photoshop - Is it possible to re-focus (recover) an intentionally blurred image?

I have an image which I have modified through Picasa ( using Soft Focus - essentially I am making the faces blurred ).

Question is : If I upload that photo to Facebook, and a user downloads it from Facebook, is there any way they can modify the photo so that the face is in focus again?

PS: I am not doing anything mischievous - my subject is against a brick wall holding a Nikon camera, and I just want to focus on the camera strap so I've blurred everything else.

Answer

There is a technique called deconvolution which can, to some extent, recover distorted or blurred image detail.

Topaz labs have a product called InFocus which uses this sort of technique. It can sharpen certain images, but if you have blurred your faces substantially, I believe it would be beyond the ability of any tool to recover. Maybe on CSI :P

Sharpness and bokeh comparison of Nikon 50mm f/1.2, f/1.4G and f/1.8G

The contestants are Nikon 50mm f/1.2, f/1.4G and f/1.8G. The list prices are 38,550 INR, 27,990 INR and 18,000 INR respectively.

Bokeh: As with any portrait lens, I want a creamy bokeh performance when used wide open. Theoretically, as the maximum aperture increases, the bokeh effect should be more pronounced, too, if used wide open. But, how about the quality of bokeh? Is the difference at all perceivable in bare eyes? While searching for the image produced by all three lenses, I couldn't find any comparative review putting the shots taken by these lenses, side by side.

Sharpness: How do these three lenses perform in producing sharp images when used wide open? According to this review, f/1.4G performs worse than f/1.8G at least till f/5.6.

photoshop - Which checklayers are used in frequency separations?

In many high end Frequency separation tutorials they show a variety of checklayers. But finding informations about those check layers, how to set them up, how they work, what they do and what they show is quite difficult. (only thing I found is an action by fx-ray) So, here are the questions:

• when are they used?


• What help do they provide?


• How many/what different types of checklayers are commonly used?


• How to set them up properly?

Answer

Check layer is an invented term... (well almost everything we use is invented)

In some tutorials I have seen it is only an additional layer to exaggerate something you need to see.

You are full of this tools around you:

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  You use a magnifying glass to see some detail on something small.

  
  


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  You go to a better lit place to see better the color of something.

  
  

Those two examples does not modify what you are seeing, it only gives better conditions to see what it is already there.

You use this concept for example when zooming. You are not modifying anything, you are using a digital tool to see better a detail on an image.

A check layer takes that to a next step, you use a layer that does not magnify, but gives you a more contrasted view of something. Probably it is a layer that shows a specific channel, or a brighter version, etc. It is a digital magnifying-contrasting-filtering glass to enhance something you are working below.

Imagine you are working on a photo (A).

The non-destructive method to work is with adjustment layers (B) For example a dodge and burn.

And that is all happening inside your monitor (C)

The Check Layer is just this glass to enhance something you need to see better (D).

When, how many, why, what... It is up to you. If you need to see something better invent your own layer to contrast and enhance what you need to see.

The only condition is that you put this layer on top, and you only modify the layers below it.

Just two examples that have an obvious problem and an obvious thing to look for (not only for skin retouching) that come to my mind, are:

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  Dark object on dark background. You could need to contrast the difference between them, for example to prepare a mask.

  
  


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  Using one channel (for example blue) to see better a bruise on the skin.

  
  

In frequency separation one case could be enhancing the high frequency layer to actually see it. Normally it just looks as a gray flat image if you see it alone.

Am I doing something wrong or do I need a new lens? [DOF and focal length]

I'm new to photography and I can't get a nice DOF. I read up on all the technicalities that involve DOF and I still can't get it right.

For example, if you take a picture very close to an object, zoomed out, and then move further back and zoom in would the pictures show the same DOF given the aperture was adjusted?

With my kit lens (EF-S 18-55mm 1:3.5-5.6 IS) I can't change the aperture below f/5.6 when zoomed in (or f/3.5 when zoomed out) so I cannot create a nice DOF. Also, my kit lens has its sweet spot around f/7.1 and since I want my pictures to be sharp I want to shoot with that aperture.

So my basic questions are:

Do I need a new lens with a maximum wider aperture to achieve the outcome I want?

Does focal length really influence DOF? If so, why can't I change DOF by getting closer to the object? Am I doing something wrong?

I'm interested in street (especailly at night)/landscape and animal photography and my body is a Canon E550D RebelT2i (crop factor 1.6).

Thank you in advance!

Answer

For example, if you take a picture very close to an object, zoomed out, and then move further back and zoom in would the pictures show the same DOF given the aperture was adjusted?

DOF will almost certainly not be the same. You're right to point out that your lens (1:3.5-5.6) will automatically adjust its aperture as you zoom. If you make no other compensation, this will adjust your exposure, so to keep consistent exposure you should also adjust shutter speed or ISO to offset the aperture change invoked by zooming - but that's a side point.

The depth of field is proportional to the distance from the subject. So if you had a lens that had a fixed maximum aperture throughout its zoom range, then under your scenario (stand near, take a shot, step back some way, zoom in, take shot with same framing) - the depth of field will be different. To give you an example with some dummy numbers to give you a sense of what's going on - if you shoot a face from 1 metre at f/2.8, you might have a depth of field that's in focus approximately 1cm from front to back. Now walk back 10 metres, zoom in and take another shot at f/2.8 and your depth of field might now be 5cm or something like that. In the first shot, only the eyes are in focus. In the second shot, so is the nose and so are the ears.

So in your case where the aperture is adjusting, you can almost certainly guarantee the depth of field will not be the same simply because for your second shot the aperture will almost certainly be the same at 10m and 20m but different at 1m. So from 1 to 10m you might fluke it and get the same DOF, but from 10m to 20m you cannot.

so I cannot create a nice DOF

You need to tell us what you consider "nice". Shallow? Or deep?

my kit lens has its sweet spot around f/7.1 and since I want my pictures to be sharp I want to shoot with that aperture

Ok - that's a great starting point. If we know we want that fixed, then we also know from earlier in my answer we can still adjust depth of field by moving toward the subject, or away from it. If you fix your aperture then walk towards and away, find the closest and furthest distances from your subject that make great compositions for you - then inspect the images closely on a PC screen to see the difference in depth of field.

Do I need a new lens with a maximum wider aperture to achieve the outcome I want?

It depends on the outcome you want. A wider aperture will allow shallower depth of focus. A second benefit to wider aperture - even if you stop it down to f/7.1 (although a different lens will have a different sweet spot) is that your auto focus system uses all available light with the aperture wide open. This means in low light your AF will perform better on a lens supporting wider aperture - even if at time of exposure you program it to stop down to a small aperture.

Does focal length really influence DOF? If so, why can't I change DOF by getting closer to the object? Am I doing something wrong?

It's not focal length, per se, but it is distance to subject. The depth of field can in fact be calculated based on your distance from subject - there are websites where you can key in various values and measures to do this, but I don't have a link to hand. Moving closer - while retaining the same aperture - will make your DOF shallower. Perhaps your camera's adjustment of aperture due to zoom is offsetting this. You can test this by taking 2 shots from different distances without adjusting focal length (ie. without using zoom) between shots.

I'm interested in street (especailly at night)/landscape and animal photography

Very cool :) But even knowing your preferred subject matter doesn't tell me what kind of shot you'd like to take :) Hope the above gets you on your way though!

What type and capacity of memory card is supported by Canon 500D?

I was going to buy a new memory card for my Canon 500D and I was wondering if SanDisk Extreme III SDHC Card 8GB which has a write speed of 30MB/s would be a good buy. How can I find out if my camera supports 8GB cards and can make use of 30MB/s speed? The price difference is not really that much.

Answer

The Canon 500D takes SDHC cards up to 32gb. Any Class 6 or above will make sure that there is never a slow down from the cameras buffer filling up, and the 30MB/s card you mention is a Class 10 card so plenty fast. I just bought two of those myself to replace my 16gb PNY as I get a bit of slow down shooting raw occasionally

astrophotography - Star photography: what aperture

I would like to shoot the Andromeda galaxy with my 70-200 F2.8.

I do have a star tracker (not soo precise).

In general for faint things it is better to use a wide aperture, to gather as much light as possible. but given that the galaxy is RELATIVELY small with a 200 mm and I have to crop a lot, would it be better to shoot it at the lense's sweet spot to get maximum sharpness, and take more shots to combine in deep sky stacker? or will i miss all the very faint details?

Answer

There are at least two ways of looking at a lens' sweet spot. One is in terms of absolute acutance when measured after very careful manual focusing on a well lit test chart. Another is in terms of Depth of Field sufficient to cover errors introduced by autofocus inaccuracy. But DoF will affect results due to focusing errors much more at very short focus distances than at very long focus distances such as several million light years. At such long distances the accuracy of the focusing matters more.

In the case of astrophotography you're almost certainly using careful manual focus because AF doesn't usually work with stars and deep space objects such as distant galaxies. With the short throw of the focus rings on modern AF lenses the variation there between your best and worst manual focusing efforts will likely far exceed the difference between the lens' acutance at f/2.8 and at f/3.5 or f/4 or f/5.6 or wherever the absolute sweet spot of the lens is in term of aperture.

So until you can consistently focus your lens at deep sky objects with a very high degree of consistency what aperture you use really doesn't make much of a difference in terms of absolute sharpness. Unless you have a very precise tracking mount the shorter exposure time afforded by the wider aperture will likely lead to better results than using a longer exposure time with a narrower aperture and allowing tracking errors more influence on your result.

storage - How can I backup my photos while travelling?

I'm going travelling around the world for a year in September and am already panicking about how best to send my photos home while in various countries.

Requirements:

• I only need to backup JPEG files (I don't shoot RAW but that's another thread ;) )


• I need to be able to upload in a web-based manner (I will be using Internet cafes and so can't assume I can use FTP etc)


• I need plenty of space, preferably unlimited (I racked up about 200GB last year)



• I need to store the full image (no lossy compression is acceptable!)

Options I can think of:

• Burning and posting DVDs (can I trust these in the post and not to get corrupt? It may be better than waiting for upload speed though...)


• Flickr (I have a pro account but not sure how hard it'll be to get the photos back down again. Will I even be able to get the original snaps?)


• Setting up a server at a friend's house and hosting some kind of file server with a web-app front end

What have other people done? Or does anyone else have a better idea?

Answer

Depends on how much you value your shots. Last year my wife and I took a 5 month photographic trip and we took:

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  1 Laptop: We had Lightroom to download and do a basic selection every night (out of focus pictures don't need to take any disk space!). Photoshop to do some basic retouches if we wanted to publish them on Flickr, etc. And a large enough HD to store the whole trip.

  
  


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  6 4GB memory cards: we numbered them and made sure to rotate them correctly so we kept the pictures in there the longest possible time as backup. We rather use more cards with less GB to diversify risk. If you are in the middle of nowhere and your only 16 GB card breaks you are SOL.

  
  


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  2 300GB USB HD: once the pictures were classified on the laptop we backed them up to one drive and mirrored on the other.

  
  
  

Online storage is not practical when you are travelling because of the time it takes to upload the amount of data you will generate. This way we felt very confident that we weren't going to lose any data, at any given time pictures were stored in up to 4 different places at the same time.

And to send home, select up to 5 pictures of each escapade and post them on Flickr. Selection is key.