Is Depth Of Field Eye Dependent?

Discussion in 'Hunter (HFT) & Field Target (FT)' started by Jimbob 2705, Mar 8, 2015.

  1. Jimbob 2705

    Jimbob 2705 New Member

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    Hi All,

    Setting up my TX for HFT, which is currently fitted with a Hawke Sidewinder Tactical 4.5-14x42, which is a lovely scope BUT I'm finding that the DOF is terrible for me :(

    If I set it up for a 23 yard target (by my eye - not the range reading on the parallax), I lose the reticle at anything under 13 yards but also 45 yards are seriously blurred, as in very difficult to see the kill zone - Should point out I'm shooting at 10x magnification.

    So what I'm wondering is whether DOF is dependant on the individual? For example could someone else pick this scope up and find it completely different?

    Just I'm going to start looking at other alternatives, so just wondered if some scopes are known for having a narrow DOF, like my Sidewinder for example, or is it just a case of what suits your eyes?

    Now we're on the subject of HFT Scopes....:D:rolleyes:

    What is out there at 10x Magnification with a Half Mildot Style reticle (or similar, basically a reticle with half markings)?

    By choice I quite like having variable magnification and side parallax, but it's not an absolute necessity I suppose, just nice to be able to change the parallax when plinking.

    Many Thanks,

    James :)
     
  2. LANKY MK

    LANKY MK this **** is killing me.

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    Considering how many times I've looked through someone else's scope and got different DOF and vice versa I would say yes it's dependent on the individual.

    I get very little clear DOF with scopes set at 10 mag with 40+ objectives with 45y VERY blurred. 32 and 24 objective sizes help but there's still a fair amount of blur for me. Tried shooting low mag but prefer 10.

    Mark
     
  3. RobF

    RobF Administrator Staff Member

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    No, it's not otherwise everyone who looked through camera would get a differing view.

    What you could be seeing is the effect of having an eyebell set to a different setting than someone else.

    DOF is a function of the lens. The lenses present the image, the eye sees the image.
     
  4. Charlts

    Charlts Getting dusty

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    Why stick to 10x? Dropping the mag with increase dof.
     
  5. Jimbob 2705

    Jimbob 2705 New Member

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    Thanks for all the help everyone - really appreciate all the detail and help everyone is going into!

    I should of thought that the eye doesn't make much difference, it makes sense when comparing it to a camera lens

    Reason is that I just seem to prefer 10x, especially for further targets. Just I feel it helps me be more accurate when sighting in and just in general when shooting at distance, although I cojld sight at 10x and wind it down to 8x

    Regarding the crosshairs dissapearing - I feel like I have given false information, yes they dissapear but only when focusing really hard on the target (so the target turns clear)

    Looks like I should be looking at it the other way around - focus on the reticle and see how blurred the target is

    I think my issue is that as the target is so blurred (as in almost unshootable), I'm trying to focus on it to make it clearer and hence losing the reticle in the process

    I'll try it on lower magnification and see how I get on

    Out of interest, would the Hakwe Sidewinder Tactical 10x42 have a better DOF? Basically the fixed magnification of mine.

    Thinking about it, it probably would as you've got the same magnification and the same objective size...but I do hear people saying fixed power scopes are better...
     
  6. Adam

    Adam Active Member

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    Rob is correct. In an optical system, DOF is DOF. An image on a sensor or film is either focused or not.

    But while the human eye is viewing an image through an optical system, the eye forms part of the optical system. There is another lens (within the eye) and "sensor" (retina) in the mix.

    The human eye tries to make a blurry image clear, a process called accommodation. This ability declines markedly with age.

    So the apparent DoF of a scope is influenced by the individual using it.
     
    KeithW likes this.
  7. RobF

    RobF Administrator Staff Member

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    True. What accommodation does is allow the eye to shift the focus but it's really limited, it's going to be a hard task to make mega DOF disappear ;) :)

    The image plane is focused to one point, and I'm not sure this is really about DOF, but about the reticule being lost in favour of the image.

    If the eye is accommodating, ie shifting focus to the image, then it would suggest that perhaps the cross hairs are not set correctly for the eye. A little bit of fight between reticule and image can be experienced where the two are close in focus terms to each other ie say your shooting at 30yds and parallaxed to 25... however when the focus of the image is way off (ie close or far away) the eye should jump clearly to focus on the reticule, not the image... the ret shouldn't be lost.

    The image you see in a scope works like this...

    You have the image... what you're looking at... that is focused to a point inside the scope which if the parallax is removed is at the same place as the cross hairs inside the tube. If the object you are looking at is further back or forth than what the parallax is set to, the focus point of the image is behind or in front of the cross hairs, and that's why you get parallax error because the two are apart. Its a tiny amount in the scope (millimeters or less), but magnification magnifies the gap and effect.

    The eyebell adjustment focuses your vision to the cross hair. It should be repeatably in focus. Test it on high mag against a blank background so the eye isn't trying to accommodate another image and throwing your eye's focus behind or in front of the cross hairs.

    So in order to see the image correctly, you need to be able to see the cross hairs. Then you know your eye isn't doing any unnecessary work and you wont lose the ret, and the DOF is true or at least common to someone else to a correctly setup scope for them.

    What the eye bell adjustment can't cope with is eyesight beyond it's range of adjustment, or astigmatisms which means the eye doesn't settle in focus properly as it fights to focus vertical and horizontally due to it's oval shape of focus.

    You can test scopes side by side... stick a camera behind them...it will show the actual DOF of your scope, and you can compare with others if you like.
     
  8. DaveF

    DaveF Member

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    i now have 3 scopes Falcon menace 4-14 hawke airmax sf30 4-16 and delta optics 4-14 as a result of trying to find one that has a bigger depth of field at 10x or more mag. none achieve what I want clear at 12 -40 yards blur 10y and 45 yards most are clear at 18-35 yards only by dropping down to 8 mag will they achieve what I want

    Smaller objective lenses scopes appear to give grater depth of field
    a
    The mtc connect seems to have best depth of field at 10+ mag I have tried but the ret is to fine for me and not ideal for people with glasses

    I just looked through a vortex diiamond back and that does seem to have a greater depth of field at 10+ mag but the ret is no good for bracketing. going to try it out on a course to see if it really is better

    Dave
     
    Last edited: Apr 4, 2015
  9. tillygti6

    tillygti6 Tilly's gun stocks

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    I had both the fixed 10 hawke tac 30 and the adjustable mag one, the dof to my eyes was better on the fixed 10. But even better still on the panorama. 4-12x40.
    I now have a pair of panoramas. I really like them.

    I did have a bushnell elite firefly Scope which had an unusually long dof but the reticule wasn't ideal.

    It can get very scientific why and how.but it's well over my head.
    So I can't even pretend to know why they vary so much.
    simple options to look through as many scopes as possible.
     
  10. KeithW

    KeithW Barn door? Where?

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    My eyes really struggled with the TAC 30 one way or another (even though it is a "great" scope for many people). I have happily used the MTC Connect-24 which has a v good depth of field but also has a fine reticle that i struggle with sometimes when my eyes are playing up. However I am finding the Nikko Stirling Gold Crown Airking suits me eyes very well: a bright image, great depth of field, very managable parallax (I seldom miss close targets) and a ret which is thick enough for me to see.

    Many shooters will tell you it is too cheap to be any good, but I got an HFT PB of 57 the other week using it, and tied with 3 really really good shooters for 2nd highest score, one point below the winner in a field of 90 - so I have no complaints!
     
  11. DEAN C.

    DEAN C. Steyr Convert

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    Dont forget that adjusting the PX distance and the rear ocular just in small amounts will make big differences to what you see regarding the ret and focus at different ranges.
    Ive had quite a lot of scopes and think a fixed 10 mag is generally slightly better regarding DOF, depending upon the scope of course. I used a 4x12x40 panorama on my Pro Sport for the PJBRC and was pleased with the results, but my Hawke TAC 30 10x42 is better glass altogether. My favourite HFT scope is still my Sightron 10x42 with rear PX and Half mildot, also EB snipers are worth a look if you can manage with a standard mildot ret and the MTC Viper takes some beating as well especially for the price.
     

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