Critic Wanted

[Rezn8]

Canon EOS60Da , Canon 300mm F4, CGEM Mount, 12 x 3min, 200ISO, Suburbs.

[Rezn8]

M42

[jnc71106]

looks ok but i'd say you have clipped the black point and lost the finer detail

[Cath]

A nice image Rez

It's heavily black clipped though. This is shown by all the flat black area in this view point of your image ..

[sologuitarist61]

That is really very good through a camera lens, though the processing needs looking at.

[Velvet]

not bad with camera but as said before processing just needs a little look at. Most think background should be really black

but not always the case as details can be lost in acheiving this.

Velvet

[jon1000]

Looks very nice to me, wish I could take an image like this.

[msh1]

A nice image Rez

It's heavily black clipped though. This is shown by all the flat black area in this view point of your image ..

cath what software do you use to get that 3d effect

mark

[allcart]

In order to give genuine honest critique , it is absolutely vital that I am familiar with the equipment used to take the image in question. I must know thw capabilities and limitations of the imaging device.

I therefore respectfully request that you send your 60Da to me for evaluation purpose. A couple of months of use should be enough.

[Rezn8]

Thanks everyone for your comments. Could someone briefly explain what / how clipping the black point is ?

[Cath]

cath what software do you use to get that 3d effect

mark

Hi Mark

It's just a bit of test software I've done for myself. Just allows me to see the results of some other software I'm writing.

[Cath]

Thanks everyone for your comments. Could someone briefly explain what / how clipping the black point is ?

When you clip the black level you are removing data/info from the dark areas of the image by making them too dark. When you make them too dark the near-black pixel intensity levels go below zero intensity, and so are then lost because when you save your image to a file it has to remove any pixel intensity levels that fall below zero (for your average image file format that is).

The result is what you see in the image I posted, all the black areas have lost all their data due to it having to be removed because it was below the zero intensity level.

[msh1]

Hi Mark

It's just a bit of test software I've done for myself. Just allows me to see the results of some other software I'm writing.

ah i see i could have used that ah well never mind thanks anyway

[ollypenrice]

This is a demo I use;

The quick way to test the RGB background is to open curves and Alt CLick on the background. A better way is to have the colour sampler active in three locations. Preferences vary from a starting point of equality in three channels. Some go for significantly higher blue, some for a point or two more red, etc. I try to stay at or above 23 except for obscuring dust such as seen in dark nebulae.

Olly

[Rezn8]

Thanks for the info. Very helpfull advice.

[Rezn8]

Same stack, just did simple streching . Better blacks ? Any other recomendations on processing needed please ?

[ollypenrice]

Yes, better. Now try to balance the colours by lining up the top left of the histogram peak in each colour channel, thus;

I've arrowed the red channel to show the point that should line up on each channel. You can only do this by clipping back so ideally do it at each iteration of Levels to avoid black clipping.

Olly

[Jessun]

Rezn8, that was a leap in the right direction .

It's a very nice image, 'safe' framing, some nice star colour and fine detail in the nebula. It is still one notch too dark, you'll see how the right side of the image is on the brink of being all black. The problem is that once clipped, the data is gone, and you can't go back and correct. As Olly noted the colours aren't quite aligned.

I had a play with your image, and tried to lift the dark a bit and get more depth in the nebula. What happens then is that it becomes noisy, and the best remedy is more subs. Double what you have and it should make a big difference in how the faint parts will come out.

The core - Trapezium - is for most a case of taking a set of shorter exposures and layer that in.

/Jesper

[martin_h]

Yes, better. Now try to balance the colours by lining up the top left of the histogram peak in each colour channel, thus;

I've arrowed the red channel to show the point that should line up on each channel. You can only do this by clipping back so ideally do it at each iteration of Levels to avoid black clipping.

Olly

As per Ollies post, but I set the little dropdown box in the histogram to "Colours", the histogram then becomes semi transparent and coloured ....makes it easier to see the overlaps....

[Rezn8]

Thanks for all the info. I thought I had aligned channels in DSS. Can changing the background sky levels, or playing with levels put the colour channels out of sync ? Also, does the above mean that your background of nebulae and galaxies , would/should never be black ? Always containing some nebulosity ?

[martin_h]

Thanks for all the info. I thought I had aligned channels in DSS. Can changing the background sky levels, or playing with levels put the colour channels out of sync ? Also, does the above mean that your background of nebulae and galaxies , would/should never be black ? Always containing some nebulosity ?

Black - ish, dead sharp black usually means you have clipped the data somewhere, It doesn't always contain nebulosity....only if its there in the first place.

Aligning channels in DSS will help, but as you stretch the image the channels can become misaligned, usually because one channel being stronger than the other two.