to take a look.

Thanks, Tom

[AstroDave]

I guess I must have been out of focus

Hard to tell from this image - the pixels have been averaged. But the edge of the sun is not very sharp.

Can you give us a cut-out of the edge of the sun, with no pixel averaging?

There are other problems here, too. The sun is overexposed, which will tend to wash out any "blemishes" in front of the sun itself. All that fogging around the sun should not be there for a proper exposure - the background should be BLACK!

What solar filter were you using? It may be too much! (And, could also be the cause of the fogging around the sun.) You've got the ISO cranked way up to 3200. Your aperture is 5.6, which is probably wide-open for the lens, whereas f/8 or f/11 would almost certainly give sharper images.

Before the next solar event (Eclipse 2024?), I suggest you experiment with solar imaging - it should be easy to use ISO 100, f/8 or f/11, and shutter speed in the 1/2000 to 1/4000 second range. Note the exposure in my EXIF data above. This image was taken with a ND 3.0 filter - exposure factor of about 10 stops, and 2X and 1.7 X teleconvertors - f-stop losses of about 3.5 stops. So, my total filtration was 13-14 stops. If you have a polarizer, that will knock off another stop.

Also, practice focus. If your lens is autofocus, it can probably focus on the edge of the sun. But otherwise, you will want to practice manual focusing.

[Ghillie]

Hi Dave,

The filter is from Thousand Oaks.

I think I need to change my equipment to make it more accessible. It is very awkward for me to make any adjustments, especially focus. I'm cobbling together two tripods to get the height I need to see the back of the camera. I have a strong tendency to move inadvertently and nudge the tripod. So overall, I have a lot of thinking to do. Here are a couple of photos of me, so you can see what I'm up against.

Thanks, Tom